3870 trim tabs question-gctid811717

[Smitty]

I have my boat out of the water right now to paint the bottom and other chores.

I think my boat would be the same as other 1986 3870's, but the way my 4 tabs work seems strange to me.

I am rebedding all the transom bolts screws etc and pulled down on the outside port tab and when I pulled it down the port inside tab went up.

Tried the same excercise on the starboard tabs with same result...... can this be right?

I usually run at 7 knots, so assume I am not using any tab when I put the tabs up with the controller, but obviously only the outside tabs are up.

What am I missing here?

[smitty477]

"and pulled down on the outside port tab and when I pulled it down the port inside tab went up.

Tried the same excercise on the starboard tabs with same result...... can this be right?"

Yes - it is fine.

[drewhaas]

To elaborate- my understanding is that by pulling down on one tab you're taking fluid out of the cylinder for the other tab rather than using the hydraulic pressure created by the tab motor. It's why tab systems need a reservoir.

[Smitty]

Thank you....you guys are really helpful

[Tabman]

Yup, that will happen on the two tabs on the same side since they are teed together. Both Tabs will come up when all the fluid is removed from that side by the pump.

Tom