Issue with 1997 seadoo challenger 787

[Seanjohn204]

Hello everyone this is my first post on this forum, ive had many issues with my old seadoo challenger but was able to research here and resolve the issues. the issue im currently having with my 97 challenger is a bit complex. ill start with a bit of back round with this boat. Its a 1997 seadoo challenger with single 787 motor. I purchased this boat from out of town knowing it had issues running. When the boat is started it will not run past 3000 rpm, and it backfires alot. Previous owner had the MPEM replaced with a GTX MPEM (now i dont know if there is a conversion kit, most likely hillbilly install), same issue persist. I received the boat like this, i have not put it in the water yet as i figured it would be a waste of time. Currently its sitting waiting on a replacement MPEM to test(having a hard time sourcing new mpem, i still have the original MPEM that came off).

Compression, valve timing, ignition, plugs, and crank shaft have all been checked and are in good condition. It starts great, but also starts in drive and reverse. I havent been able to locate a replacement MPEM, however i found a company that is able to take my MPEM and wire up a conversion kit, the cost for this service is $1000USD. Before i spend this kind of money i want to make sure i exhaust all my options. So my question is am i on the right track with testing the MPEM? also any other suggestions.

 

[Sandman251]

It's your neutral safety switch. The boat currently thinks its in neutral, that's why you are able to start it while the shifter is in "F" and "R". Another function of the neutral switch is to limit RPM's to around 3000 when the boat is in neutral. Easy and cheap fix. The switch should be located on the shift mech and be easy to replace. As far as your backfire goes, I would always look at timing first. If compression, timing, ignition, plugs, and crank shaft are all correct and functioning, I will defer to somebody else with more expertise. A lot of people point to the MPEM first in diagnosing run/start issues. Its almost always something else. I might try to re-install the old MPEM unless you are certain its cooked. Hillbilly attempts at re-wiring almost never work.

 

[racerxxx]

If they did replace the MPEM with one from a gtx that would rule the neutral safety switch out, they didn't have a neutral safety switch to the best of my knowledge. So, when you start it and rev it up, are you in forward on the lever? If you're in neutral you'll get what you're experiencing. If it does work then that would mean they didn't change the MPEM. And if it still didn't work, you can jump the switch to make continuity AFTER you start it and then see if it will rev up higher than 3300 rpm.