Help, 225 Optimax accelerates when trimming

[flo-k-munkers]

I have a 2002 225 Optimax ser. # 0T471031, model # 1225D83ZY on a 22' ACB Waverunner. My smartcraft alarm system is showing a "fault sensor" alarm. As an added bonus when I have the motor idling in gear and hit the outboard trim button I get a surge of acceleration for as long as I touch the button. Trimming does not affect rpms unless at idle and in gear. The engine will also do momentary surges of power at random intervals when in gear and at idle without any participation on my part.

I have changed the TPI with no effect, and disconnected the compressor temp. sensor with no effect. If I disconnect the air temp sensor or the map sensor I do not get the acceleration when using the trim button however I still show a fault sensor alarm. I replaced the air temp sensor with a new one and still have the problem.

This thing is driving me crazy!!! I am on Kodiak Island without a Mercury dealer on the Island. Any help is appreciated.

[EuropeanAM]

I'd start by checking your battery connections, to confirm that they are CLEAN AND TIGHT. Stack the terminals "engine cable first, then remaining ones largest to smallest". Finish off connections with a stainless locknut.

Also, ensure your battery is a MINIMUM of 1000 MCA or 800 CCA. More is DEFINITELY better... especially if you like to run graphs/pumps while you're fishing.

For a list of good batteries, see the post pinned to the top of this forum.

[flo-k-munkers]

Thanks for the suggestions. Appropriate batteries, clean tight terminals. I have found one of the problems based on the iformation you had provided in an earlier post. The fuel gauge sending unit had a ground. Removing the ground has stopped the unwanted acceleration. Hopefully it hasn't damaged the ECU. Engine seems to run fine on a hose.

I am still showing a "fault sensor" alarm on the smartcraft and have been unable to determine which sensor is faulty. I don't know if there are tests I can perform without a diagnostic tool.

I will be contacting you to order a sensor if I am able to determine which one it is. Thanks for your advice.............John Sullivan

[EuropeanAM]

Good find on the fuel sensor! Haven't heard of it causing accelerations when trim is operated, but it's certainly possible (since it's known for causing PCM issues).

I'd recommend a computer diagnostic be performed- try to obtain a printout of the Freeze Frame Fault History- and of course, I'd be glad to take a look at the printout if you'd like.