Boat pulls to starboard

[HotTommy]

I'm trying to get my pontoon boat to go straight under power. Some of what follows probably has nothing to do with the problem, but I'll include it all just in case. Here are the facts:

• 24' boat about 20 years old with two U-shaped aluminum pontoons
• 1995 Force 90 HP outboard
• I recently purchased and rebuilt the boat from the deck up
• The boat sits level in the water and there are no apparent reasons one side would drag more than the other.
• There was a crack where the motor mount pod attached to the port pontoon that was repaired by welding
• I replaced the old wooden transom with a new one I fabricated. I was careful to match the shape and mounting holes of the original.
• The boat pulls to the right under acceleration and while cruising near full power (about 20 MPH).
• The trim vane on the lower unit near the propeller was already adjusted with the rear of the vane fully to the starboard side.

The problem is more of an aggravation than a serious concern, but I'd like to fix it now if it isn't too big a job. If it is a big job, I'll wait until this fall when i pull the boat out for the off-season. .... It has occurred to me that as the trim vane was already adjusted fully to the starboard side, the previous owner had the same issue. That could mean that the transom geometry I copied with my new one was not correct. Thus the motor could be slightly off the boat's center line. I suppose it's also possible the transom is not square to the centerline of the boat. Other than these possibilities, what else might account for this problem? Does anyone have any idea of what else I might try?

 

[The Rooster]

Re: Boat pulls to starboard

Yes Tommy, if that torque tab, "trim vane" has already been adjusted, its got to be an alignment issue like you said. Should not be that hard to determine if the back of the deck or motor pod is square. Is the steering cable in good shape? If it turns out to be an alignment problem, you should be able to compensate w/ small adjustments to the motor pod itself. Could be a PITA, but doable. Good luck !!!

 

[HotTommy]

Re: Boat pulls to starboard

It occurs to me that a larger trim tab might help. Do they come in various sizes?

 

[The Woo Woo Kid]

Re: Boat pulls to starboard

Hey, I know....Have all the passengers lean hard to port.

JK, hope you get it resolved.

 

[Old Screwball]

Re: Boat pulls to starboard

Try moving the tab a click port. Sometimes you can over compensate. Good Luck!

 

[HotTommy]

Re: Boat pulls to starboard

OK, here's what I've found so far. T-H Marine sells an aluminum tab that attaches to the skeg specifically to help with motors that torque steer to the right. Here's a link showing how it attaches: click here. If I get one and try it out, I'll report back with results.

 

[Silver Eagle]

Re: Boat pulls to starboard

When I had my 21 ft speed boat mine always pulled to the right. It's the motion of the prop right turn prop boat will pull to the right.I also had to do a weight change .more people on the port side to level boat.

 

[HotTommy]

Re: Boat pulls to starboard

I tried the T-H marine tab and here's my experience. First, the tab is smaller (thinner) than I expected. That's good for keeping drag down, but limits how well it can serve as a trim tab. Second, the skeg on my motor is too short to mount the entire tab, so I had to cut off about a third of it to make it fit. Finally, it made a modest difference, but it did not solve the problem to my satisfaction. It looks like I'll be rearranging the transom mount points this winter.

 

[lakegeorge]

Re: Boat pulls to starboard

I tried the T-H marine tab and here's my experience. First, the tab is smaller (thinner) than I expected. That's good for keeping drag down, but limits how well it can serve as a trim tab. Second, the skeg on my motor is too short to mount the entire tab, so I had to cut off about a third of it to make it fit. Finally, it made a modest difference, but it did not solve the problem to my satisfaction. It looks like I'll be rearranging the transom mount points this winter.

Can you put a spacer behind the clamps on the motor where it attaches to the transom? that way you will be able to tell if that's the problem without ripping everything apart. If it corrects the problem then take it from there.

 

[MH Hawker]

Re: Boat pulls to starboard

I would lay a level across the motor pod and jack up one side of the boat and trailer it till it is level then see what the motor is like. Then you will know and not be guessing. I would bet its out of square. I have had to do that on a few older boats that have had the transoms replaced.

 

[HotTommy]

Re: Boat pulls to starboard

Perhaps my view of the situation is not correct, but here's how I see it. If the motor is mounted on a transom that is not square to the centerline of the boat, the motor should simply rotate on its mount when the boat starts moving. The only symptom would be that the steering wheel would be offset when steering straight ahead. My opinion is that the motor is mounted slightly port of the centerline of the boat. Thus the thrust is pushing the boat starboard as it pushes it forward. That is the symptom I am seeing. ... Now if the entire pontoon boat structure is out of square, that could also be the problem, but that's a much bigger issue to address.

 

[MH Hawker]

Re: Boat pulls to starboard

The thrust of the motor would be off to one side and not equally applied to both pontoons sort of like a steering tire thats about hafe flat it pulls to one side.

In the past I have ran across several transoms that have been replaced and the new wood was cut off of center and then the motor was dropped on to it and it was pushing the boat side ways and you get the hard steer to one side or the other. The way I have checked it it to put a level across the back cross members and the pod and jack up what ever side is low till it goes to level then use 2 plumb bob`s attached to the transom on each side of the motor clamp bracket and then you can measure to see if its on or off center, if its off center its a simple matter of moving the motor left or right and drilling new holes. I have found a few that were off center by 3 inches and it made a noticeable pull.