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351W will not rev past 4000rpm - ideas?

Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=47540
Printed Date: March-28-2024 at 8:51pm


Topic: 351W will not rev past 4000rpm - ideas?
Posted By: zwoobah
Subject: 351W will not rev past 4000rpm - ideas?
Date Posted: June-02-2019 at 9:19pm
'68 Mustang with a mid-70s wintage 351W. Holley 4160 carb and MSD blaster coil/wires.

Finally got a working tach installed today. Boat pulls strong until 4000rpm and then stumbles/will not rev higher. This equates to 41mph on GPS.

Diagnostic plans for next weekend:
1. New inline fuel filter. Tank definitely has some rust in it.
2. Get boat warmed up and then unplug auto choke. Choke is wired in with the 12v supply to the coil. Coil does have a resistor.
3. Maybe new dist cap/rotor? I have no maintenance history on these. Can anyone identify my distributor?

Anything else I should tackle? The boat is on a lake 2.5hr away, so I need to order parts ahead of time and bring them with me.







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1968 Mustang 16 - 351W powered



Replies:
Posted By: jimsport93
Date Posted: June-02-2019 at 9:42pm
What prop are you spinning ?


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http://www.correctcraftfan.com/diaries/details.asp?ID=2798 - 93 Sport Nautique


Posted By: 8122pbrainard
Date Posted: June-02-2019 at 9:42pm
Chris,
Describe the "stumble". Does the engine seem to falter/miss or will it just not get past the 4000 rpm? You got the boat in October so have you had it out on the water much or is this the first time? I ask since if it is the first time and the engine just won't get past the 4000, I wonder how it's propped. What prop is on it?

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64 X55 Dunphy

Keep it original, Pete
<


Posted By: KENO
Date Posted: June-02-2019 at 10:32pm
Originally posted by zwoobah zwoobah wrote:

'68 Mustang with a mid-70s wintage 351W. Holley 4160 carb and MSD blaster coil/wires.

Finally got a working tach installed today. Boat pulls strong until 4000rpm and then stumbles/will not rev higher. This equates to 41mph on GPS.

Diagnostic plans for next weekend:
1. New inline fuel filter. Tank definitely has some rust in it.
2. Get boat warmed up and then unplug auto choke. Choke is wired in with the 12v supply to the coil. Coil does have a resistor.
3. Maybe new dist cap/rotor? I have no maintenance history on these. Can anyone identify my distributor?

Anything else I should tackle? The boat is on a lake 2.5hr away, so I need to order parts ahead of time and bring them with me.








Unplugging the choke will be the wrong thing to do because without 12 ish volts going to it, it will want to go shut and the engine will run like crap to put it in plain easy to understand english. It's normal to be wired with the 12 volt supply to the coil.

The distributor is a Prestolite with the clip down cap and the 2 wires coming out of it tells me that you have an electronic module under the cap

In no particular order I'd be figuring out what the prop dimensions are, checking the timing at idle and seeing that it advances with RPM and seeing what your total advance is.

Commander has that distributor advance spec at 6 degrees BTDC at idle of 600 -650 rpm or so and that will probably give you a total advance around 30 or so.

If you bump the initial up to 10 to 12 degrees that'll add 4 to 6 degrees to the total and improve things. Around 34 is good for total advance, 36 if you want to push it and use good gas.

Check the springs/flyweights under the advance mechanism to be sure they're not rusted and/or stuck or broken and limiting your advance.

You could also verify that the secondaries open. You have to do this under load on the water.Here's a link below that will tell you how to easily check the opening and it'll also tell you that they won't fully open with a 600 Holley on a 351

http://www.correctcraftfan.com/forum/forum_posts.asp?TID=41479&title=holley-secondaries-issues" rel="nofollow - link


Posted By: KENO
Date Posted: June-02-2019 at 10:41pm
You could also post the list number on the air horn on the carburetor or better yet post a picture to figure out just what you have there.

