Results 1 to 3 of 3

Thread: Hotrodding a 25 Yamaha 4 stroke

  1. #1

    Default Hotrodding a 25 Yamaha 4 stroke

    got a 25 yam 4stroke on a 16' alumaweld jon boat; boat goes okay just everyone blows our doors off on the river; have the 2 props (torque/speed) for it. Any way to squeeze a few more ponies out of these motors without adverse consequences? Don't use it enough throughout the year to warrant a higher hp motor but boat is rated for up to a 40 tiller also concerned about more weight on the transom going to a larger motor.
    Jim

  2. #2
    Member wolfkiller's Avatar
    Join Date
    Sep 2006
    Location
    north pole ak
    Posts
    408

    Default Probably not

    Quote Originally Posted by Big Jim View Post
    got a 25 yam 4stroke on a 16' alumaweld jon boat; boat goes okay just everyone blows our doors off on the river; have the 2 props (torque/speed) for it. Any way to squeeze a few more ponies out of these motors without adverse consequences? Don't use it enough throughout the year to warrant a higher hp motor but boat is rated for up to a 40 tiller also concerned about more weight on the transom going to a larger motor.
    Jim
    Most mods you will feel will shorten the life and reliability of your motor.
    A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.

    www.arcticconcealment.com

  3. #3
    Moderator Paul H's Avatar
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    5,594

    Default

    When you need more engine, you need more engine. Outboards already get a decent amount of power out of relatively small displacement engines, so w/o signifigantly altering the engine get it to rev higher or run higher compression ratio, you just aren't going to be able to see signifigant gains in power. And if you do raise the operating rpm of the engine, more than likely you'll kill the low end and find that the motor won't lug any sort of prop.

    With the Kenai regs now banning the two strokes, you shouldn't have much trouble finding a 35-40 horse two stroke at a pretty reasonable price. That would far and away be your best option. There ain't no replacement for displacement

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •