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  1. #1

    Default Classic 50 Loss of Power and Reduced RPM

    Motor Info:

    Serial No: A999862
    1986
    4 cyl.
    MERCURY 45 ELPTO
    PARTS CATALOGS: 13287 - 45/50 Hp
    WOT: 5000 - 5500
    Mixture: 50:1
    Gear ratio: 1.83
    Prop

    • 13 splines
    • 10 5/8 diameter by 12" pitch Black Max prop?

    Gear Oil - 80, 90, or 80w-90 GL-5


    Problem:

    Motor ran fine last few uses. On my previous trip, from the launch, she was slow to get up, and was running slightly rough at WOT. WOT decreased by maybe 500 RPM during the trip out. Spent the night out.

    On the return trip, she was even slower to get up. WOT decreased significantly to about 2000 RPM and even that 2000 RPM didn't seem like it would a typical full-power 2000 RPM. Running a little rough, not a consistent miss, but an occasional one.

    Back home on muffs, started fine, idles fine. Still slightly rough when the RPMs are raised on muffs. Stated doing something new... would idle fine for a while, then RMPs would jump from around 1k to around 2k. Seafoam additive in fuel, Seafoam carb cleaner in carbs. Started and idled slightly better, but not significant change besides that.

    Noticed water coming out of the engine through a hole to the left of the top spark plug. Research indicates that it's a block cover gasket issue.

    Back in the water today. Will get to about 4000 RPM, but the power is not there. Running rough at higher RPM, but hard to call it a consistent missfire... but maybe. Idles fine.

    It doesn't seem that the the block cover gasket would allow water to get into the cylinder and cause a power loss. Plan to change, but want to get to the root of the problem as well.

    I will run a compression test, but in the meantime would like to start getting the advice below.

    Requests:

    1) Best plan of attack?

    2) Could it be water getting in under higher pressure (when RPMs are up) from another gasket (cylinder black to baffle or baffle to exhaust)? Could this be causing the power loss?

    3) Can someone share the correct parts diagram for this motor?


    Thanks!

    Mel

  2. #2

    Default Re: Classic 50 Loss of Power and Reduced RPM

    I had a similar problem with my motor. The issue with mine was the gas tank fitting was broken causing air in the line. Check your fuel line from the carb to the tank and see if anything is wrong with it. If that's not bad check and make sure you have spark on all cylinders. Then check compression. The compression should be pretty even between all cylinders. If that checks out try having some one pump the bulb while it does it. It it gets better when that happens the fuel pump is bad. If after you check all that then Id clean the carbs.

  3. #3
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,271

    Default Re: Classic 50 Loss of Power and Reduced RPM

    My best guess is that the high speed coil on the stator is not working. If you can borrow a DVA meter, the red wire should be putting out at least 50 volts at idle.

    Jeff

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