Here's a picture to show where the list number is.

Somebody's bound to ask if it's a marine carburetor and the list number will tell if it is.





Posted By: zwoobah
Date Posted: June-02-2019 at 11:02pm
Jim/Pete/Ken - great suggestions, thanks.

I think the prop is stock. I’ll check for markings next weekend.

I’ll bring my timing light up to the lake next week and will fiddle with the timing a bit. I always run 93 octane in my toys as most of them require it. I’ll also order a new cap/rotor.

I’ll also have a passenger check my secondaries and will get the carb numbers. The carb was rebuilt last summer by a friend of the previous owner, so hopefully it just needs a bit of adjustment.

Pete - you are right, I’ve only owned the boat a short time. I’ve put seven hours of run time on it so far, mostly this spring. Currently it sputters at 4000rpm and will not go any further while under load. This feels like an engine issue more than a top speed/prop issue. It comes out of the hole OK but doesn’t slam me back in the seat.

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1968 Mustang 16 - 351W powered


Posted By: MrMcD
Date Posted: June-03-2019 at 5:00am
A couple more things to ponder. Are the 4 barrel secondaries opening?
How old is the gas in that boat, with all the sitting you may be trying to run it on 2 year old gas.
When you hook up the timing light verify that your timing does advance as it is supposed to. Set your timing at idle as already instructed and then increase RPM slowly while watching your timing marks, you should see the timing advance smoothly as you increase the RPM. It will stop advancing somewhere between 3,000 and 3,600 most likely but if you do this record what you see.   A dial back timing light would allow you to know exactly how much advance you have.
A little rust can really mess up your distributor advance mechanism but is easy to fix.

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Posted By: KENO
Date Posted: June-03-2019 at 7:48am
Originally posted by MrMcD MrMcD wrote:

A couple more things to ponder. Are the 4 barrel secondaries opening?
How old is the gas in that boat, with all the sitting you may be trying to run it on 2 year old gas.
When you hook up the timing light verify that your timing does advance as it is supposed to. Set your timing at idle as already instructed and then increase RPM slowly while watching your timing marks, you should see the timing advance smoothly as you increase the RPM. It will stop advancing somewhere between 3,000 and 3,600 most likely but if you do this record what you see.   A dial back timing light would allow you to know exactly how much advance you have.
A little rust can really mess up your distributor advance mechanism but is easy to fix.


You really should read the whole thread before giving him some more things to ponder, which have already been mentioned


Posted By: zwoobah
Date Posted: June-03-2019 at 3:40pm
Follow up: If the secondaries are not opening, what do I adjust?

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1968 Mustang 16 - 351W powered


Posted By: MrMcD
Date Posted: June-03-2019 at 5:10pm
If the boat stumbles as mentioned at the beginning at 4,000 RPM or so it is not the 4bbl not opening.   You can run it on 2 barrells and it will run perfect at all speeds, it will just be down on power at high RPM.
Maybe as much as 25-30%.   You would not notice till you try to accelerate real hard.

You asked how to check to see if the 4bbl is opening.
If you are on the lake, lift the engine cover and have the passenger watch the 4 bbl as you accelerate. You should hear and see the secondary open.
A vacuum pot will pull up on the secondary at wide open throttle. It must be under load for this to happen.   If it does not open you can turn it open manually while accelerating on the lake to see if your power picks up like normal.

Starting to run bad at 4,000 RPM indicates other issues.
I would still start by confirming the distributor is working correctly and the advance is giving you proper timing maxing out as stated already in this forum to be 34, safe 36 on the max side.


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Posted By: 63 Skier
Date Posted: June-03-2019 at 7:11pm
Originally posted by KENO KENO wrote:

Originally posted by MrMcD MrMcD wrote:

A couple more things to ponder. Are the 4 barrel secondaries opening?
How old is the gas in that boat, with all the sitting you may be trying to run it on 2 year old gas.
When you hook up the timing light verify that your timing does advance as it is supposed to. Set your timing at idle as already instructed and then increase RPM slowly while watching your timing marks, you should see the timing advance smoothly as you increase the RPM. It will stop advancing somewhere between 3,000 and 3,600 most likely but if you do this record what you see.   A dial back timing light would allow you to know exactly how much advance you have.
A little rust can really mess up your distributor advance mechanism but is easy to fix.


