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    1974 15hp evinrude low compression help...

    motor starts easy and runs good. but has low power and wot rpm. compression is 35psi in both cylinders when spinning motor by hand. I even compression tested both cylinders while running on one and testing the other and still only got 60psi. removed bypass plate, pistons are clean and smooth...
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    1974 15hp evinrude low wot rpm with factory prop?

    Re: 1974 15hp evinrude low wot rpm with factory prop? ive also been working with those issues. I had to cut the 20" transom down to 17" to work with the short shaft motor and im still thinking I may need to go an inch lower. trimmed down the plate is even with the bottom of the boat but the...
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    15hp evinrude, need help choosing new prop.

    Re: 15hp evinrude, need help choosing new prop. thanks I read over the info. im still not sure to drop my motor another inch or raise it. the attached pictures show the the trim set to the 3rd hole the plate sits about 3/4 inch above the bottom of the boat but I have such terrible prop...
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    1974 15hp evinrude low wot rpm with factory prop?

    I recently fixed up a 1974 15hp evinrude model 15404s. it has new fuel pump and lines, carb was cleaned, new head gasket, new everything to do with the cooling system. the motor runs great but after test runs my wot is 4320rpm with the factory 9 1/2x10 prop and I need to be running between...
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    15hp evinrude, need help choosing new prop.

    Re: 15hp evinrude, need help choosing new prop. I have not felt any cavitation since lowering the transom and at full throttle the motor runs very smoothly I don't know what rpm its running at full throttle but from the sound of the engine I seriously doubt its anywhere near 6500. I ordered a...
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    15hp evinrude, need help choosing new prop.

    Re: 15hp evinrude, need help choosing new prop. yes with the 3" notch the transom is now 17" tall. I didn't want to go lower because I wont be able to keep my 45deg sides due to the transom braces. without at least a 45 on the side cuts my steering will be blocked. if I do need to go lower when...
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    15hp evinrude, need help choosing new prop.

    I recently rebuilt a 1974 15hp evinrude model 15404s, now runs like a champ but may be pushing too much boat. I mounted it on a aluminum flat bottom that measures 15'10" x 50" with the factory prop I have good idle speeds and maneuvering and very nice take off that lifts the bow nicely but tops...
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