85 hp Force High Speed

Discussion in 'Bubba's Outboards' started by duanestuck, Aug 7, 2006.

  1. duanestuck

    duanestuck New Member

    Messages:
    4
    State:
    Illinois
    I have a 1988 85hp Force outboard. It runs fine, but the top RPM is only 4000. How can I increase the top RPM to near 5500?
     
  2. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    First you need to find out why your only getting 4000 rpm's.

    Engine operating properly?

    Set up on the boat?

    Right size prop?
     

  3. duanestuck

    duanestuck New Member

    Messages:
    4
    State:
    Illinois
    Well, the motor runs fine, although I have not checked the timing. It has good power all the way to full throttle, but simply doesn't go beyond 4000 rpm. Propellor is what is called for in Owner's Manual (13 X 19).

    I thought perhaps there is a full throttle adjustment that I am overlooking.
     
  4. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    That could be. On some engines, thre's a rubber/plastic round cam follower that is part of your linkage. The deteriorate and fall aprt.

    Look into your carb, with full throttle open. if the throttle plate edge is not facing fully to the front, then it's not opening fully.
     
  5. duanestuck

    duanestuck New Member

    Messages:
    4
    State:
    Illinois
    Thanks. Will do.
     
  6. WishinIwasFishin

    WishinIwasFishin New Member

    Messages:
    23
    State:
    Georgia
    Years ago I bought a new boat and motor. The first time I took it to the river it would only turn about 4000 RPM. I took it to the best mechanic I know. He checked it with a machine and said that it was putting out the HP it was supposed to. Said that the design of the boat required a smaller prop. I changed props and the motor turned up to about 5800 RPM. This was the max allowed. Boat didn't go any faster but did plane quicker and reached maximum speed quicker.

    This boat is designed to run in shallow water flats. There is a hook in the hull to hold boat level. This reduces maximum speed because of drag.
     
  7. duanestuck

    duanestuck New Member

    Messages:
    4
    State:
    Illinois
    The propellor has a significant chunk out of one of the blades. Would this reduce the RPM?
     
  8. Mr.T

    Mr.T New Member

    Messages:
    2,553
    State:
    MO
    A chunk out of the propeller shouldn't reduce top end RPM by that much, but if the chunk is "significant" as you say, it's going to eventually tear your lower unit apart from the unbalance and vibration.

    13x19 sounds like too much prop for an 85 hp to me, but if that's what the manual calls for... Of course, the manual is just a guideline - the "right" prop for every engine/boat combination will be different.
     
  9. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Talk about your boat.

    What kind, size , hull style.

    Engine placement, possibly too low.

    Have you tried another tach, maybe the one you have is bad.

    Pop? Get it fixed now.
     
  10. savage308

    savage308 New Member

    Messages:
    399
    State:
    Victoria, Texas
    Fix or replace the prop now or be prepared to spend 2k for your lower unit.........