454FI stumbling?

[cc23]

Hi guys. First post and i need some help, my 1994 2000 tige has the fuel injected 454 and stumbles when we idle for a while. It only does it when its hot. I know something is triping something into making it run rich, but what? I have noticed the temp Gauge reads a little warmer when this happens but i dont know if this is maybe the cause or a result of the problem? The boat will clear itself out after a couple minutes and runs great everywhere else. Thanks for any help.
Jason

[boatwakes]

Can you get me a serial number? Overfueling is usually caused by the coolant temp sensor malfunctioning and reading outside actual temp but can also be a bad fuel pressure regulator or fuel pump.

[cc23]

Engine # of224424 454 mavnum efi ski. Thanks.

[chpthril]

A lean running engine can run warmer then normal and a rich running engine can run cooler. Also, the temp gauge receives its signal from a temp sender and the ECM receives its signal from a CTS (coolant temp sensor), so a slight change in engine temp when the problem occures, could just be indirectly related.

I would pull the vacuum hose off the regulator and look for the presents of fuel

[boatwakes]

CTS mercruiser part number is 805218T $25. There is also a STRONG possibility you have a stuck injector. To test this, get a fuel injection pressure tester from Kragen auto and connect to the fuel rail at the front of the motor. It will have a schrader valve (think bike tire) that you screw the tester into. When you turn the key to the on position, your fuel pump will cycle for 2 seconds then shut off. The fuel pressure should be between 28-32 psi and not fall below 20 psi for at least 15 seconds. If it just drops right off you've got at least one stuck injector. If those tests turn out fine, start the engine and watch the fuel pressure to determine if it's over or under pressurizing due to a faulty fuel pressure regulator. Let us know the results.

[cc23]

Thank you so much for everyone's help. I got a new cts installed tonight and cant test until tommarrow as i am taking the boat on vacation. I will try and pick up a pressure regulater on my wayout of town. Also the problem doesnt happen until the boat gets to about 170-180 degrees. Just idling wont do it. I have to be towing or running it hard and then idle around for a minute or so for it to act up. It normally runs cooler then that at idle or alower speeds