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Have 94 speedster-both engines run fine until about 4000 rpms-when…

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have 94 speedster-both engines run...
have 94 speedster-both engines run fine until about 4000 rpms-when increase beyond that, right engine zooms up to 7000 rpms until I back it down to the 4000 range again-any idea what the problem is?-thanks
Submitted: 3 years ago.Category: Boat
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Answered in 1 hour by:
5/31/2015
Marine Mechanic: Joe, Marine Mechanic replied 3 years ago
Joe
Joe, Marine Mechanic
Category: Boat
Satisfied Customers: 7,426
Experience: ASE, electronics, Marine mechanical and electronics, pwc, wiring, all around repair tech,
Verified
Hello,
Thank you for allowing me to assist you, my name is ***** ***** I will be happy to assist you with your concern today.
If the engine runs off high rpms like that on it's own this usually indicates an air leak and the engine should be pressure tested/leak down test. Common areas are intake gaskets, carb mounting gaskets, reeds, case gaskets, crank seal, etc including the leaking of the rotary valve assembly. Air leaks on a 2-stroke allow extra air to which it will start to draw it's own fuel and engine will run off on it's own. This is usually causing a lean condition which if not corrected can also lead to top end failure.
Thank you!
- Joe
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Customer reply replied 3 years ago
Would it still be OK to operate the engines at an RPM level (4000 rpms) where the right engine did not run to the 7000 rpm level or would this still do possible engine damage?-any estimaye on cost to repair such an issue????-thanks
Marine Mechanic: Joe, Marine Mechanic replied 3 years ago
I would not, no. You may also want to check the impeller and wear ring along with the pump for damage, depending on when and how far throttle is advanced such as if it's full throttle when this happens then it may be sucking air due to pump, impeller or wear ring issues. The impeller and wear ring should not have much distance between them when checking and no gouges or chunks. This is for instance if you go to take off full throttle and one engine goes full rpm right away and other is lower as it is building speed. Air leak would normally be say your half throttle and this happens.
Thanks,
Joe
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Customer reply replied 3 years ago
I appreciated your prompt response and your suggestions as to what might be causing the problem-until I'm actually able to look at the potential problems areas you noted more closely and do some further water testing, I won't be able to accurately assess how helpful your information was-at least you provided some good starting point which I didn't have before-should I have any further subsequent questions, can I still contact you or do I have to pay another fee?-thanks
Marine Mechanic: Joe, Marine Mechanic replied 3 years ago
Good afternoon,
I greatly apologize for the delay in my reply to you.
You can reply back to me at any time without further fee so long as it remains under this exact question and is part of the same problem. In any event you can always reply back at any time to me and I will be sure to reply back to you as soon as I am able, which generally is quick with some exceptions.
If you do need any further assistance please let me know.
Thanks again,
Joe
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