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351W will not rev past 4000rpm - ideas?

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zwoobah View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zwoobah Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 10:55am
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?
1968 Mustang 16 - 351W powered
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 10:58am
Click on the link and you won't find anything calling it a marine carburetor

link

Somebody probably bought it because it was a lot cheaper than the marine one
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 10:59am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote zwoobah Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 11:16am
Any idea what the hose is for on the carb? It's just hanging down to the side currently
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 1:40pm
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

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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 1:47pm
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.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote zwoobah Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 4:00pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 4:22pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote zwoobah Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 4:25pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote tryathlete Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 6:35pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 7:14pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 9:08pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 9:59pm
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.

link

Just tryin' to keep ya safe and out of the burn ward.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: June-10-2019 at 10:11pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: June-11-2019 at 2:45am
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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Post Options Post Options   Thanks (1) Thanks(1)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: June-11-2019 at 4:47am
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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Post Options Post Options   Thanks (1) Thanks(1)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: June-11-2019 at 6:51am
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: June-11-2019 at 12:27pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote zwoobah Quote  Post ReplyReply Direct Link To This Post Posted: June-12-2019 at 10:45am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-12-2019 at 11:15am
I don't think J tubes would fit those slanted vents on your carburetor because of the slant.

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.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote zwoobah Quote  Post ReplyReply Direct Link To This Post Posted: June-15-2019 at 12:09pm
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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