RE: Outboard motor pulls to the right

Question
Ron-
I read an answer you posted for a fellow whose fiberglass boat pulled very hard, however- i have a 25 hp mercury outboard on a 15ft aluminum john boat that pulls very hard the same way.  the motor is a tiller handle, and when i am driving the boat the tiller pulls very hard to my left...meaning if i let go of the tiller the boat would make a sharp right turn.
I have adjusted and replace the trim tab as well as the prop.  I believe its possible that the prop shaft may be a bit beant.  What should i do to fix the motor from pulling so hard?

Answer
Hi Spencer...Thank you for selecting the undersigned to reply to your question. By the way, I'm not a mechanic.

First of all, a bent prop shaft will not cause your boat to steer in the wrong direction, but it will cause your engine to vibrate, and if the damage is severe enough, you'll notice an oil slick emanating from a broken prop shaft seal and/or a fractured lower gear case housing.

When you check the capacity plate, likely on the inside of the transom, you might find your 25hp motor exceeds the recommended maximum hp for the design of your 15' boat, which has a flat bottom. Also, make sure the cavitation plate is even with the bottom of the hull, and if not, make the appropriate adjustment.  

Since your boat veers starboard or to the right, which is likely the side you're sitting on, your weight could be the influencing factor. Uneven weight distribution of fuel, equipment, etc. might be another issue. Perhaps the pivot tension of the engine is too loose and should be tightened. Usually, turning the trim tab toward the opposite direction to which the boat veers often solves the problem. On the other hand, maybe you have an oversize prop and the torsion created by its left hand rotation is affecting steering.

If you haven't been successful after applying the above, best you consult a reliable and qualified marine mechanic.

Safe Boating
Ron