OMC 350 loses power with electrical equipment activation

[f18drivr]

Hello,

This is my first post, though I've gotten a ton of repair advice from this forum.

I have a 1988 OMC 5.7. I have had a ton of problems with this motor, but they have mostly been sorted out. This one baffles me.

At high RPM, when any electrical equipment is activated, the motor hiccups. The worst offender is the trim motor, she'll be running at 3800rpm and I'll adjust the rpm.... blah, she'll bog down to 2800 immediately. I haven't tried holding the trim continuously to see if she'll die, but there is a significant lose of power immediately upon activation.

I tested the other electrical equipment to see if they would do the same. I have separate trim tabs, when I use them, the bilge or the blower motor they cause a very small hiccup, the lights and horn do not.

I am taking the battery out tomorrow to test it, it seems a little weak, but not terrible. I was thinking stator or alternator? Feels like a short somewhere, but I don't even know where to start with this one.

Thanks,

Tony

 

[f18drivr]

Re: OMC 350 loses power with electrical equipment activation

To clarify, when the trim button is released, power comes back immediately.

 

[nitwhit]

Re: OMC 350 loses power with electrical equipment activation

Could be a bad battery but it sounds like a bad/weak alternator to me. Pull it and have it tested. If it's bad, make sure you replace it with a marine model. You might also check your battery cables and grounds to make sure they are clean and secure.

 

[bruceb58]

Re: OMC 350 loses power with electrical equipment activation

You have a resistive connection somewhere so you are getting a voltage drop when you activate anything with a high current draw. Check your connections at the battery especially the lead that eventually goes through the fusible link to the main engine harness.

Same thing happened to me the beginning of last year. I took all the connection off at the starter where the battery cable connects and sanded everything to shiny copper and reinstalled and never had the problem after that.

 

[f18drivr]

Re: OMC 350 loses power with electrical equipment activation

This forum rocks!

So today was the day, I cleaned every connector I could find. Quite a few of them were pretty nasty. I pulled the battery and had it tested, good. I had the local autozone test the alternator... BINGO!

I am looking online for a new alternator to avoid the $170.00 marine model that autozone can order.

Long story short, you guys rock. Thanks.

 

[nitwhit]

Re: OMC 350 loses power with electrical equipment activation

Glad you found your problem. To bad it was not the cheap solution but that's the way it always seems to be. Google db electrical as they sell most marine alternators for less than $100. For a quicker and cheaper solution than going through your local parts place, if your old one is a marine version, take it to a starter/alternator shop and have them rebuild it. Should have it back in a day that way.