You really should read the whole thread before giving him some more things to ponder, which have already been mentioned


I'm with Ken x2! And he didn't ask how to see if secondaries are opening, he asked what to do if they don't!

I'm putting my 14 cent bet on distributor advance hanging up after partially advancing. Follow all the great advice above and I don't believe this will be a hard one to get straightened out. And then I'll be anxious to hear how the 16' boat is responding to the 351!

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'63 American Skier - '98 Sport Nautique


Posted By: 8122pbrainard
Date Posted: June-03-2019 at 8:30pm
Originally posted by 63 Skier 63 Skier wrote:

   I'll be anxious to hear how the 16' boat is responding to the 351!

Me too!!

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Keep it original, Pete
<


Posted By: KENO
Date Posted: June-03-2019 at 10:10pm
Originally posted by zwoobah zwoobah wrote:

Follow up: If the secondaries are not opening, what do I adjust?


One thing you could do is look at the instructions in the link below and pay special attention to the part about restricting orifice / ball check valve. Some have the orifice, some have the ball check. Sometimes people unknowingly lose the ball when they take it apart Page 13 and 14 talk about vacuum secondaries and their disassembly /reassembly. There's a little cork gasket that can get squashed and block the sensing passage or get left out and affect the vacuum signal to the diaphragm

https://documents.holley.com/199r7948-5rev6.pdf" rel="nofollow - link

But ...............also what you should really do is get one of the dozen or so Holly Carb Tuning Books that are available.. Click on the link below to see some of them

You'll learn a lot from any of them. Plenty of pictures and good explanations and exploded views

Should probably mention also that the diaphragm can be torn/cracked

https://www.google.com/search?ei=42T1XPn4Kc6m_QbqzrGgCg&q=holley+carb+tuning+books&oq=holley+carburetor+tuning+books&gs_l=psy-ab.1.0.0i22i30l2.7227.14815..18867...0.0..0.147.1600.0j12......0....1..gws-wiz.......0i71j0.PPwLNmZtKnE" rel="nofollow - link



Posted By: 8122pbrainard
Date Posted: June-03-2019 at 11:41pm
Originally posted by MrMcD MrMcD wrote:


If you are on the lake, lift the engine cover and have the passenger watch the 4 bbl as you accelerate. You should hear and see the secondary open.
A vacuum pot will pull up on the secondary at wide open throttle. It must be under load for this to happen.


Chris,
Unless I missed something, you haven't mentioned how you checked to see if the secondary is opening. As Mark mentions, the engine needs to be under load.

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/diaries/details.asp?ID=1622" rel="nofollow -

54 Atom

/diaries/details.asp?ID=2179" rel="nofollow - 77 Tique

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Keep it original, Pete
<


Posted By: zwoobah
Date Posted: June-04-2019 at 1:06am
Thanks everyone.

Here’s my plan:
1. Replace inline fuel filter
2. Check that secondary diaphragm is intact
3. Check idle and 3600rpm timing, adjust to 10btdc at idle
4. Check advance mechanism/springs and cap/rotor
5. Check that choke plate opens fully after key is switched on for a bit
6. Use the zip tie method that Ken posted to see if secondaries are opening under load

Hopefully this will get her straightened out. She starts and runs sweet.

What is the recommended redline on this motor? Just a bit over 5000rpm? Supppsedly it was installed in the mid-70s after the original 289 froze and cracked during winter. I have no details on cam or valve springs.

