When I worked on RC boats I would install something that looked like a backward facing water pickup, then ran a loop of tubing above the waterline and then to the bottom of the bilge. Once moving, water rushing by the tube would create a negative pressure behind it and it would suck the bilge dry. Seems like this would be a no brainer for a big boat. You may have to play with the height of the loop to keep water from coming in when you back down, but that should be a matter of testing, or maybe a simple check valve. Is this not worth it, somehow risky? Seems you could put the tube right at the bottom of the bilge and not have that leftover water that the pump always leaves because of its height.

Thanks, Randy

Mermaid Marine makes such a critter for sucking the condensation out of your drain pan for AC units. It simply goes into the water inlet hose and has a smaller hose that goes to the drain pan. Whenever the AC pump is on and pushing water thru the system, the gadget is sucking the drain water out and discharges it out with the water supply. I have 1 in each of my boats and they work great. Bought 1, took notes of it, made several more with improvements. Would just require a little bypass plumbing to install in your motors water hoses.

Mermaid Condensator

I would be worried about a syphon and the boat filling with water and not knowing its a problem. No chance of that with the hose above the water line.

You shouldn't be getting that much water in the bilge. Something would be wrong. Lol

Thanks for the replies. Never thought about a siphon, good point. Would be neat to incorporate it like US1 described. Going to have to wait until my next I/O boat.

not a new idea. I don't remember the brand, but 30+ years ago I saw a syphon setup in an old at the time aluminum fishing boat. It was basically a small backwards facing "scoop" with a u tube above it .The tube went straight up well above the water line then back down to bilge. It appeared to have come that way from the manufacturer. I thought it was a cool idea. With a boat of any size that doesn't leak, why would it be needed. The one I saw was in a riveted boat that was prone to leaking. Some pwc use a syphon setup on pump outlet ...

Some PWCs had/have them since the late 1990s. They would use the force of the water in the tunnel rushing by to pull water out of a tube/pickup in the bottom of the hull which had a one way valve in it.

Some of used these "duckbills" in PWC racing back in the day as well. You would replace the hull drain plugs with them.

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I actually installed a duckbill inside the bilge on my old Sonic. The Sonic had PVC tubes from the bilge to the bow. IF there was water in the bilge, and the boat was tilted nose down as in while towing or parked on the trailer; the water would migrate forward and create a stale water smell problem. The duckbill worked perfectly to only allow water to drain front to back.

Duplicate

This was standard equipment on Lyman boats of the past. My wooden 23 Lyman has exactly this setup. A loop of 3/4" copper tube with one end attached to a rear facing opening developing suction as the water flows by and the other end in the bilge, just off the bottom. Works still. If I get close while underway I can hear it sucking. Wood boats leak a lot so nice to have.