HELP! 99 GTX Dies down from full RPM

[GlglennGTX]

I seem to have had one thing after another. Last year I put a rebuilt engine into seadoo. No problems for a while. This year I replaced starter and exhaust pipe gasket (damaged from previous repairs). When I took it out to test it ran great. I spent a while running at various RPM. Then I tried full speed. Wide open gets around 53 mph, a little less than the original engine. It was running excellent and then bogged down to nothing, dead. I finally got it started back and it ran rough for a couple mins then got my power back. High RPM for extended time, running strong, suddenly bogs down dead. Changed plugs got started again same thing. Any possibility water getting in engine at high RPM only??? Also the same evening frustrated too much to be working on seadoo I charged battery and hooked up backwards. Now key doesn't work. What did I fry? No smoke or crazy sparking occurred maybe just a fuse? If so where? Thank you very much.

 

[timmyboy76]

check the all fuses around the mpem. Did same thing with my boat, but smoked from mag assy, maybe starter, but it smoked.
I'd lean more to carbs need some lov'n, and if that don't work, disconnect the red wire from rectifier...

 

[GlglennGTX]

Further questions

I guess I should be dealing with only one problem at a time so if anyone can help with either I would be grateful. My problem is that the last time I took it out I am pretty sure that the cylinder was letting some water in from somewhere. The plugs had evidence of this. Obviously this problem needs resolved and get the engine fogged and running to avoid rust. The engine seems too new for a head gasket. Which gaskets can let water in besides the exhaust pipe gasket?

Since I ran the battery down trying to start the engine after it bogging down that became my next priority but I fouled that up by getting in a hurry and switching neg and pos after charging battery. Horrible rookie mistake. I will try to check for fuses tomorrow. Are they int he electrical box area with the solenoid? Also what would disconnecting the red wire from the rectifier do?

Thanks for your replies

 

[timmyboy76]

parg.1...besides exhaust, head gasket will leak or crack somewhere. Guess compression test will letcha no, if cylinder/s need fix'n or new gasket.
parg. 2...any box that looks important, check the fuses, and for rectifier...The rectifier/regulator box does two things. It recieves AC voltage generated by the stator coils through the yellow wires. It then converts that AC power to DC power using the rectifier portion. The red wire sends back to the battery, regulated DC voltage to keep your battery charged while riding the ski.
When the rectifier quits working, that red wire is sending AC voltage to the DC battery. Your ignition runs off DC power as it is a DC CDI ignition. When AC is sent, it interferes with the DC CDI. If you can picture the static your car radio has when under high power lines you can understand how the AC effects the ignition.

A magneto produces very little voltage at lower rpm and more voltage at higher rpm. That is why the motor will start and run decent at lower rpm, but run very ragged at higher rpm when the rectifier is shot.

 

[GlglennGTX]

I tried the fuses on the MPEM they are ok

The seadoo still has no juice. The key does nothing. If I jump the solenoid the engine turns over. The fuses on the MPEM are ok. Are there any other fuses on the boat? Can I get the MPEM tested without the boat? Please help

 

[timmyboy76]

clean the post with soapy water, and swab out the landyard. Sounds now, if the mpem aint read'n the key..

 

[cut'n ride]

I have a brand new post that I'd sell you for a good deal if you want.

 

[Dennis]

Fuses

There are fuses in the rear electrical box also.
DAWG