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Old 05-03-2013, 05:51 PM
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JimN JimN is offline
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Join Date: Jul 2004
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Originally Posted by skiknox View Post
Fuel psi at key on 42
At idle dropped to 38
Through full rpm range 42-43
Boat runs smooth and no hesitation to 4000 rpms but that's it
Butterfly's on tb are opening all te way took filter off to comfirm
GPS speed was 41.5 wot

Thoughts???? I'm stumped
What's the diameter and pitch of the prop? If it's cupped and the pitch is excessive, it won't rev as high as it should.

Did you verify base timing by putting the ECM in diagnostic mode? A couple of degrees off can affect top end. I would put the timing light on it and check this, and leave it on so you can see total timing advance when it's being driven. If you don't see a major change in total advance, something is wrong. You should be at 10°BTDC at idle and it should be rock steady. If it jumps around, there's nothing wrong, but it's not in Diagnostic Mode. Use a paper clip as a jumper for terminals A and B on the ALDL (Diagnostic Port, at the rear of the engine- ALDL stands for 'Assembly Line Data Link). Do this with the engine off, start it and manually maintain 1000RPM when you check the timing. Set it to 10°BTDC, snug the distributor hold-down, re-check/reset to 10° if it moved and tighten it. If it's off by 1°, don't freak out but try to hit the number. After shutting it off, remove the paper clip and cover the ALDL before running it again.

The paper clip can also be used to read codes on the check engine light.
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