97 200 Vindicator runs good up to 4K stumbles after

[Fenix009]

I have a 97 200HP Vindicator on my 290 Stratos.
It starts and idles great and pulls the boat, 4 passengers, german Shepard and a rider on a tube up to 35mph at under 4K rpm. Last year when I bought it it ran mid 50’s at about 5k with two adults and two teens in the boat. Last trip out it would act like it was fuel starved at 5k. Mechanic found the fuel bulb was collapsing and replace fuel lines from tank to motor including the bulb.

This year it it runs great when we keep it under 4000-4200 rpm range. Above that it starts to stumble like is fuel starved. RPM bouncing from say 5k back down to 4K. If I punch it it is worse than if I ease into it. If I slowly inch up it will go to 4500 before it starts, always bouncing back and forth the 4K. Also once it’s warm it takes 2-4 hits of the starter to start.

Any ideas on what to check next?

 

[Joe Reeves]

You might want to speak to your mechanic to have him versed on the functions of the Anti Siphon valve assembly fitting at the main fuel tank, as follows:
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(Fuel Anti Siphon Valve)
(J. Reeves)

Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vacuum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.

NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.

The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures the problem.

The above procedure will cure a restriction problem with the anti siphon valve as stated. BUT, it may also allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.

NOTE: There has been cases when the output valve in the fuel primer bulb would come apart, and the inner portion of the valve would actually reverse itself and be drawn back into the primer bulb's output valve body. This in effect would create a shut off valve and result in a fuel restriction. If this is the case, you should be able to feel something laying in the bottom of the primer bulb when held horizontally.

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