That sounds like a fuel restriction between the tank and the engine. If the lines are more than a few years old the insides of them start to separate due to ethanol fuel and at higher rpm they will collapse and cause a restriction. Sometimes can be the ball that will go bad also but more often it is the line itself. Try hooking a small auxiliary fuel tank to the engine and go run it see if the problem persists.

@@diyboatrepair8005 makes total sense! What I also found in my investigation is that the electrical lines to the engine from the helm broke lose from the tie-downs under the deck and it started to hang very low almost touching the water. This weekend I shored up that line back to the decking and pontoon and got it out of the way of the water flow. We didn't have any problems after that. So it also looks like it was somehow "crimping" the line when the boat would hit higher rpms thus pushing the stern down lower into the water and possibly shorting out the signal?

My problem feels the same as yours

Jjj

@@diyboatrepair8005 if the bulb was bad the pump would suck it flat. if the ball isnt sealing properly with an electric fuel pump that wouldnt cause his issue most likely. but agree there is a restriction somewhere.

It could be the exhaust plug in the side of the engine holder is corroded out or it could be that the head has corrosion and is allowing water into the cylinders, both are not a terrible job to do and if you find that the exhaust plug is corroded out on the side, find a good local aluminum welder and have him grind down the plug and weld it shut with an aluminum plate. But you should change the oil and fire it up not hooked to water and rev it up real good for about ten or fifteen seconds and change the oil and repeat until you get clean oil and then do your diagnosing. I have seen water in the oil run fine for weeks and I have seen it ruin a motor in a day or two. So it seems you caught it at a good time!! Best of luck!

Hi Ben, In my experience I have known the fuel pump to fail completely instead of intermittently pump at a certain RPM, I would look towards having your injectors cleaned, as I have ran into that issue before and caused the exact same symptoms and you can usually have the injectors cleaned for about $100 at a local shop if you remove them yourself. Could also be a fuel restriction somewhere in the system but that would usually not be at a single rpm most times you would notice it in a more broad rpm range. Good luck!

@@diyboatrepair8005 Thank you very much for your reply. You are absolutely right.One of the problems I was very confused about was that the symptoms all appeared at high RPM, and once the symptoms appeared for the first time, they would also appear at low RPM.In order to verify this point, I did a verification today, and the driving speed was not higher than (3200 RPM) today, and I also drove for 3 rounds, without any symptoms of the previous.Is it a syringe problem or something else?Could you please send me an email? I made a short symptom video a few days ago, and I hope to send it to you to help me judge the problem, so that I can find the way to repair it. Thank you very much!

Pretty rare in my experience, I’ve yet to see one intermittently work, when they do go bad they just quit from what I have seen personally.

Did you ever figure out your problem?

@@that2doortahoe274 corrosion on cylinder head passing gasket had it welded and skimmed plus new gasket all good now no water in oil but on idle still a small amount of vibration may need advanced timing??

Sounds like a restriction in the fuel line somewhere, I would say maybe try a different fuel line and primer ball from tank to engine and see if the problem continues.

Thanks. Found the problem. It was a fuel filter.