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1968 Mustang 16 - 351W powered


Posted By: MrMcD
Date Posted: June-04-2019 at 1:41am
My 78 Nautique 351W had a max RPM listed on the valve cover of 4,600 if my memory is correct.
With a set of performance heads I ran that engine many times up to 5,300+.
With a 13x14 prop MPH was above 50, almost 55.   The rest of this engine was stock.
I sold it with 1,500 hours on it still running very strong. Put the new heads on at 900 Hours.
A good running 351W should give your boat a lot of pop.

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Posted By: KENO
Date Posted: June-04-2019 at 8:10am
Originally posted by 8122pbrainard 8122pbrainard wrote:

Originally posted by MrMcD MrMcD wrote:


If you are on the lake, lift the engine cover and have the passenger watch the 4 bbl as you accelerate. You should hear and see the secondary open.
A vacuum pot will pull up on the secondary at wide open throttle. It must be under load for this to happen.


Chris,
Unless I missed something, you haven't mentioned how you checked to see if the secondary is opening. As Mark mentions, the engine needs to be under load.


Well Pete, you did miss something since he hasn't checked yet.


Posted By: TRBenj
Date Posted: June-04-2019 at 9:21am
#1 is a good idea if condition is unknown.

So is checking the initial and final timing. Set initial to dial in the final... 34 or so being ideal. 10-14 on the initial will usually runnpretty good... but depending on how much advance you’re getting, you may need to compromise on those numbers. Just don’t exceed 36 total.

On the secondaries, all those checks are fine I guess, but the first 2 things I’d do would be to check and see if the butterflies are stuck (and how they feel when moved if not) - this can be done engine off. If all seems fine then go for a ride and see if they’re getting pulled in by inspecting. This requires a helper and reasonably calm water. Operate them manually if they aren’t working or weak (not pulling in all the way). This will tell you what to focus on for the fix.


Posted By: zwoobah
Date Posted: June-04-2019 at 11:08am
Thanks Mark. I’ll keep her under 5000 until I feel her out.

Ken/Pete - my boat is 2.5hr north, wont be able to check anything until this weekend :)

Tim - good point, I’ll move the secondaries by hand first. I’m not crazy about the idea of going down the lake at 35mph with my engine cover open. It sits up pretty high and will catch a ton of wind. Gonna try the zip tie method first, if that doesn’t give clear results I’ll remove the engine cover and get eyes on the secondaries.

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1968 Mustang 16 - 351W powered


Posted By: 63 Skier
Date Posted: June-04-2019 at 11:23am
Removing the engine cover solves the wind issue, and makes all this diagnosis really easy.

If you don't mind my asking, where do you keep the boat?

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'63 American Skier - '98 Sport Nautique


Posted By: zwoobah
Date Posted: June-04-2019 at 12:03pm
Boat is in Wakefield NH

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1968 Mustang 16 - 351W powered


Posted By: MrMcD
Date Posted: June-04-2019 at 2:31pm
My 78 was a Ski Nautique and the cover may be a little smaller than your cover.
I did run it several times with the cover up as I worked out problems with a Holley 4bbl.   Finally got it dialed in with the 4bbl opening on time as needed and never had to do it again.   My lake is only 10 minutes away so taking it out for a test run was not a big deal.

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Posted By: TRBenj
Date Posted: June-04-2019 at 2:52pm
Originally posted by zwoobah zwoobah wrote:

I’m not crazy about the idea of going down the lake at 35mph with my engine cover open.

To each his own, standard practice for troubleshooting a problem like that here. Have done it many, many times. One quick ride gets you pointed in the right direction.


Posted By: KENO
Date Posted: June-04-2019 at 5:03pm
I thought I'd stay out of the engine cover discussion and ask if you know how to check that the secondaries will open by hand when the engine is OFF?

I'd tell you how but you may already know. And besides 2 more people would give you the same answer right after I did that.

I'll save my breath for now.

And no need to ask anything like "why won't my engine hit 5300 rpm" like MrMcD's obviously super powerful 351 that was turning a 13X14 prop at that speed and going 50 to almost 55 mph. That tells me he had some terrible prop efficiency with 22% slip at best..

