1970 25 hp johnson pontoon motor- can i shorten the shaft?

Discussion in 'Bubba's Outboards' started by dip, Jul 3, 2008.

  1. dip

    dip New Member

    Messages:
    203
    State:
    stinkin ohio
    i got a great deal on a solid running motor but discovered that it is 2" too long and the resulting drag has my boat only doing about 13 mph versus 24 mph on the merc that died on me. i have thought about buying a jack plate to raise motor but since i want to buy either a new motor or a new rig next year i decided not to alter transom. so, can i shorten the shaft?
     
  2. Duckpoor

    Duckpoor New Member

    Messages:
    184
    State:
    Illinois
    John ,
    Picking up 9-10 mph is going to be a big job but reading your post I thought about what would be simple to try to make sure your going the right direction.
    Those motors i believe came in 15 (short shaft) and 20" ( long shaft) stem lengths .
    Most of the ones we have messed with do benifit from raising them up to almost the point of cavatation. As long as they don't slip the prop and still cool fine you can go up as far as the transom clamps will let you.

    What comes to mind is the prop . If that motor is tryiing to pull to big a wheel the RPMs would be down and he would be short of power. To small and the result would be tons of revs and heck of a hole shot but short on top end.

    Just something to get the visit started. Those Old OMC are good motors and make as much power as anything in their class.

    Looking forward to see what ya fine.

    Good luck .

    R Green
     

  3. dip

    dip New Member

    Messages:
    203
    State:
    stinkin ohio
    thanks duckpoor but this one has about a 22" shaft for pontoons or sailboats or whatever. that is why the things hangs about 2" too low. the drag kicks water up between the motor and the transom. that is what slows me down. i need to know if i can remove the 2 or 3" inch extension that makes this hang too low.
     
  4. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
  5. dip

    dip New Member

    Messages:
    203
    State:
    stinkin ohio
    thanks bubbakat for answering my question. that is a brilliant (and cheaper) answer to the jack plate problem but i'm still not sure i want to drill more holes in the transom when i look to buy a new motor next year that would be the right length.