Another dreaded 5A fuse on the MPEM

[theomajigga]

Hey guys, I'll give a very quick background story!

Bought a 96 sportster in "not running condition" for 1k. Sat in storage for 2 years... I rebuilt both carbs, thing ran perfectly. Saw a 96 speedster for sale on craigslist, with a second 85% complete boat included. Offered up my running sportster for his speedster that had the 5A fuse problem...

I am very electrically inclined, and as such I have already ordered the diode that gets burnt when it gets jump started.

Here is my question: I was under the impression that it was an instant kill on the fuse when this diode was bad. When a new fuse is put in, I can get both motors to start and run for a few sec (out of water and don't want to push it) and it doesn't kill the fuse. Does this still sound like the diode? Should I start elsewhere? stator? Rectifier?

Thanks in Advance!!

 

[Andy4k6]

Doesn't sound like the diode, when the diode fails it goes directly short to earth, I have never known one go intermittent.

 

[theomajigga]

Ok. So a bit of an update, and I'm going to start probing it... But it only does it when it's throttled up with both motors, when they are both idling, it is not problem, but I'm going to drop it in the water and see if it is taking on some water and shorting something out.

I should check the stator and the rectifiers???

 

[ialonso]

Rectifier easiest to check. Do you have a volt gauge/meter on the system to see what the voltage looks like when it pops?

 

[theomajigga]

Not yet, one is on order that will be hard wired into the "cluster"

But, here's another update. I took it out on the water myself, as this was the POs diag (MPEM failure). It ran fine. I'm super confused.

I have some cavitation that I need to look into, but ran great, putted around on starboard, no fuse pop, putted around on port, again no fuse pop. Putted around with both, no pop. Gave her a bit of hell, and off she went. Ran fine. I'm nervous to go out on the river with it, but at least I feel a little more confident. ON TO CAVITATION.