1994 vx225 bogs down on acceleration

[WhalerYamaha]

Have twin 1994 Yamaha VX225 engines. Boat runs great first thing in the morning. After engines get warm boat will not accelerate from idle. At approximately 1000 RPM engines turn off. Have replaced fuel bulb, low pressure pumps, fuel check valve and coils. Appears to be related to fuel accelerator pump (except no such device on this engine). Blinky-winky does not display error codes when engine is cold. Once you get past the dead spot (1000-1800) after multiple times engines run great up to 5500RPM. Any suggestions would be appreciated. Now leaning towards TPS but I hate keep throwing parts at the problem. Thanks in advance.

[rodbolt17]

can ya post a model number???
typically a Vx means a bass boat motor.
don't go by the decal on the hood.

[WhalerYamaha]

1994 225TXRS. Thanks in advance.

[rodbolt17]

see how much a model number makes.
you DONT have a VX motor just a stupid carbed 225 3.1L
carefully test the lift pumps, t.
that engine family eats them.

then do the carbs.
as a side note, you JUST stated no codes.
why the ffing ll would you now suspect the TPS????
I gotta know what led you to that thought.

the VX225 came into the US market about 1998 and was EFI.

[WhalerYamaha]

Rodbolt,

Thanks for the response. Probably lack of experience and desperation led me to thinking the TPS could be a problem.

1. I have only utilized the blinky winky with the engines cold, not after running them for a prolong period of time.
2. I wrongly surmised that if it was a carburetor problem the problem would be evident when the engines were cold or hot. It only happens when the engines are hot.
3. The fuel pumps are brand new and this is the second set of pumps. I firmly believe that it is not a problem with the fuel pumps at this time.

Maybe you can clear up how the carburetor work on this engine. I was under the impression that these carburetors do not have an accelerator pump. When one moves the throttle a signal is sent to a solenoid in the carburetor which increases the richness of the mixture. I had guessed that the signal to open up the solenoid was a direct result of the TPS. For this reason I was chasing a problem with the TPS.

Once again thanks for taking the time to reply.

[richie66]

fuel tank vent?

[rodbolt17]

when using the winky blinky remember it ONLY displays a code IF that code is active.
the engine ECU WONT store codes.

those carbs are fairly simple.
first make sure the electric pump tuns on and remains on at key on power.
it draws fuel from #6 carb bowl(lower stbd carb) to feed the six solinoids.
stuck open or missing T-stats can pop a piston.
that feed loop should have about 6PSI.

based on signals from the TPS,ECT and knock sensor these solinoids can alter A/F ratio up to 20%.

some models had a small tube hanging in front of the venturi, this is a high speed power nozzle that's only used past about 7/8ths throttle opening.

[jpdphoenix]

Same problem as WhalerYamaha

I have a 1996 S225 turu...on a cold start the engine runs great, no problems. But after running to a fishing spot and fishing for an hour plus on a hot day, the engine will start right up; but upon acceleration the engine will bog down and stall. Once I do get it started and get the rpms up it runs well. Then when I go back to idle it seems to run rough or maybe is missing. I was wondering from a past thread if anyone knew what whaleryamaha(1994 vx225 bogs down on acceleration) figured out? I have replaced the 3-side mounted fuel pumps and also the electric fuel pump. I have taken my boat to a dealer numerous times but they can't recreate the problem. I have run the boat on a portable tank with same problem.