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What size prop? - 1996 150 Evinrude / 74 Mako 20

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  • What size prop? - 1996 150 Evinrude / 74 Mako 20

    Good morning fellow Mako addicts! Hoping someone can point me in the right direction. I have a 1974 Mako 20 with a 1996 150 Evinrude Ocean Pro. I just purchased the boat this summer and only had it out about 5 times. Can't get past 4200 rpms - 31/32 mph.

    I was told this is a prop issue.

    Engine has a 14 1/2 x 19 aluminum prop. I want to get a stainless prop and looking for recommendations.

    Any help would be appreciated.
    Joe

  • #2
    good morning and welcome to classic mako. Your engine if in good tune and with the correct prop should reach 5500 rpms. LOTS of variables in play here.

    Does it have the correct shaft length for your boat. Originally your boat was a 20 inch transom. Your big wide cavitation plate above the prop should be at or just above the bottom of the boat when checked with a straight edge.

    Are all 6 cylinders firing. You can test this by pulling each one off one at a time while idling. You should hear a slight difference in the engine tone when doing so. Make sure to use a good pair of insulated pliers...

    with engine shut off, open the throttle handle all the way forward and check to see if the butterflies in the carburetor are opening up all the way. also check to see if any of the linkage is loose or missagusted.

    Try and borrow a 17 pitch good condition prop, and also a 19 pitch. note tach RPM's at wide open throttle going across the water with engine trimmed up a bit, with each test.

    If you just assume your prop is the problem you may just mask the problem with a prop change, your engine has to be running well in order to utilize the prop that is on it. The prop essentially provides your final gear ratio.

    Get a factory service manual for your engine. they are all over ebay. best 40 bucks you can spend.

    dave
    [br]1994 Mako 215 Dual console Optimax 225[br]1978 Mako 19 with 90hp johnson[br]1996 Mako 22[br]1982 Mako 171 Angler 135 Black Max Mercury[br]1987 21b 225 Yamaha[br]1974 23 inboard Gusto gone.[br]1979m21 225johnson \"blue dolphin\" bought off this board and restored [br]with everyone\'s help!!Gone but not Forgotten....[br]1979 20 Mako 115 Suzuki gone[br]1977 19 Mako 115 Johnson gone[br]1976 23 Mako twin 140 Johnsons gone[br]1983 224 with closed transom and bracket[br]And 162 SOB (some other boats)[br]Venice Florida, Traverse city Mi.

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