Very frustrating electrical issues with 85 gran sport.

[Grand Sport Guy]

Where to start. This season I've been having some intermittent electrical issues. 1st issue I had was the port side motor not starting. So what happens is I turn the key to start and the gauges don't do anything . What I also notice is the switches on the instrument panel don't work at this time.I will note that the blowers, both bilge pump and the starboard wiper work.. Checked connections I couldn't find anything out of the ordinary. I threw a meter on the fuse for port ignition and I have my 12v. I check the back of the ignition switch and I have 12v. Then I turn ignition key on to start and I loose my 12v. I disconnect the 3 purple wires and I get my 12v back. Now I know my gauges weren't working so I traced the one purple wire that fed the gauges and disconnect it, but hooked the other 2 purple wires back up. Boat would start and run . Then after a while the boat started doing the same thing all over again with the gauges disconnected. So I checked the dash switches for a short to ground. I see about 50 ohms. So I disconnected all the switches one at a time to see if I can isolate it. Nope couldn't find it. So then I checked all my grounds on that motor from the battery to the starter. It didn't fix the issue. I'm trying to find a wire diagram for the ignition. I'm not sure if this boat has a starter relay other than what's on the starter. Also I believe I have 2 issues here. I will also add that if I let the boat sit for a few hours it starts and acts fine. The switches on the dash even work. But whenever the port motor doesn't start the switches don't work either. Something ties them together. Very frustrated ! Oh, there's brand new battery on that motor also.

[Billm]

You have corrosion issues that come and go as you are fiddling around with the wires. I would definetely start by replacing the ignition switch. It is not very expensive. If you have enough slack, get rid of the push on connectors (QC) and use ring terminals. I would also upgrade the fuse blocks, too. I replaced all my fuse blocks with new Cole Hersee fuse blocks. There wasn’t enough slack in the wiring harness to use the Blue Seas ones. I used a separate bus bar to connect all the grounds to. If they are the original fuse blocks from 1985 with glass tubular fuses, they will likely be plenty of corrosion there. As a temporary fix, run a jumper wire with in line fuse from the fuse block feed directly to the ignition switch. Do the starboard side as preventive maintenance.

My inboards have slave starter relays mounted on the engines near the coil. Mine do cause a lot of problems. Usually slow cranking.

[Grand Sport Guy]

1st thing I did was replace the ignition switch and I also replaced the fuse panels.

[Billm]

On my boat:
The port ignition feeds of the starboard fuse block and visa versa.
The ignition switch “on” position energizes the engine, dash gauges and hour meter. These should be active whenever the switch is on. Everything else comes directly off fuse block. Some of my dash switches like the horn come off the same fuse block as the starboard engine. Does that always work?

I don’t think you have a short in the dash switches, because wouldn’t that blow fuses? I still think something is funky with the ignition switch. Make sure all wiring harness plugs are tight. Beyond that I can’t think of anything else.

[Grand Sport Guy]

So I figured out my issue a few weekends ago. It ended up being the main overload for the motor. It would start when cold but after it warmed up it would build enough resistance and caused the overload to act like it was open. I replaced the overload and haven't had an issue since.

[Billm]

Thank you for posting the solution to your problem. I am not familiar with the main overload. Where is it located?

[Grand Sport Guy]

It's located directly under the heat exchanger. Red button with 50a printed on it.. Very difficult to get to. This is why I relocated it. Lol