1998 Johnson Torque Pull

[eddy2419]

I went down to a 15"x15" prop from a 15"x17" on a 1998 Johnson 150 Ocean Runner on a 21' CC. I also replace the steering mechanism. I now have a lot more pull to the right on the wheel (have to keep counter-clockwise pressure on the wheel). I am assumming it is from the increased torque of the 15" pitch. The boat really has a lot more response to it now.

I tried to compensate by turning the fin toward the direction of the pull. I loosened the bolt in the middle of the fin and tried to turn it but there is very limited adjustment.

Am I missing something here? Anyway to get more adjustment?

Thanks

 

[noelm]

Re: 1998 Johnson Torque Pull

you need to make sure you moved the little "fin" the right way, you are steering the motor not the boat with it, so if the boatsteering pulls to the right, then the rear of the fin needs to be moved to the right, which will steer the motor as if you are turning left!

 

[Chris1956]

Re: 1998 Johnson Torque Pull

Eddie, I have the same motor on a 21 dual console, which I would think is heavier than your 21CC. I get 42MPH @ 5250 RPM with a 15X17" standard OMC aluminum prop. What kind of performance do you get after moving down to the 15" pitch prop?

 

[eddy2419]

Re: 1998 Johnson Torque Pull

I couldn't hit 5,000RPM's with a normal load with the 17 which was probably an OMC prop. That is why I went down. Before I ran it any I also added a t-top so my comparisons wouldn't be very valid. I could squeeze out about 39-40MPH at 4800 RPM's and a moderate load before. Now with a full load and t-top I am at about 34 MPH. 4200 RPM's and 33 MPH seems to be my cruise spot. I have a 98 Wellcraft CC which is not a "light" boat. No coring, all plywood under the deck or solid glass. Dry with engine it is about 3300 #'s.

The big difference is in the response. Much faster to plane and accellerates much faster. More than I would have expected going down just 2". I'm sure I lost some top end and will experiment with the old 17.

What is your most efficient cruise RPM's?

 

[Chris1956]

Re: 1998 Johnson Torque Pull

Eddy, Thanks for the info. I think my 21DC is about 2800# + motor (350#), so it is lighter than your boat, it would seem.

When I checked the A-V plate against the bottom, the motor was a bit low on the transom. I need to do some testing to see if the boat ventilates in high speed turns, before I raise the engine. I guess the thing that mystifies me is that the boat pops out of the hole, has good power all the way up the RPM scale, and then only gets to 5250RPM and 42MPH. I guess I am not used to a motor having this much low end power. My speedboat with the Merc 1500 is a bit slow to plane, but then accelerates extremely fast. If you are skiing, and the driver doesn't throttle back, you go airborne.

 

[eddy2419]

Re: 1998 Johnson Torque Pull

You may want to borrow a 19 to try out. Seems it would give you better top end but less pop.

 

[Chris1956]

Re: 1998 Johnson Torque Pull

Eddy, I have a 19" prop from my Mercruiser Alpha I drive that I drilled to fit my Johnson. I haven't tried it yet, but will probably try it after I raise the motor, should I decide to do that.