I need a jet boat electrician for this question

[Jennkent5454]

here comes a complicated question-
I have a 1998 seadoo challenger 1800, It had and electrical short and I believe it shorted out the MPEM. I had a seadoo mechanic remove the original MPEM and replace it with 2 separate MPEMs from 1996 SPXs.
The jet boat runs fine. the 3 issues I have are as follows:
1. both of the tachs and the speedometer do not work. they have power because they light up, the mechanic says the were all three shorted out by the above mentioned electrical problem. is there a way to test the gauges? is there another gauge out there from another PWC that can be swapped out for these that is cheaper than the original?
2. the deck lights do not work, I dont think these run off/through the MPEM any how, what would be the easiest way to test these lights to see if they didn't get wired back correctly or at all?
3. with having two MPEMs now, he had to add another DESS & lanyard, which means there are now 2 DESS post. is there a way to wire both DESS posts into one ? and make it where any lanyard will work?

 

[Seadoobuddy]

Very interesting questions.
I like the idea of 2 MPEM in case one blows then you still have 1 motor to use.

Sorry but I don't know the answer to any of these. I'm sure the "big guns" will answer soon. I'll keep an eye on this thread.

 

[CaptSteve]

I will try to answer your questions as best I can.

1. The power for the gauge lights is separate from the power for the gauge itself. However, the power for the gauges are all common. The power to run the gauge comes from the MPEM itself. That is why the gauges do not have power without the dess being on. It may be that since you are using two different MPEM that the harness is not wired correctly. Also, the information for the Tachs comes from the MPEM and not directly from the engine like most boats do. If all your fuses are good, I would suspect a wiring problem in the harness itself. You would also have to wire one Tach to each MPEM separately. Of course, your mechanic could be right and the gauges are bad, but I do not think that a short could kill all the gauges. The reason I say this is that the speedo gets it's information from the paddle-wheel and not the MPEM. It only gets is power from the MPEM.

2. You are correct, the deck lights do not need the MPEM. However, since the fuse for the lights is in the MPEM, the power for the lights does use the harness that plugs into the MPEM. Again, I would suspect a wiring problem in the harness.

3. The DESS lanyard has a coded chip that is read by the MPEM when you attach it to the DESS post. Using the proper scanner, you can program any lanyard to any MPEM. I have never tried this, but I would think that if you coded the same lanyard to each MPEM, then you might be able to wire the two MPEM's off the same DESS post. Like I said, I have never done this, but theoretically, it should work. The only problem you may have is that the DESS post is also used to program the MPEM and to read error codes. If you have only one DESS post wired to two MPEM's, how would the MPEM know which one you were trying to program.

I would suggest you get a wiring schematic for the old MPEM and the new MPEM and see where you need to change the harness. This type of fix, is not plug and play.