Starts in gear, sort of. Vacuum at filler.

[DukeSwanky]

Mine is a 1989 28-foot Coastal with twin 350 cubic inch, 260-horse engines. Port engine starts in forward gear, sort of. The shaft turns but slowly. If I shift into reverse for just a second after start up the shaft stops turning and the transmission is in neutral. When I pull the fill plug to check the fluid level it releases a vacuum with a sucking sound. I note there is a small "vent" with spring-loaded cap on the transmission. Is this to let it "breathe"? Is this vent clogged? How to clean it? Replace it? Thank you all in advance for whatever guidance you may provide.

[Billm]

Sounds like a shift cable adjustment. Look on the side of the transmission where the cable is attached. There is a lever there with three little holes. One for forward, neutral and reverse. Now there is a little ball on the transmission itself that is supposed to pop into one of the three holes. That ball may be frozen, it needs to be free to pop in and out of one of the holes. When you move the shift lever at the helm, you should be able to feel that pop into neutral. When you push the shift control all the way either in forward or reverse, the ball needs to be fully popped into one of the outer holes. There is no such thing as being slightly in or out gear. Make the necessary adjustment to the control. My transmission sometimes releases a little pressure when I unscrew the plug. Hasn’t seemed to be a problem for me.

[CptBill]

I will add if your getting a large amount of pressure it would not hurt to clean the vent just to be sure

[DukeSwanky]

Source of the post I will add if your getting a large amount of pressure it would not hurt to clean the vent just to be sure

How do you clean the vent? TIA.

[Billm]

The vents are cheap and easily changed. But first I would discuss your situation with a mechanic trained on the BW transmission. You may need to have the fluid changed and the internal screen cleaned.