'94 3200scr 5.7merc/Bravo2, port engine overcharging

[geoffm70]

Nice I had a couple weeks of normal use/no issues, just enjoyment. Then...

I replaced the frame around the port trim motor, the original had totally rusted away. The next day, went for an hour run around 3600rpm and my chart plotter had an alarm and displayed 17 volts warning and shut down. The dash gauge had jumped from 14v to max (stops at 16V). Figured it was the voltage regulator, already replaced the alternator on the other engine, so got a new one for this Port engine. After replacement and during seatrial, gauge was showing 14V and all was going good, hit a wake wave and saw the volts jump to over 16 again.

Must be a lose connection somewhere right? I suspect the macerator pump which sometimes won't come on, and then does. Or the new stainless frame for the trim and all it's wiring?!? Oh, and the batteries are less than a year old and seem fine.

[mmwjr]

Could you have a wire terminal to close the the trim pump frame or damaged wire insulation?

[geoffm70]

took the wires off the old frame and attached exactly the same way on the new stainless steel frame. all connections are clean and tight. maybe stainless is bad for grounding?

[mmwjr]

I suspect there’s something else causing the regulation issue. I would verify the wires on the alternator are correct and tight. Was any new electrical items added recently?

[geoffm70]

So had a bad connection on the fuse panel with the Macerator pump. fixed, no more overcharging!

[shrew]

How is the macerator pump involved here?

[geoffm70]

Well you're right of course, the pump has nothing to do with it. I thought the loose connection at the fuse box was the culprit, and all was fine for about 90min cruising a 3600rpm the volts stayed between 13 and 14. Then we hit a current (abt 12-14 knots) through a narrow channel (Dodd Narrows) and pop, volts jumped to 16.4 to 17. Got through the channel and out of the worst current and shut that engine, but not before smelling electrical smoke. Managed to limp home on the other engine. WTF! Brand new alternator on that engine, waste of money/time. Now I'm back to suspecting the Stainless Trim Pump frame again, this all started when I changed that.

[mmwjr]

Unless you have created a short when changing the pump bracket I don’t think it’s the culprit. Key here is the voltage output changes when the boat is subject to rough water. Try swapping the two alternators to see if it follows an alternator or stays with the one engine. You can also try disconnecting power from the trim pump to remove it from the equation.

[geoffm70]

Agreed, doubt it's the frame. Excellent suggestions, thanks. Going to try this tonight or tomorrow morning

[shrew]

You could simply have a bad regulator on that alternator. It happens.