What causes a boat to not keep in a straight line @ 6 knots

[desertislander]

I managed to get out yesterday and tried a few different things as suggested. Firstly, I was almost on high tide and there was very little chop, in fact quite calm so that seemed to make a difference although it was still doing it but not so badly. I then found that if I just trimming it up as previously suggested that seemed to virtually cure it!! So it does seem that weather and current are major factors and I think now with a bit more practice and trialing I should get on top of this

[Noelm]

Good stuff, just try a bit of weight in the back as well, and more trim, do the very easy, no cost things first.

[FNQBoat]

I'm new to boat owning, just got an old seafarer venus with 75hp evinrude. She goes ok but veers to the right when not holding the steering wheel. not an issue really cause im always holding the steering wheel but i'm a bit anal about things being correct. not much knowledge of the forward controls make up. How do i figure out where the issue is and which components i need to replace. Is there a "forward controls guide for dummies" anywhere i can read up on? Want to slowly start upgrading the older parts of the boat. needs a new steering wheel anyway because it looks ratty but i want to figure out whats causing the veering. helm pump?

[Bremic]

How much does it veer off course? They never run true the way that a car will on a straight road. The prop torque will cause it to slowly turn to one side.

There is a trim tab just above the prop that can be nudged left or right to provide a small rudder affect. A small nudge to the left should improve things, but they are never a set and forget when driving them.

[Dignity]

I managed to get out yesterday and tried a few different things as suggested. Firstly, I was almost on high tide and there was very little chop, in fact quite calm so that seemed to make a difference although it was still doing it but not so badly. I then found that if I just trimming it up as previously suggested that seemed to virtually cure it!! So it does seem that weather and current are major factors and I think now with a bit more practice and trialing I should get on top of this

I don't think enough people play with their trim tilt even at speed, ive been on too many boats where once on yhe go the motor goes down asbfar as possible and stays there. Once I got trim tabs I too stopped using the trim tilt much but I have been paying a lot more attention to it in the last year and have found I can pick some extra revs, speed with a corresponding drop in fuel consumption. It's not huge but it all adds up.

[Fed]

NECROPOSTERS....Someone get gun!

[gofishin]

... A small nudge to the left should improve things, but they are never a set and forget when driving them.

Actually the trailing edge of the steering tab needs to be moved to the right/STB. This kicks the O/B over to the port hence will help correct the problem.
Cheers
Brendon