97 Challenger 1800 Ignition to 1 engine

[D_dub527]

Recently purchased my boat and brought it on a week's vacation. Learning the hard way that these boats can't be jump started without major problems afterward. Upon getting the boat in the water, there was enough battery to start the starboard engine but the battery died while attempting to start the port side. We jumped it with a portable pack and got it started. As the week progressed, I had increasing issues with the port side engine not responding to the start switch. By the end of the week, I got no more beeps when I put the DESS key on, and now that I have it home only the starboard engine will respond to the start button.

What I've done:
1. Found the regulator/rectifier for the port engine was fried to charcoal, so I replaced it. Still no "beeps" or response from the port engine.
2. Jumped the solenoid for the port engine and was able to engage the port starter.
3. Replaced the port solenoid. Still no "beeps" or response. HOWEVER, I can still jump the solenoid and engage the port starter.

ALSO, if I connect the cable from the port engine to the post on the starboard solenoid I'm able to engage the starter with the starboard START button.

I have not yet:
1. Checked the speaker for the beeper.
2. Checked the switch for the port engine.

Trying to educate myself on electrical systems and how to check them with a meter.

I'm assuming I destroyed my MPEM and am seeing multiple threads and sources online that refer to converting to 2 GTX MPEMs.

Before I go down that route, does anyone have any words of wisdom? I'm completely new to owning a boat and am learning everything about electrical systems as fast as I can. Anything else I could be missing?

 

[brushmore]

Make sure you have a fully charged battery. I use a trickle charger always with the battery switch off. I'd check the beeper first.

You do have a copy of the shop manual, right?

 

[POPPS]

If you go in behind the gauges, perhaps you can try switching the leads to your start top buttons, this can help you diagnose a failing start stop switch. To test the beeper, unplug it, and run power directly from the battery to the beeper terminals, this will tell you if the beeper is failing. Be careful to not short your leads.

 

[alkiseadoo]

I just sent my Mpem to a guy named Nick at usedseadoompem.com as I had a similar problem and my tech told me he tested everyting else so it must be that. Has anyone else used him? Mine would allow one engine to start, then I started the other one and after about 5 seconds it would beep 4 times and shut them both down.