351W will not rev past 4000rpm - ideas?

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?

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.

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

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

link

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.

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.

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.

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.

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

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.

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,

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.