The run of the mill 240 HP 351w from PCM, Indmar etc has a max of 4400 rpm but a little higher isn'r gonna hurt it. Your engine will be happy at 4500 rpm.if it's stock

Maybe his tach read high



Posted By: MrMcD
Date Posted: June-04-2019 at 5:38pm
Keno, my 78 did run great, the heads bumped compression quite a bit with small chambers but they were professionally ported with big valves, came off a friends race motor, it needed premium fuel but it ran great. Pinged like crazy on regular.
I did not have GPS in 1982 and who knows if the tach or speedo was accurate
The owner of West Coast Correct Craft ran a Nautique with a 454 back then and I walked him more than once crossing Folsom Lake in the evenings after work.
He tried more than once and never outran me. His was a 1981, I think it had the same exact hull as my 78.
We would ski or barefoot till dark and then make the fast dash accross the lake to the dock.
His was stronger pulling barefooters although my 351 easily pulled my buddy who liked to one foot at 43 mph. His new at the time 1982 351 powered 351W stock could not do that.
The older hull rides like a brick but they are lighter and faster than the newer hulls a 13x13 ran the RPM too high for me so I used the 13x14 and liked it a lot. We ran at 500-1500 elevation most times.

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Posted By: KENO
Date Posted: June-04-2019 at 10:04pm
Originally posted by MrMcD MrMcD wrote:


I did not have GPS in 1982 and who knows if the tach or speedo was accurate
.


This says quite a bit

Not doubting that it ran good, the numbers just don't work out



Posted By: davidg
Date Posted: June-06-2019 at 1:07am
Interesting thread. My '87 Martinique w/ PCM 351 W has this exact problem, except mine stumbles a bit on initial acceleration, and not at 4000 rpm. I need to check my acceleration pump.

When I give it full throttle, it tops out at 4000 rpm with Acme 542 prop. I "assumed" my secondaries were opening, but, this thread is making me rethink that. The engine runs perfectly other than this. As Mr. McD says, these engines will run perfectly on 2 bbls, and even accelerates real good for a bigger boat.

I really don't get on it that often to even need the four bbl. I'm running at around 2500-3000 rpm most of the time just skiing or cruising. But, if it's broke, I still want to fix it.

What have you guys found that are the top reason or two the secondaries don't open?


Posted By: zwoobah
Date Posted: June-10-2019 at 11:58am
Did some tinkering this weekend.

Changed the fuel filter, checked and oiled the advance mechanism, checked the secondaries.

Good news - the boat now revs to 4,700rpm smoothly. This equates to 43mph. The secondaries open about 70%. I have the Pertronix ignition module - seems to be working fine.

Bad news - I have no idea what fixed it.

My timing light crapped out after two flashes so I wasn't able to check or adjust timing. Will get a new one and try again next weekend.

Prop is a 13x13 and the carb numbers are in the photo below.

There's a vacuum line coming off the carb that isn't attached to anything. Where is this supposed to go?











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1968 Mustang 16 - 351W powered


Posted By: TRBenj
Date Posted: June-10-2019 at 12:16pm
43 with a 351w in that hull? You’re missing at least 5mph... I’d start with the prop but don’t see any mention of timing numbers? Also check if that carb is marine.


Posted By: KENO
Date Posted: June-10-2019 at 12:38pm
Originally posted by TRBenj TRBenj wrote:

43 with a 351w in that hull? You’re missing at least 5mph... I’d start with the prop but don’t see any mention of timing numbers? Also check if that carb is marine.


What he said

Or I could tell you that the carburetor is a 600 cfm Holley Street Warrior carburetor.

And you probably know there are no streets on the water

It'll work OK, it just doesn't have marine leakage protection (and certification) which could lead to a fire/explosion


Posted By: zwoobah
Date Posted: June-10-2019 at 12:55pm
Yes, I was hoping for 50mph. I did have three people in the boat and a full tank, but still seems slow. The bulb in my timing light crapped out after two flashes so I couldn't do anything with timing. Will bring up another light next weekend.

