Issues after replacing the carb

[Mastercraft81SnS]

Hi all,

 

I'm hoping someone can help me out on here. I installed a new carb last season and have been having issues with it. Long story short the boat had a car carb on it so I put a brand new boat carb on.

 

The issues only happens when I'm about to go skiing. The driver hits the gas and the boat stalls and won't re-start right away. We put the boat back on the lift and let it sit for a day. I get the boat out and do a lake test I try all kinds of things it runs great. I lake test is a few more times then try skiing again then it acts up again. I repeated this process multiple times and try different things. It has spark after it acts up so I'm thinking it's fuel related.

 

The boat runs good at all RPMs it doesn't seem to be running ritch or lean. I take off hard out of the hole and drive the crap out of it. I can drive around for hours at idle no issues. I'm stumped on this issue.

 

The boat is a 1981 Mastercraft with a 351w in it.

[jsully]

Couple years back my 351w had a similar issue. For me it was clogged up fuel filters. Mine has the large screw on fuel filter that looks similar to an oil filter, as well as a smaller fuel filter in the reservoir of the fuel pump. Replacing both cleared up my issue.

[BraceMaker]

Maybe someone took the boat wakeboarding and now it doesn't like skiers?

 

I think what I would do is after you get it to stall try to trouble shoot the fuel status. Pop the spark arrestor give it a quick toot if ether and see if it fires. Pull out the silver knob and go to full throttle in reverse twice then try to fire it (accelerator pump will squirt silver doo hickey blocks forwards throttle to about 1/2 but let's you go full backwards.

 

I suspect your floats are set wrong. The engine sits on a angle to the rear. Then a skier goes and stands in the platform dorking with their gear and boots and gloves and soap. Then the boat is sitting at a more rearwards angle and the float level is further off. Either overfilling or maybe draining the front bowl to the rear bowl and you punch it there's no fuel for the accelerator pump and the power valve opens to enrich and you stall. Then being fuel level is off it doesnt want to start.

 

Back on the lift sitting more level and the float issue resolves.

 

To troubleshoot have a few people sit on the back and see if that duplicates your issue.

 

 

[LOTW]

Find your local old school hot rod engine builder, take it to him or whomever he recommends and have them give it the once over. These guys are getting far and few. Boats usually have different carbs than cars etc.

[Keukaskier]

Adjust accelerator pump screw?

[BraceMaker]

@LOTW boats need marine carbs but the difference vs a automotive is all in safety features like J tubes.

 

Same basic set up

[MDB1056]

If this only started after replacing the carb and no prior instances then it's obviously fuel delivery related and not spark. Unfortunately new carbs are not always set up properly. I lean towards replacing all filters if replacing major item like the carb. Give it a clean new flow. But also as noted above it could be a set up item like float level etc. Not sure from your post if it starts cold fine every time and it's just when you go to hit it that it dies? If it always starts cold fine always that narrows the search. Whatever it is it's an easy fix once found. Carb boats are simple.

[wski1831]

Check if it’s getting fuel when it doesn’t start. You can pull or loosen fuel lines and see if or how much comes out and where the blockage is. If you haven’t replaced the filters mentioned you should.

I had a friend that replaced his fuel pump with an aftermarket one. His fuel line ended up just long enough to reach or so he thought. It pinched where it went under the fuel tank and restricted the flow. It ran fine but not with a load. Good luck.

 

 

[2Valve]

pull the spark arrestor and verify that the carb squirts a strong stream of fuel when the throttle is opened. I just rebuilt a Holley with the same symptoms you have and it was the accelerator pump.

[jepski]

Good news is you have three variables: Fuel, Air, Spark so you can rule out a $5000 LCD display causing a problem LOL. Crazy as this may sound..b/c all signs point to the carb and fuel...it could be ignition related. Coils can start to fail and present this failure when hot. Follow @2Valve suggestion above. With engine warm so choke is open but engine off have a buddy quickly more the throttle wide open. You should see and hear fuel spewing into the carb. If you do confirm the pump is supplying fuel, I would look at the coil and other ignition components. Not sure if you're running points or EI module, and original distributor. I blamed my carb for poor hole shots last year (it's only 2 yrs old) and after checking the timing I was not getting full advance b/c of a broken spring in the distributor. Spent money on a new Pertonrix distributor and WOW, like a new boat.

