Thru-hull leak

[Jotun]

This weekend after my boat was launched I noticed a tiny leak in the thu-hull for the engine raw-water intake. It seems to be coming from just under the thru-hull nut. I was thinking about tightening the nut a little but then I worried whether that would make the drip get worse. Should I try it and hope for the best or have the boat hauled back out and reaplce the thru-hull? It is the plastic type if it makes a difference.

[sailingdog]

Jotun-

Haul the boat and replace it... If you were to try and tighten it in the water, and the fitting is defective and it broke, you could sink the boat. You probably don't want to do that. Replace it with a Marelon one...which are the only non-metal through-hulls that are recommended for use. The non-Marelon plastic ones aren't durable enough...and effectively a waste of money IMHO.

[TrueBlue]

I also would do as SD suggests and haul the boat for replacement. If the flange is cracked, tightening a plastic fitting could make for a worse situation.

However, my opinion is that any plastic thru-hull below the water line should be replaced with bronze. If you're providing the labor for replacing just one fitting, the couple of extra dollars for bronze, is minor for the increased security in knowing you have a stronger component between the bilge and unforgiving ocean.

[sailingdog]

The reason I like Marelon is that the bronze fittings are subject to galvanic corrosion problems... I've seen them turn to copper sponge due to a bad shorepower cable in a marina in a month's time. Marelon is pretty well known, time-tested and accepted for use under the waterline.

[TrueBlue]

I used Marelon when installing an above waterline through-hull fitting on my last boat. The fitting seemed strong after installation, and acceptable for it's above water purpose.

But, compared to bronze threaded fittings, I simply could not accept the integrity of those plastic threads, secured solely by a plastic threaded nut. It seemed to me to be quite easy, by the use of overzealous torquing, to strip the treads.

IMO, the potential risks of galvanic corrosion affecting noble metals such as bronze, are much less than the potential of structural failure of plastic.

[Jotun]

The through hull there now is marelon and just above that is the raw water filter (also marelon, I think). If I go bronze wouldn't the filter also have to be bronze? I was thinking about upgrading the filter anyway, just not right now. But....

Also, I might have the marina do it. I'm thinking they can just put it up on the lift, do the work and then drop it back in pretty quickly. If my boat was sitting on their lift, I doubt they want me messing around with it, especially since it would probably take me twice as long. I'm still formulating my plan....

[pmoyer]

Let us know how it turns out. I'd offer to run down and help, but I have to be in the office today.... If you need me this evening (you're still on the Sassafrass, right?) PM me or something.

[Jotun]

Actually, I am in the office today too. The leak is very slow. A few droplets per hour. I am hoping to get it repaired some time this week. Thanks for the offer to help! I'll let you know if I need it.

[sailingdog]

If it's already a bronze through-hull, the problem could well be electrolysis. When the boat is out of the water, scratch it and if it is pinkish in color, then you have a problem.

[TrueBlue]

Originally Posted by Jotun

The through hull there now is marelon and just above that is the raw water filter (also marelon, I think). If I go bronze wouldn't the filter also have to be bronze? I was thinking about upgrading the filter anyway, just not right now. But....

Originally Posted by sailingdog

If it's already a bronze through-hull, the problem could well be electrolysis. When the boat is out of the water, scratch it and if it is pinkish in color, then you have a problem.

Jotun, the Marelon filter is separate from the Marelon through-hull. If you replace the through-hull with bronze, simply use the same rubber hose leading to the filter.