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Nissan 2002 9.9 motor power loss

E

ebeeiii

New member
I have a Nissan 2002 9.9 motor, Starts up on the 2/3 pull, in neutral the engine runs strong with no backfiring. Have check and or replaced with new – Fuel filters and lines and fuel tank drain/cleaned, spark plugs (gap at .035) and wires. It is mounted on a 14.5 Aluimnacarft boat and at 50% to 70% seems to run find (not much change in power) but the boat never plains out. From 70% to 100% very little change in power, sound and from what I can tell not much in RPM. It seems that engine has a governor on it and holding it back.
Ed
 
Sorry been away on Family Buss. Ran it, took every thing off of the boat I could and check it with a tach, 2800 to 3200 rpm. Change the Prop. to a 9.2/6.9 and it's running at 4200 to 4400 rpm. Still dosen't plain but is better than it was before. Looks like I will need to upgrade to a larger motor.

Thanks for all your help!

Ed
 
The only prop lower than that one is only going to boost it up another 200 RPM...Just an idea. By any chance is the engine sitting directly on the top of the transom without any kind of block to bring it up to the right height?
 
I just pull out the spec, 0.2 to 1" from the bottom of the hull to the bottom side of the Aniti-Ventilation plate. Will check it tonight.

Thanks, Ed
 
The "rule of thumb" is that the antiventilation plate runs in a range 1 inch above or below the bottom of the hull. Lower is slower, higher is faster. But you will want to do actual on-water sea trials to confirm the best jack height.
 
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