When I was running my boat yesterday I have noticed the the boat pulls to port slightly. The boat is a 79 30' Scarab with counter rotating TRS drives. The tachs are new and according to them they were running the same rpm, and I could tell by the hum from them. I tried trimming each drive up and down to see if it had an effect and no change. The props have not been changed and are 24" hydromotives 4 blades. The boat rides level and with 2 people in it. It has an external tie bar and the heim joins are in good shape. I have not checked the toe in, but wondered it that could cause it? If I let go of the the steering wheel, the boat will slowly start to turn the drives to make a turn to port. This also happens at low speed. If I have both engines at idle in forward, and let go of the wheel, the boat will start to turn to port. And even if I bump up the port engine speed over the starboard, it does the same thing. What other things can I check.

Internal or external steering? I had a bad seal in one of my steering rams and my boat would also drift to the port side. It was leaking by the ram and would slowly turn the drives. I guess you could let it idle on the hose and see if the drives move.

Its internal stock type steering. A push pull cable acting on the Saginaw valve. Ill have to try that letting the engine with the PS pump run and see if it pushes the drives over. Maybe a leak in the hydraulic ram attached to the tiller arm?

1) the Centerpoint on the Saginaw valve is adjustable
2) the drives have torque tabs. On a counter rotating twin most guts cut those off flush with the plate. If you're still running em, make sure they are aimed straight.

My vote is #1. Saginaw valve needs adjusted OR cleaned, lubed AND adjusted.