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RSRBOB, Technician
Category: Boat
Satisfied Customers: 1078
Experience:  Former Yamaha Factory Service Rep, Dlr Line Tech, Serv Mgr, G/M
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I have a yamaha exciter jet boat, single 135 hp, 2 stroke engine.

Customer Question

I have a yamaha exciter jet boat, single 135 hp, 2 stroke engine. It won't rev over 35k RPM and it is also not peeing. I tried flushing it this morning with the hose adapeter per the users manual, but still didn't pee. Any ideas? I'm a car mechanic, but not the best with marine engines.
Submitted: 2 years ago.
Category: Boat
Expert:  RSRBOB replied 2 years ago.
Hi and thank you for your question.
First, there is a better than average chance that the 2 problems are not related. The lack of the water spray out the tell tale hole could be as simple as a restriction in the hose. Try taking a straightened out coat hanger and inserting it in the hull fitting and gently inserting it in the hose as far as it will go without forcing it. Critters love to make homes in those hoses so this is a fairly common problem.
Now on to the engine, if the engine will "never" exceed 3500 RPMs, it is either getting a false overheat signal or it has a mechanical problem internally in the engine.
The first thing I suggest is running a compression test on the engine to determine the mechanical soundness of the engine. It is always best practice to start there first. If the compression checks out within spec then take the ignition box apart and unplug the pink wire from the CDI box. This takes the overheat sensor out of the system. If the engine runs normally with that unplugged, you will have to replace the overheat sensor unless you see an obvious problem where it appears to be pinched and grounding out.
Let me know if you have any more questions.
Thanks Customer
Customer: replied 2 years ago.
I checked the compression. I have 110, 65, and 105psi. My question is, can I just rebuild the top end? I hate to drop $1k on a reman motor.
Customer: replied 2 years ago.
Oh, and i ran weed eater line down there, and it cleared it out. Even if compression is low in the #2 bank, still seems like it should still turn over 3500 rpm, no?
Expert:  RSRBOB replied 2 years ago.
Thank you for the additional information.
Glad you got the tell tale outlet cleaned out.
Yes, one cylinder can be very detrimental to engine performance. It could quite possibly be more than just dead, it could be creating additional friction restricting RPM's.
You can definitely rebuild just one cylinder. Yamaha has oversized piston and rings available.
Take a good close look at the crankshaft though. Make sure there is no debris from the top end failure in the crank area. If there is, as soon as you start it back up, it will get pulled up into the top end and quite quite possibly ruin your fresh rebuild.
If you have any more questions, feel free to ask.
PS, you need to find out why cyl 2 failed. Check the oil line going to the carb. Make sure it did not come off.
Thanks Customer

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