Trojan Boat Forum

I have a rear bilge pump, a rule 500 (?) on my F26, near the rudder, and it discharges through the hull right above the boot stripe on the transom. The discharge hose loops upward a foot or so above the discharge fitting and then back down to the thru hull fitting.

Is the thru hull too low? Is there a risk of a reverse siphon if the stern squats too low, say the thru hull is underwater and the pump cycles on and off leaving the hose full of water. Should I move the discharge higher on the transom and if so, how best to plug the existing hole/fitting without trying to fiberglass the transom? Or how about a one way valve?
Oh and my boat is already a little tail heavy and squats considerably ( the 454 probably contributes to this) and with 4 divers and gear the discharge is at or under water.

foofer b wrote:I have a rear bilge pump, a rule 500 (?) on my F26, near the rudder, and it discharges through the hull right above the boot stripe on the transom. The discharge hose loops upward a foot or so above the discharge fitting and then back down to the thru hull fitting.

That is what protects your concern. the pump won't suck thru the discharge hose. If it really ends up underwater then you should lift it higher, just punch another hole and fill/block off the old one.

It would only siphon back if the outlet was under water and the pump quit work when th line was full of water most of the time the pump will suck air before cuting off braking any siphon . the rasied loop helps. water would have to be above the loop for it to come back in if it gets that high you need more the that pump. with That said it would better off higher but the higher it is the less flow you will get from the pump

I have a F-28 and my bilge drain hose is set up the same way. With weight the thru-hull migt be underwater, but when you are underway it's way out of the water. I have no problems with mine.

leave that where it is Paul's right the loop will stop the water from coming in. But I'd put in a 2nd pump and mount the switch for it higher than the other and put in another hole for it. Pump size I'd go 2000 gal an hour.

The hose can siphon if the water on the inside is lower than the outside. Now the question. If the pump sucks air will it pump that air outside? I guess it could pump enough to put air in the line and break a siphon. That is a interesting thought.

That's a thought. And a good reason for that 2nd pump and switch.