TRS I/O steering problem

Question
Dear Mr. Blanchet:
I am new to boating, I have a 1977 Fiberform flybridge cruiser with dual steering stations. The engine is a Mercruiser 350 (260hp rated)with a TRS outdrive.
Problem: I need to constantly correct course. The boat is constantly drifting left to right and back again. I cannot keep a straight heading. do you have any ideas on what the problem could be? Thanks, Chris

Answer
Hi Chris...Thanks for selecting the undersigned to reply to your question.

Next time the boat is hauled out of the water check the alignment of the keel. If it's wavy, the backbone of the hull has deteriorated beyond reasonable cost to repair.

On the other hand, new boaters may not realize that wind direction/speed, force of current, and effects from waves, also cause a boat to drift side to side.

Also, there's a small adjustable fin underneath the cavitation plate on each outdrive, which is where the upper and lower housings join. The fin may require adjustment to resolve the symptoms you have described. The best way to determine whether this may be the problem, is to find calm water (no wind-no current), and at various speeds, take your hands off the steering wheel. In the event the boat veers to port, the fin needs adjustment to starboard and vice versa. Check this out first. When properly adjusted, the boat should maintain a straight course with little guidance from you.

In the final analysis, you might consider retaining a qualified marine surveyor to determine the cause of the drifting situation.

Safe Boating
Ron