Existing prop is a 13x13 Michigan Wheel Dyna Jet. What would you suggest for a prop?

Number on the carb air horn comes up as a 600cfm Holley 4160 but I can't find any data on whether it's auto or marine. It was rebuilt last summer so I don't want to replace it. Could that mystery hose be the fuel pump overflow hose?

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1968 Mustang 16 - 351W powered


Posted By: KENO
Date Posted: June-10-2019 at 12:58pm
Click on the link and you won't find anything calling it a marine carburetor

https://www.google.com/search?ei=a2X-XL7ZJ-HF_Qbq1IiIAw&q=holley+80457-3&oq=holley+80457-3&gs_l=psy-ab.1.0.0l2j0i22i30l4.23244.23244..26129...0.0..0.106.106.0j1......0....1..gws-wiz.......0i71.U6aPdiMSLuo" rel="nofollow - link

Somebody probably bought it because it was a lot cheaper than the marine one


Posted By: 8122pbrainard
Date Posted: June-10-2019 at 12:59pm
Originally posted by zwoobah zwoobah wrote:


Number on the carb air horn comes up as a 600cfm Holley 4160 but I can't find any data on whether it's auto or marine. It was rebuilt last summer so I don't want to replace it.

Originally posted by KENO KENO wrote:



the carburetor is a 600 cfm Holley Street Warrior carburetor.

And you probably know there are no streets on the water

It'll work OK, it just doesn't have marine leakage protection (and certification) which could lead to a fire/explosion


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/diaries/details.asp?ID=1622" rel="nofollow -

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/diaries/details.asp?ID=2179" rel="nofollow - 77 Tique

64 X55 Dunphy

Keep it original, Pete
<


Posted By: zwoobah
Date Posted: June-10-2019 at 1:16pm
Any idea what the hose is for on the carb? It's just hanging down to the side currently

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1968 Mustang 16 - 351W powered


Posted By: KENO
Date Posted: June-10-2019 at 3:40pm
Originally posted by zwoobah zwoobah wrote:

Any idea what the hose is for on the carb? It's just hanging down to the side currently


The fitting taps into the airspace above the secondary throttle plates, the hose hooks to that and the other end hooks to the little air inbleed for the electric choke which is under a vacuum.

On a car it provides clean air from inside the air cleaner to the electric choke for proper operation.

On a marine 4160 the little air inbleed has a small brass screen, since there's not a lot of dust and dirt out on the water.

In the link below, look at page 4 figure 2A and also page 9 figure 8 and you can see it's routing

https://www.jegs.com/InstallationInstructions/500/510/510-0-80457S.pdf" rel="nofollow - link


Posted By: KENO
Date Posted: June-10-2019 at 3:47pm
This picture was in the thread about checking secondary operation with a zip tie but it also shows the air inbleed fitting to the choke right in front of the secondary lever with the zip tie.

It's the brass tubing fitting and there's a little screen in there.



Posted By: zwoobah
Date Posted: June-10-2019 at 6:00pm
Thanks Ken! I'll check that the screen on the choke air intake is in place, and if it's there I'll remove the hose and cap the other port.

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1968 Mustang 16 - 351W powered


Posted By: MrMcD
Date Posted: June-10-2019 at 6:22pm
Glad you are getting it running better.
Did you verify your speedometers with a GPS???

Maybe you were going faster. As I recall, and it has been a long time the 13x13 prop gave speed readings that are very close to actual RPM, so 36 mph = 3600 RPM. I would think you are close to 47 mph if your prop is good.   Still room to improve but you are much better than the original 4,000 RPM.

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Posted By: zwoobah
Date Posted: June-10-2019 at 6:25pm
I don't have a speedometer on this boat, so I measured my speed with a GPS app on my phone.

