OMC tilt problems, shorting out when trimming up or down

I have 1986 Chaparrall, it has the omc 5.0 in it. Sometimes, not all the time, when I use my trim swithc (up or down), it shorts out badly while I am on the gas. It never does it when the engine is shut off, it all seems to operate just fine with the engine off. It seems to only be an issue when the engine is running and is intermittent then. Most of the time it goes great, and sometimes when you hit the trim button it goes crazy. I have ruled out the switch on the control handle. Seems like maybe when the motor has ran for a while or when the gas gauge gets to around 1/2 or especially when it get lower.

Any help is great, if you or someone you know has had this problem and has gotten it fixed and you could let me know what they did, that would be outstanding...

Chris

sounds like your relay contacts may be sticking.

What have you been doing to get the trim motor to stop? disconnecting the battery?

I dont do anything, its only when i push the trim switch on the control lever. It is really intermittant. Where are the relays located?

Usually i put the boat in the water and everytbing is fine, i am usually on the ohio river, after a while of boating and i usually dont have to be cruising the whole time. Say at around about half a tank or so, when the water gets a bit rough and i try and trim down or up it acts like something is shorting out. As soon as i let off the switch all is well avain. I have read where a possibilty could be the relays but i am not sure where to look for them.

Any help is greatly appreciated

when current takes a short circuit path through a switch, the electrical device it powers continues to operate when the switch is released
so when you said "acts like something is shorting out" I was assuming the trim motor was staying on.

rather than try to put technical terms to it.....

I'm going to guess that what you mean , is the boat loses power when you use the trim switch....as in the engine slows briefly, and rpms drop

That's a common symptom of generally poor electrical connections on a boat.

The trim motor draws very high amperage, more than any other electrical accessory, so if your battery cables or terminal connections are less than stellar, it can cause the entire system voltage on the boat to drop.
When that happens, you no longer have enough system voltage for the ignition system to make proper spark for the spark plugs. (or, for any other electrical component to work properly)

Start at the battery. clean all terminals with a battery terminal and post cleaner brush. While the battery is disconnected, remove cable ends from starter and engine block ground connection - file the terminals shiny and file the terminal side of the nut shiny and reassemble - do the same process at batt if batt has wing nut type posts.
If you're energetic - you can look at alternator connections too - and your boat probabaly has two 50A barrel fuses (black cylindrical plastic housings) -those fuse holders like to rust inside. steel wool cleans the fuses (car stereo shops have replacements).

Connect the battery, and if your batt has wing nuts, use a pair of channel locks to tighten them more than finger tight.

If you have a battery switch and multiple batteries, you have several more connections to maintain. I'm not a fan of those high current A/B/Both switches. They can cause a lot of voltage drop problems.

Thanks for the info hystat, I am headed out of town to Cleveland today and will be back Friday morning. We plan to go listen to a concert on the river Friday night so I will get on this asap when I return Friday afternoon. It doesnt keep from using the boat just makes it a bit unpleasent when it starts. I usually end up bumping the trim switch to get the outdrive to go up or down as needed. This can be a pain if the water gets rough in a hurry, and it is annoying when things dont work correctly. I am also getting ready to start wet sanding and buffing the boat, one side is a little more oxidized than the other but trying to get the thing looking and working great.

Thanks for your input and I will let you know how things go when I return and get to mess with it. Thanks

Chris

1986 should be a Cobra drive.... just realized you say tilt in title and trim in text, so it's a Cobra, correct? hydraulic tilt/trim rams on drive...

Yes sir. It is an OMC 5.0 (chevy motor), and yes it has hydraulic trim cylinders on it. I am hoping there may be something more definitive on your brain??? lol I understand wires and checking my connections, but there is an awful lot to go thru. We just got the boat at the end of last year and this year is really our first year for a used boat, all others have been somewhat new/newer. So there is a few things I am learning about this particular boat.

25 year old connections in a damp bilge.... probably about 20 years overdue for maintenance... cleaning up wiring and terminals is something you want to do every few years on a boat

I still don't know what a boat acts like when it has a dead short or whatever... maybe take another run at the symptoms and chief or someone will have a better idea

"going all crazy" or whatever you said doesn't help us help you.. lol... hope you get it sorted