[GPJ]

Friend had similar issues last year on same boat. Rebuilt carb didn't fix it. Was fuel pump diaphragm.

[DW]

When you lake test the boat are you doing exactly what your driver does when the problem occurs, and I mean exactly. Have you had him drive it with you observing the problem from in the boat?

Fuel pump, accelerator pump & float level are probable culprits. Is the new carb set up exactly like the old one? Jets, pumps, metering rods, discharge nozzles, float levels, manifold wedge, etc?

[Rednucleus]

Why did you change from the original carb - is it having the same problem with this new carb as well?

[LeonL]

I can only assume that this is a Holley. Not many of anything else. No metering rods as someone suggested checking. My bet is float level and/or accelerator pump. Accelerator pump is easy check. When it fails, just remove the spark arrestor and manually activate the pump lever and see if you get a good squirt from the nozzles located in the center of the carb. There is a cam that is adjustable that may need to change. There are two screw holes on the side of the arm. This allows different positioning of the cam.

[Mastercraft81SnS]

The boat is still buried in the barn so when I get to I'll post what the problem was. As soon as I saw someone say check the float level it dawned on me that I never check that. I did a tune up on it and changered the filberts and plugs last year because I was just stupped.

 

The boat starts right up and runs great other then when I'm trying to go skiing. With me just in the boat on my lake test I couldn't re-create the issue. The carb is set up just like the old one. The old card was a car carb the problem with it was it was running rich. Instead of messing with it I went out and bought a boat carb for it the 600cfm holly.

 

My plan is to check the float level and the accelerator pump like suggested above.

 

I asked about it on another page and they suggested that I replace a bunch of random parts such as the alternator, starter, distributor, and basically every part you can takeoff with a wrench. I guess I should have asked here first. Thanks a lot.

[Wayne]

@Mastercraft81SnS can you list the model or part number for the carb you bought?

 

You mentioned it has spark after the engine stall. Did you pull a plug to check spark or just do the screwdriver in the plug wire trick? If you pull the plug, was it fuel soaked, have a lot of deposits on it or was it white?

 

I’m trying to determine if you have a stall from an over rich or an over lean condition. The other thing I’m trying to figure out is if you have the right carb for that engine. Even though it’s a 600 CFM carb it may be set up for something different than a 351. The mode number or part number will tell me everything about that carb (jets, power valve, metering block, accelerator pump cam and so on).

[Jody_Seal]

Probably not carb problem. 40 year old boat. Original key switch? Original wiring? Original fuel pump? Original fuel hoses? Anti siphon valve? Original neutral safety switch? Shoot i could go on forever.

[Zman]

About a year ago, in my ski bud's 89 Ski Brendella we found 2 of the problems @Jody_Seal mentioned. The inner liner of the 30+ years old fuel line would collapse when accelerating hard. Lucky we found this as the line was also brittle and would have soon cracked. The bigger restriction ended up being crud in the Anti-Siphon valve on top of the gas tank.

 

[Mastercraft81SnS]

@Wayne I think my carb is a Holley part number 0-80319-1 from my reach it said that was the right one. Am I wrong?

 

I used a inline spark tester.

 

I'm planning on working on the boat this week when I get it in the water. I did do a fuel pressure test and I only have 4 psi at idle. I was thinking I should have mor around 6-8psi?

 

 

 

[ReallyGottaSki]

4 is good, 6-8 overcomes the needle/seat and floods out

[Lowballer]

It should be a 4160. Go to the Holley website and tune it with a vacuum gauge per the Holley manual. If it won’t tune check for vacuum leaks. If there are no vacuum leaks check compression in all cylinders

[Mastercraft81SnS]

I finally had time to work on the boat and get it in the water this year. It really had me scratching my head on this issue. As I said I put the new carb on at the end of the season last year and I only had time to try it once. It has been driving me nuts all winter!! I end up taking the jets and power value out of the old carb and now it's fixed.

[LeonL]

What are the jet sizes of the old and new? Power valve numbers? Just curious. Glad it's running right!