Also verified that my hour meter is unreliable - which makes sense, given that it shows 27 hours on a 1968 boat. Likely going to replace it with a 2" GPS speedometer.

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1968 Mustang 16 - 351W powered


Posted By: tryathlete
Date Posted: June-10-2019 at 8:35pm
I’m betting the oil on the distributor advance mechanism was your fix. It was rusty and now it’s free to give you the advance you were missing.


Posted By: TRBenj
Date Posted: June-10-2019 at 9:14pm
13” diameter prop is too big for that hull. That and if it’s turning 4700rpm and only producing 43mph would mean it’s time to put it on the mantle. Acme 1214 would match the powertrain and hull much better.

Not all apps are created equal. Navionics.

Once you have at least 2 out of 3 known good pieces/measurements (known good prop, accurate tach and accurate speed) then we will actually be able to tell how well your boat is running. I suspect you are 0/3 at the moment.


Posted By: MrMcD
Date Posted: June-10-2019 at 11:08pm
Tim, are you thinking the large prop on the old boat is running too close to the hull?
Causing friction? Just curious, I don't know the old hull at al I was thinking it was similar to the Ski Tique hull, 16" version of the Nautique.

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Posted By: KENO
Date Posted: June-10-2019 at 11:59pm
Originally posted by zwoobah zwoobah wrote:

Thanks Ken! I'll check that the screen on the choke air intake is in place, and if it's there I'll remove the hose and cap the other port.


One of those little voices in my head keeps saying that you're gonna justify in your mind why it's OK to use an automotive carburetor

It may have worked for a number of years, but it's not the safest way to go.

You should also check the fuel line from the pump to the carburetor to see if it has a USCG A1-15 rating or if it's regular automotive line

Here's a link to an old thread with lots of "discussion" about fuel lines .

Tank to pump should be USCG rated stuff too.

http://www.correctcraftfan.com/forum/forum_posts.asp?TID=38399&title=holley-4160-bowl-screws-stuck" rel="nofollow - link

Just tryin' to keep ya safe and out of the burn ward.


Posted By: TRBenj
Date Posted: June-11-2019 at 12:11am
Originally posted by MrMcD MrMcD wrote:

Tim, are you thinking the large prop on the old boat is running too close to the hull?
Causing friction? Just curious, I don't know the old hull at al I was thinking it was similar to the Ski Tique hull, 16" version of the Nautique.

The 13” diameter is unlikely to cause major performance issues but will definitely harm the hull if used long term (months). Since it appears to be performing like garbage anyways, all the more reason to retire it.


Posted By: MrMcD
Date Posted: June-11-2019 at 4:45am
Thanks Tim,
In the 80's a boat builder in Sacramento released a boat called the Keaton Utility, made by Jack Keaton, Jack had a friend that was a competitive barefooter so Jack modified a hull he originally had out in the early to mid 60's also known as the Keaton Utility for barefooting and skiing, updated his interior and started selling it again in the 1980's.
It was an 18' boat, 350 Chevy powered, mid engine like our Nautiques.
I skied wth two guys that had them in the 80's.
Jack used less angle on the prop shaft and ran a 12 x 15 3 blade back then.
The 350 GM was rated 260 HP and those boats ran 55 MPH.
They had a flat hull and would get up on plane like the old speed boats.

My 78 Nautique was about 1-2 mph short of them when we raced.
I think my 351W was 270 to 300 HP but it was not enough against these boats..
Since a 260 HP Chevy was able to spin that 12x15 prop and go so fast I am wondering how it would do on this Old Hull in this post.
In the old days, 60's and 70's Jack would sell you his boat and it was up to the buyer to find and install an engine. Because of this there are Keaton Utility's running around with 440 Chryslers, 327 Chevys, 383's, 390 Fords. 430 Mercs, Flat bottom so they ran fast but rode rough and did not hold well to hard skiers in a course, good barefoot boats though.
Jack ran a first class shop. He also built an 18' Jet that won Powerboat magazines Boat of the Year award in the late 70's when Jet boats were Hot.
Since his manufacturing was in Sacramento there are many of his boats still out on our waters today. That is a lot of words to ask your thoughts on trying a 12x15 prop.
http://keatonboat.com/images/Tournament_pictures/IMGP0678.JPG

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Posted By: 8122pbrainard
Date Posted: June-11-2019 at 6:47am
Originally posted by MrMcD MrMcD wrote:

Tim, are you thinking the large prop on the old boat is running too close to the hull?
Causing friction? .

