Relocate Bilge Thru Hull?

Yakmandu · Posted: Sat Oct 19, 2019 7:50 pm Post subject: Relocate Bilge Thru Hull?

I have noticed that the outlet for my bilge pump is sitting at water level. I added a kicker motor and a second house battery since I bought the boat. I also have a 70 quart cooler that sits near the transom.

The last time I launched the boat on a steep ramp I got 5+ gallons in the back of the boat. The river water was pretty dirty so I could see it didn’t come over the rear splash well. The bilge outlet was well below water level during launch. I can only surmise that the water siphoned back through the bilge pump. Under normal operation, the boat is always bone dry.

Would it be best to move the bilge outlet higher on gunnel? Or, do you think the bilge pump is the issue?

If the consensus is to relocate the bilge outlet, is there a fitting that will close off the exiting outlet, or is fiberglass repair in my future?

I have a 2005 19 Angler with a 90 hp Honda.

Thanks for any help or recommendations.

thataway · Posted: Sat Oct 19, 2019 8:37 pm Post subject:

The bilge pump thru hull out let should be above the waterline. There is (or should be) a "loop" in the discharge hose, which comes up much higher, and thus keep water from coming into the boat. However, it is possible it could back siphon.

One likes to keep the "head pressure" that the bilge pump works against as low as possible, because the impeller pump is not that efficient when working against a high back pressure. Also the "corrugated" hose is not the best--and it is subject to breaking as it ages--which is a possibility in your case also since your boat is 13 or 14 years old. I would check out the hose, and consider replacing it with a high quality smooth bore---and get the loop up so no water can back siphon.

It is best to glass over the thru hull (properly). At least one of the 25's had the scuppers too low, and those who moved them up, did have hull repair done. You can leave the thru hull in place, and then "cap" it. I don't know what the inside of the thru hull is like--ideally it has a sea cock on it--but I doubt that it does. The next best, would be that the tail piece is threaded into the thru hull, and you can put a cap on the pipe. IF hose, is the only alternative--some have put either solid metal, wood or plastic plugs in a piece of high pressure tubing or hose (not the correlated tube which comes with the boat), and double hose clamp it. (All thru hulls should be double clamped if possible.)

Micahbigsur@msn.com · Posted: Sun Oct 20, 2019 12:43 am Post subject:

I have used 1/8 thick round bronze plates inside and out with a bronze countersunk machine bolt and 5200. Very functional and safe but a visable solution.

BrentB · Posted: Sun Oct 20, 2019 8:16 am Post subject:

One possibility is over weight

Micahbigsur@msn.com · Posted: Sun Oct 20, 2019 9:48 am Post subject:

The plates that cover a 1.5" opening weigh about a pound or less each. They take about 5 minutes to install. They are made in another 5 minutes with a drill press and a sharp hole saw. Amazon has the bronze countersunk bolts. The bronze must be 90% copper (architectural bronze), equivalent, or silicon bronze. Brass has to much zinc and will suffer from dezincafaction. The inside plate can be square.

Yakmandu · Posted: Sun Oct 20, 2019 9:57 pm Post subject:

Thanks for the suggestions. I will first replace my bilge pump hose and do some testing. That sounds like a good place to start, especially with a fifteen year old boat. I wish I had thought of it when I replaced all my fuel lines and fuel tanks!

I’m sure I will raise the outlet a few inches when it’s all said and done. That would really help!

I’m sure my boat is a little stern heavy. Being only 19 feet, there isn’t a lot of “boat” up front to spread the load. Since I travel solo, I know I’m not overloaded. Heck, I’m barely a buck sixty myself, so I know it isn’t a “personal” problem!

Thanks again!