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No power over 3500rpm

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admjr47

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Twin 5.7’s. One is brand new with 2 hours. Runs perfect. Other is 1 yr old with 10 hours. So far, we change the carburetor fuel pump Cap, Rotor wires plugs all the fuel filters, water separator filter checked the gas lines ran it on an individual tank and still have the same problem. One engine goes to 4800 RPMs this engine will not go over 3500 RPMs it doesn’t bog it doesn’t sputter They idle beautifully. It just will not go over 3500. We even switched the carburetors on the motors to see if the problem follow the carburetor and it did not follow it. It’s definitely something in the motor. Is it possible that the problem is in the out drive?
 
admjr47 said:
Twin 5.7’s. One is brand new with 2 hours. Runs perfect. Other is 1 yr old with 10 hours. So far, we change the carburetor fuel pump Cap, Rotor wires plugs all the fuel filters, water separator filter checked the gas lines ran it on an individual tank and still have the same problem. One engine goes to 4800 RPMs this engine will not go over 3500 RPMs it doesn’t bog it doesn’t sputter They idle beautifully. It just will not go over 3500. We even switched the carburetors on the motors to see if the problem follow the carburetor and it did not follow it. It’s definitely something in the motor. Is it possible that the problem is in the out drive?
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Maybe there's an issue with your throttle linkage on the struggling engine and the throttle plate isn't fully opening.
 
We checked the carb while underway and it’s opening correctly. Also replaced all cable linkages throttle controls and upper and lower shift cables.
 
1. Have you checked timing at 3500 rpm and compare to good running engine?
This will show if timing control is working.

2. Is this condition when running under load or in neutral? Or both?

3. Any outdrive work/changes.

Any history or changes that had been done prior to this issue?

A compression check may be needed as well as 100% confirmation of plug wire firing order.
 
I will try the above. But no changes were made. Happens under a load. Fuel pressure is good at idle and under load timing is good
 
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