90/65 Jet Only HItting 4300 RPMs

[MtAiryEd]

I have a six-month old Merc 90/65 jet on a 17' river jon-boat. I have about 25 hours on it. I took it out on Sunday on the Potomac River. The water temp was about 35 degrees. I launched the boat, started the motor, and let it run about 5 minutes. I then motored out about 50 yards and started increasing the throttle to full. The motor's RPMs climbed up to near max, then fell off a bit and stayed at 4300 RPMs. We shut it down and look under the cowling. We found nothing..no loose linkage, the jet's gate was fully out of the jet's way, nothing clogging the intake grate, 3/4 full 2-cycle oil reservoir, full gas tank. We started it up and ran up the river. Again, max was 4300. We fished around for a while. We started the motor a few times to run back up the river, then ran down to the ramp. Each time, the motor max'ed out at 4300. It ran great...no sputtering, no hesitation, always going right to 4300.

I called the guy who made my boat (custom job). He asked some basic questions. The one thing he said was that it might be some fail-safe mode where the computer is limiting the motor to lower RPMs. I'll be calling my local, authorized dealer, but I was just wondering if anyone had any ideas.

Thanks!

 

[Lone Duck]

Re: 90/65 Jet Only HItting 4300 RPMs

Yes it should run about 5300 to 5500. Is it a new engine ? Perhaps something in the throttle system has come loose from factory. I would have a dealer check it out . Might just be a loose throttle stop. Or they can tell you if it is something serious and you can decide your next move from there.

 

[MtAiryEd]

Re: 90/65 Jet Only HItting 4300 RPMs

Yeah, it's only six months old. I called the dealer. He said it might be running on two of the three cylinders. That would explain the consistency of it. Time to take it in.