pulling to the right

[retaunton]

I have recently put a 2005 15hp 4 stroke Yamaha on a 14ft jon boat. I have it at the proper hight and center. It has the preset trim tab but it still pulls hard to the right. could it be the prop? Thanks, Robert T.

[robert graham]

Maybe loosen the bolt and reset that zinc trim fin under the ventilation plate...turn the back of the fin all the way to the right(starboard)looking at the back of the motor. Tighten that bolt down good, as they have been known to vibrate loose and lose the trim fin. Good Luck!

[retaunton]

pulling to the right

Thanks Robert, for the reply. On this motor the trim fin is set with two screws that lock into off set holes that prevent any adjustments to the fin. After trying to raise and center the motor in different positions I even removed the trim fin and that did not help. I even ground the bottom of the fin flat so that I could adjust it as you mentioned and after drilling out the mounting holes on the fin to enable more travel it was obviously going to catch water on the left side but it continued to pull hard to the right.
I had an old pull start 15hp Johnson on this same boat before I upgraded to this Electric start Yamaha and it ran straight. I like this new motor it cranks and runs great but you better not let the tiller slip out of your hand or you will be turning around.
Hope we can figure it out. Thanks again, Robert T.

[robert graham]

It is possible to fabricate a thin(1/16") stainless steel plate and fasten to the rear(trailing edge) of your skeg with a few very small metal screws, then bend the plate right or left to provide the desired trim. Some of the newer Yamaha outboards have curved skegs to provide trim. Lots of ways to skin this cat!

[retaunton]

Sounds like a plan. I will give that a Try.
Just out of curiosity. What would cause a motor to pull like that?
Thanks again, i'll let you know how it turns out, Robert T.

[robert graham]

If motor is clamped to transom would it help to shift the motor left or right of center to create a "trim" effect? Is weight in boat distributed evenly?...maybe redistribute weight left or right to help with trim. It's hard to understand a 15HP motor's prop creating that much torque steering? Cups or dents in bottoms of flat jon boats can cause boat to pull one way...is hull O.K.?

[retaunton]

Hull is good and I did slid the motor to the left of center a little but I have not tried it to the right yet. I have the weight distributed good. The motor is level. It's a real head scratcher though.
We will get it figured out though.
Thanks again, Robert T.

[spinner1606]

pulling to the right

I have a 2005 0r 2006 15 HP yamaha 4 stroke on 14.5' jon boat(36"bottom)and have the exact same problem. I bought it new from a dealer and he told me to adjust the zinc trim fin under the ventilation plate. He later found out it CANNOT be adjusted! Sounds like it is a design problem to me. The 15 HP meccury 2 stroke I was running before on the SAME BOAT did not pull at all. If I knew how to contact Yamaha tec support directly I would. Surely there has to be a solution but I don't know what else to do. Any help appreciated

[rodbolt17]

its called prop walk,prop torque, and a few other names.
its due to the prop rotation in the water.
there is a steering friction adjustment.
sometimes a prop blade desighn change may help.
as the prop rotaes to the right it tends to pull the propshaft to the right as well.

[spinner1606]

Thanks for reply. I tighten the friction adjustment all the way but the pull is just to strong. I will look into a different prop.

[Doneaster]

I have a 9.9 Yamaha that also pulls to the right. It is quite severe if I let go of the tiller at WOT, it really has scared me because it almost caused my V-Hull Seanymph to turn over. I'll try some of the suggestions I've read on here and see it any of them helps and I'll post my results.

[madharchod]

mate its not the motor that's the problem its the boat if its a fiberglass boat sometimes they develop this center of gravity when in mould that they will never run straight we have nautiglass boat here in OZ that always run one side ie pulls to the right ,so you option is to down grade the motor to 6hp and no problem

[Bilge Rat]

Get the ventilation plate at least even with or 1" above the bottom of the boat.
Running it too deep will increase steering torque.

Is the motor trimmed so that the propshaft is parallel to the bottom.
If trimmed up too much, prop pointed up towards surface this will also increase steering torque.

[Doneaster]

I determined that the reason my boat is pulling to the right is because of a slight drag being caused by the Depth/Fish Finder transducer and a small patch on the starboard side of the keel.