Originally posted by 8122pbrainard 8122pbrainard wrote:

Greg,
Hull rash is caused by cavitation, When the prop blade tips run close to the hull, certain conditions form a negative (vacuum) condition. This vacuum causes the water to change state to a vapor form in tiny bubbles. (steam at a low temperature) This change of state creates tiny implosions which in turn create tiny vibrations, These vibrations in time break down the gel/glass surface. An analogy would be a tiny jack hammer chipping away eroding the hull. The same thing happens on pumps when the suction side is starved and the vacuum is formed eroding volutes and housings.


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/diaries/details.asp?ID=1622" rel="nofollow -

54 Atom

/diaries/details.asp?ID=2179" rel="nofollow - 77 Tique

64 X55 Dunphy

Keep it original, Pete
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Posted By: TRBenj
Date Posted: June-11-2019 at 8:51am
An acme 1214 is 12.5x13 and runs very similar revs up top as a 12x14 Oj 3-blade or a federal 12x15. So yes those are the 3 worth trying on this small/light hull with 350ish ci. The acme will run the best of the 3... I own them all and that’s what I run on my 331ci 16’ Skier. We have a few other similar data points, including Alan’s hurricane, Reid’s 347ci Mustang, and Andy (leftfield’s) 351w Ski Tique.

I’ve always liked the look of the Keaton’s... but had assumed they were older (60’s vintage) based on the styling. Didn’t realize they were fast... but if they were light and rode bow high with shallow strut angles, that’ll do it.


Posted By: MrMcD
Date Posted: June-11-2019 at 2:27pm
Jack started building Race Boats originally, he built family boats later.
He wanted all his designs to run fast. Sounds like you are all over the 12x15 prop theory.



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Posted By: zwoobah
Date Posted: June-12-2019 at 12:45pm
Will be headed back up this weekend. Don't have the budget to replace the carb at the moment, but I do want to make it as safe as possible.

Are there any local retailers who carry A1-15 fuel line? I'm betting it's got automotive line now. Definitely has automotive line and spring clamps at the fuel filter between the pump and carb.

I'll also order J-tubes and retrofit those to this carb.

Thanks for watching out for my safety. This is all new stuff for me.

Tim - I'll plan to buy a new prop at some point in the future. The current 13x13 seems to have an inch or so of clearance between the hull and prop. I don't see any signs of hull damage and the prop is tarnished enough to be pretty old. I'll get a better picture this weekend,

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1968 Mustang 16 - 351W powered


Posted By: KENO
Date Posted: June-12-2019 at 1:15pm
You'll probably pay thru the nose if you find some A1-15 locally.

Here's a place with reasonable prices for 3/8 A1-15. I'm sure there are others with reasonable prices too.

https://www.marinepartssource.com/marine-parts/fuel-systems/fuel-hose/3-8-low-permeation-marine-fuel-hose-per-foot-sierra-116-368-0380-1" rel="nofollow - link


Posted By: zwoobah
Date Posted: June-15-2019 at 2:09pm
Got the timing dialed in today - 10 at idle, 34 at 4000rpm. She starts much easier an now pulls to 45mph at 4900rpm. I checked my dash tach against my dwell tach and they are within 100rpm. Gonna run her this was for this season, plan for a new prop and maybe a new carb next summer. Thanks everyone for all the help. I’ve learned quite a bit.

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1968 Mustang 16 - 351W powered



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