OMC 115 TurboJet losing RPMs

[MikeeH]

[FONT=Verdana, Arial, Helvetica][FONT=Verdana, Arial, Helvetica]Im not even certain this is the correct forum but here goes! Its a 115HP OMC/Johnson TurboJet which is actually an OB motor attached to a Jet Drive in a 1996 Boston Whaler Rampage 15. (Don't judge me, it was a freebee from a friend ). The boat is in great shape and the motor runs fine up to 3000 RPMs, in fact, it seems like it will run all day up to 3000 RPMs. But once you push it past that mark the RPMs drop way off until you back off to idle and then throttle up again to the 3K mark. Then, as soon as you push past 3K it drops off again. Previous owner says the carb has been rebuilt, in-line fuel filter change and fuel lines replaced.. all appears visually to be true. It performs the same way under load and in neutral. I already verified that the oil is in the gas by actually mixing it in the tank rather than chancing on the oil injection pump. So WTH??? It certainly seems to me like a fuel starvation issues but I know little about 2 strokes and even less about outboards but I have found a service manual which really isn't helping to diagnose this issue. Thanks for any ideas on where to go next... or again.[/FONT] [/FONT]

[FONT=Verdana, Arial, Helvetica]Mike[/FONT]

 

[boobie]

Check your compression.

 

[racerone]

Agreed ----The #1 thing to check on that crossflow.---------Did a turbojet a while ago and found one side of a carburetor with 2 high speed jets in the hole.----Never saw that before and likely will never see another crossflow with the same issue.

 

[boobie]

Racer, many years ago I found the same thing.

 

[racerone]

I counted them / checked again and again as I could not believe what I found.----Possibly unhappy employees who could see that things were going wrong with OMC and boat companies ??

 

[boobie]

Or else BIG hang overs. Been known to happen. Experience talking.

 

[MikeeH]

Not quite sure I understand the relationship between the jets in the carb and compression (or perhaps I'm misunderstanding the conversation.). That said, I can easily check both but I'm not sure that is where the problem is since the previous owner said the problem described was a sudden onset and the motor was running fine up until the moment the problem appeared. Continued research has me thinking its electrical and I'm leaning towards a faulty "power pack". Unfortunately I know of no means of doing any diagnostic work on that so I may have to just bite the bullet and spring for a replacement.

 

[racerone]

Yes a new powerpack fixes these problems 9 out of 10 times.----Worth a try.