Sportster 5A MPEM fuse

[95sportster]

Was out cruising the lake a full throttle and all of a sudden the boat just died. After troubleshooting, it was the 5A fuse. I replaced it and it burns out immediately. After further investigation I found out that my 2 engine ground cables had broken loose, probably from a combination of being 17 years old and me jumping waves. A test light confirmed that one side of the fuse slot is getting power from the battery and the other side of the fuse slot is grounded which leads me to believe the diode is shorted out.

I just wanted to ask if the bad engine ground could have caused this or if there is another issue that I should be chasing before replacing/repairing the MPEM.

This is a 1995 Sportster.

 

[Dr Honda]

Sounds like the classic diode short. It's normally only caused from jump starting the boat... but since it's part of the charging circuit... a short (or open) on a power cable can cause an issue.

So... if you were at full throttle... and the ground cable came off... you could get a voltage spike from the regulator, and kill the diode.

If you are brave... cut open the MPEM, and change it.

 

[95sportster]

Sounds like the classic diode short. It's normally only caused from jump starting the boat... but since it's part of the charging circuit... a short (or open) on a power cable can cause an issue.

So... if you were at full throttle... and the ground cable came off... you could get a voltage spike from the regulator, and kill the diode.

If you are brave... cut open the MPEM, and change it.

OK great. Ill start by replacing the ground cables. As for the diode: I've been searching on the forum and everywhere else for the last few hours to find out all I can to do the repair myself. I couldn't find much on the sportster itself but lots of pwc guys have done it with success. Their threads seem to call for a Motorola MR2535L diode. Is this the right one for my mpem? And I also could not find a picture of where exactly the diode is located on the sportster mpem.

 

[95sportster]

Just looking for confirmation that the diode in the above post is correct for my mpem. Also wanted to see if anyone had a pic of where exactly it is located on the mpem under the rubbery compound.

 

[95sportster]

No one else has attempted to repair their sportster mpem themselves???

 

[Dr Honda]

I've done it on Ski MPEM's... but not in a boat. So... I have no idea where it's at on that MPEM.

That diode should be fine.

 

[95sportster]

I found the diode. Tested it on a multimeter and showed very little resistance in either direction. I have the replacement in the mail.

 

[95sportster]

Just to provide closure to this thread. I made up some new ground cables with new cable and lugs. I soldered in a new diode on the MPEM, tested the unit on a multimeter and it showed resistance in one direction as expected. I finally got the unit in the boat this afternoon and she fired right up.

Thank you Tony and the others that I PMed to get this done. You guys are a lifesaver.

 

[speedster98]

Could you post a pic or description of where the diode is located on your mpem?

 

[95sportster]

I do have a pic with my phone but its not very clear. Here is another thread started by someone else that did the same fix with a speedster MPEM and he put up a picture. The diode on the sportster MPEM was located in the same spot- between the 5A and 15A fuses.
http://www.seadooforum.com/showthread.php?48403-Problems-with-the-mpem-on-a-1995-speedster!