Weird Ultra 150 Issue

[99ultra150]

Last year I had a passenger on my Ultra 150, the weight limit was close, and I literally went from 60mph to 15mph top speed in a split second. When I run this thing on a hose I can rev it to the 8,000rpm limit; however, in the water it revs out to only 3900 and stops climbing. I can slowly get it to 20mph and that's it. Plus, it has a lot of problems starting. Since last summer as a trouble-shooting plan, I've rebuilt the carbs (were dirty due to previous owner letting it sit with no winterization), checked for proper spark and compression, and checked the jet drive system. The fuel filter and plugs have been changed and the gas tank was ciphoned and new gas put in. I had a prominent yamaha dealer in the area tell me it may be a temperature sensor/ECU thing protecting the engine. I had a kawasaki dealer check it and they saw no problems because it only has this issue in the water. BTW, this happened when the ski had only 90 hours on it! Anybody experience this issue????????????? Very frustrating

 

[kend301]

Re: Weird Ultra 150 Issue

I've rebuilt the carbs (were dirty due to previous owner letting it sit with no winterization), checked for proper spark and compression, and checked the jet drive system.

My only thought is what else did he miss ??? , Fuel problem is my first thought but the engine could be done also .. no way a ski can go that slow with spark and not cut out .

 

[The Penguin]

Re: Weird Ultra 150 Issue

similar issue on my (and other) superjets have always been electrical.

check your plug wires - including removing the boots and check the electrode to make sure you have good contact there.

plug wires do go bad as well - showing "good spark" on the trailer, but then not delivering good spark on the water.

 

[99ultra150]

Re: Weird Ultra 150 Issue

Thanks for the response guys. Fuel has checked out good, that's what I thought at first also. Partly why I started with the carbs and filter. I'm leaning towards electrical because reving stops dead at 3900 rpm in the water no matter what. Something seems to be "telling" the engine to take it easy! Plug wires are a possibility, and I thought of that. Just haven't focused on them because the rpms aren't erratic, but I could check them out to eliminate the possibility.

 

[99ultra150]

Re: Weird Ultra 150 Issue

Oh yeah...compression is good...I thought maybe the head gasket or rings, but I checked compression and so did the dealer. I've always owned yamahas before this and never had these types of weird things going on...frustrating.