How to make my Yamaha 15 2stroke (Asia) drive in a straight line?

[andyalford]

My Yamaha 15 Enduro (2 stroke) motor does not want to drive straight. It's the Asian model with the gear lever on the side, unlike the US model.

This has driven me crazy for a long time. My previous Yamaha 15, also the Asia Enduro model, was fine. My new one (from Malaysia) requires a firm pull on the tiller to keep her straight. On long trips, the vibration and strain is quite wearing.

Same dinghy, so that is not the difference. Aluminium 3.1m Swift RIB with a nice solid transom and a reasonable V hull (aka Highfield.)

- I've tried mounting it off centre on the transom.
- I've looked for trim tab anodes, but can't find any - like I have installed before on a Tohatsu 8 which had a similar issue.
- I've changed the propeller, but probably the same Yamaha model.

Has anyone else had this problem and solved it?

[Privleoplag]

Missing the trim/anode completely?

[a64pilot]

Now that I think about it, I don't think my 20 HP Suzuki has a trim anode either.
If there is no trim anode and no place to mount one, your going to have to fabricate a trim tab.
Or try changing the tilt of the engine, sometimes that makes a difference

[Privilege]

Many outboards have a lever to stiffen the turning. It's often sticking out at the front of the engine under the cowl. On Yamaha's I think it is lower down at the top of the leg. You can stiffen the turning so that the boat stays in a straight line but make sure you're wearing your lanyard!

[hobopacket]

On my c22 with 6hp yammy had the same issue. Used the steer tightening to keep it in a straight line.

[Clipper4730]

We have an older 15hp Yamaha and it does have the trim anode. See if there is a place to screw one on, if so just get one online they are like $25usd. If not check the pitch of your prop. If it is high that could cause the turning moment trying a lower pitch might help.

[sony2000]

The foot has to be perpendicular to the water. If it is at angle, the trust from one side of the prop is greater than the other side. ie turn.
A four bladed prop should help a little.

[andyalford]

Originally Posted by sony2000

The foot has to be perpendicular to the water. If it is at angle, the trust from one side of the prop is greater than the other side. ie turn.
A four bladed prop should help a little.

Clever - I'll check that.

I agree with others that the trim angle has a lot of difference. I have mine fully deep, and the tiller pulls a lot more if it is in shallow mode.