Trim pump vent screw

[rb1980]

Just finished replacing my trim lines and bleeding the system. (for a novice, seemed to go off without a hitch). One thing the service manual is unclear on is what you're supposed to do with the vent screw. (I have older `74 "large reservoir black pump"). Once I'm confident all the air is out of the system should I tighten up and close the vent screw, or leave it open slightly?

 

[ziggy]

Re: Trim pump vent screw

i don't know the answer to your question other than. i can't image a screw being left slightly unscrewed on a boat. it'd vibrate off and fall in the bilge, in short order i'd think..

 

[Alumarine]

Re: Trim pump vent screw

I'm wondering if it's just a "vent" when you are filling the resevoir?

Hopefully someone who knows will come by.

 

[rb1980]

Re: Trim pump vent screw

Looking back it seems like common sense, but the only reason I asked really, is that the screw was already kinda loose when I started the job.
My intuition tells me the vent opening is only for when filling the reservoir to prevent positive pressure building up when using a tight fitting fill nozzle. I used a small pump oil can with flexible nozzle and just let it kind of drip in there so probably did not really even need the vent.
I went ahead and tightened it down and everything's still working fine. The only reason I could think of to have a vent under normal circumstances is to prevent a suction in the reservoir.

 

[picklenjim]

Re: Trim pump vent screw

Yes tighten it when finished.It's just so if you use a funnel in that small fill hole and it blocks off completely it wont make pressure in the reservoir and stop filling.