OMC 5.7 Ignition prob linked to trim button

[Grundei]

1992 OMC 5.7 LIter - Starts fine, idles fine - when accelerating -horrible misfiring - no power - often kills (Carb has been rebuilt) - Problem either goes away or gets a lot better if I hit the trim button (Up or down - makes no difference). I assume that by hitting trim button I am somehow altering the electrical system. Any ideas on how hitting trim button could influence acceleration? (To be clear - it is not the change in trim that is involved - it is merely activating the trim for an instant.) Other symptom is when going at full throttle it will start to die - again hitting the trim button instantly causes it to resume at full speed.

Help! (Thanks)

 

[Boatin Bob]

Re: OMC 5.7 Ignition prob linked to trim button

Sounds like you have a bad connection somewhere. I would start off by removing, cleaning all battery cable conenctions at each end and making sure they are really tight.

 

[Grundei]

Re: OMC 5.7 Ignition prob linked to trim button

Thanks Bob - found it this morning - where the ground in the main wiring harness connects to engine - it was loose - so I guess pushing trim increased the strength of the ground.

 

[Grundei]

Re: OMC 5.7 Ignition prob linked to trim button

Well I thought I had found the problem - but no so. All grounds tightened - and additionally set up temporary ground using good jumper cable. Trim button still influences running. Next move - unhook trim power cables from battery and hook up to second battery. - No change - hitting trim button still changes running. Even tried totally unhooking power to trim (hooked to no battery) - same result - Any theories?? I suppose I could run a new wire(s) to the trim button - thereby removing it from wiring harness?? My mechanic thinks he remembers a service bulletin regarding interaction of trim button and ignition but can not locate it - and has talked to OMC factory support who also did not seem to have it.

thanks

 

[Boatin Bob]

Re: OMC 5.7 Ignition prob linked to trim button

At the back of the engine right the 50 amp fuses is a big (10 pin I think) black round canon connector usually held together with a SS hose clamp. I would take that apart and check for any corrosion going on in there. It still sounds to me like you are missing or have a bad ground somewhere.

 

[Grundei]

Re: OMC 5.7 Ignition prob linked to trim button

We thought that the connector that you mentioned was the problem so we cut it out and hardwired all wires - no change. My mechanic thinks he remembers a service bulletin with trim button involved - but no one at OMC remembers it. Any idea where there might be a complete set of OMC service bulletins? ANy other suggestons? (THANKS!)

 

[chiefalen]

Re: OMC 5.7 Ignition prob linked to trim button

You could try running a wire with a switch at the helm from the battery to the coil.

Turn on the switch and crank and start the motor, leave the switch on and run the boat.

Has the problem gone away, with the jumper wire installed?

If yes maybe the solenoid going bad.

 

[Grundei]

Re: OMC 5.7 Ignition prob linked to trim button

It appears that the problem was in the alternator - intermittent situation - hitting the trim button must have triggered different voltage. Thanks for all of the ideas.