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  1. #1

    Default 1984 Mercury Black Max 150hp - reverse problem

    I have a 1984 Mercury Black Max 150hp outboard. It doesn't want to go into reverse gear. It used too!! It runs perfect in neutral and shifts into forward gear fine. Any suggestions as to what to check or how to troubleshoot the problem? I had my wife stand by the steering wheel and move the gear shift back and forth. I stood by the motor and watched a shaft in front rotating back and forth. So the shaft is rotating. Thanks for any help. Steve

  2. #2
    Join Date
    Jun 2008
    Malden, MA,

    Default Re: 1984 Mercury Black Max 150hp - reverse problem

    pull the lower unit and see if it shifts into reverse. If it does, you might need a new cable. IF you do a search in this forum, you can find some other answers too.

  3. #3

    Default Re: 1984 Mercury Black Max 150hp - reverse problem

    I got the reverse fixed. I thought I would tell what I did for the benefit of others. I had previously pulled the lower unit ( approximately two years ago) to check the water impeller (the impeller was fine). This must have been when I lost reverse.

    Like emac said, I repulled the lower unit to check shifting. Thanks for the suggestion emac. I had used the motor in saltwater and the lower unit did not want to come off. There are six bolts that hold the lower unit on. One is concealed under the sacrificial anode. Two are slighly rear of center, two are slightly front of center. Then there is one bolt in the very front. The bolt in the very front gave me problems. The nut came off easy enough, but the shaft of the steel stud (bolt) seemed to be seized to the aluminum. I took a half inch by twelve inch brass punch and a large hammer and started to pound on the top of the stud. I wacked it repeatedly and pretty hard till it was flush with the aluminum housing. Then I took a tapered steel drift punch about a foot long and drove it the rest of the way out. Off came the lower unit. Needless to say the threads on that one stud were slightly buggered. I took a eight inch long strip of fine emery cloth and polished the end of the stud. Then I rethreaded it with a 7/16 inch fine thread die. I polished the shaft of the stud with the emery cloth strip. I redrilled the aluminum housing hole with drill bits so there was clearance.

    I checked shifting by attaching a small vise grips to the shifter shaft and rotating it both ways and then checking the propeller rotation direction by turning the driveshaft with both hands. It seemed to work fine.

    Now I was ready to reattach the lower unit. I was going to be extra carefull this time. First I made sure the lower unit was in neutral. I did this by turning the drive shaft with both hands and making sure the propeller was not rotating. Then I made sure the gear shift by the steering wheel was in neutral. This is where I think I went wrong the first time I had the lower unit off. Both the lower unit itself and the gear shift have to both be in neutral. Otherwise you won't get enought shaft rotation to get it to go into reverse.

    Reattaching the lower unit can be an exercise in frustation. This is what I did: Reattach the lower unit part way. Then position the motor in the stright up and down position using the power trim. I used 3/4 inch pine boards under the skeg to hold the lower unit up (It's pretty heavy on the 150hp and you need four hands). Next make sure you have the water tube lined up. Engage the drive shaft by turning the flywheel slightly and lifting up on the lower unit. Keep adding pine boards as needed to hold the lower unit up. Attach the two nuts that are located slightly front of center part way. Leave the washers off to do this. You will remove the nuts later to add the washers. Now you have to make sure the shifter shaft is lined up. Put a small tapered-nose vise grips on the upper shifter shaft to line it up. The splines must match. Good luck. Keep tightening the two attachment nuts. Then remove the nuts one at a time to add the washers. Finely, tighten all six nuts/bolts. Put moly grease on all the bolts/ shafts/ nuts to prevent future seizing.

    Hope that helps someone.
    Last edited by Steverino; 08-08-2011 at 05:12 PM.

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