Thinking about putting in brass raw water pickups on my 27' Comet (lost one of the aluminum grates) Should i completely isolate them ot am i over thinking it? Thanks G
Steel hull, aluminum,wood, fiberglass? Fresh water, brackish, or salt? Are they really "brass" or another alloy such as bronze? Too many unknowns for anyone to give you an answer worth reading.
I agree with Marmot. But what ever material your boat is made of, make sure your metal thru hulls are bronze. Brass is household stuff which can rapidly fail, and put your boat right on the sea bottom.
Yikes Sorry got in a hurry at lunch, they are a cast bronze Apollo raw water pickup, the boat is an Aluminum hulled Custom 27' Comet used on the Great lakes but wouldn't think water would be the problem its the dissimular metals I'm worried about firgured I would have to barrier coat the bottom and bond them at least, anyone have any expierence with doing this? Thanks G
When water gets near a boat it is called an electrolyte so the flavor of the water is very important as that is what starts fights between dissimilar metals. In my opinion, the best option is to weld and aluminum inlet to the aluminum hull. Second best is to use a Marlon fitting if a suitable one is available. The third best is to use a stainless steel fitting with isolation washers and do not electrically bond it to the hull. Be prepared to pull the fitting the first time the boat is hauled and depending on how well it is working (electrochemically), every year or two after that. My last choice would be to do the same with a bronze fitting. A bonded bronze fitting in an aluminum hull with DC electrical leaks and a wet bilge can go away in days in anything other than distilled water.
Best way to go is with aluminum or marelon. The best setup is to weld an aluminum through hull into place. 5086 is the preferred material. If you go with bronze then do not bond them. You will create a circuit in the water with the bond. Marinette boats were built with isolation between any non-aluminum parts and the hull. They used bronze through hulls that were isolated from the hull completely. There were even plastic spacers on the shaft couplings to prevent metal to metal contact. To verify the isolation you would ground the shaft while monitoring the CAPAC meter to see that it deflected downwards.
Good stuff guys, still deciding which way to go but i did find an aluminum strainer i liked, removable so i can barrier coat it, that was the problem with the old welded on one.. http://www.pyacht.com/groco-sc-slotted-strainers.htm Have a good holiday all. Thanks G
Hi, When I first saw this I like a few others thought it was the thru hulls you were asking about not the scoops on the outside. If you are going to screw one on use Titanium Screws if you can - you will have much more chance of undoing them in the future than using SS in Alu.
When my boat was in the yard, I had Marelon fittings installed for the sewage and air conditioning systems. The original bronze fittings for the engine and generators are on aluminum risers with a dielectric insulator between them and the bronze. I'm planning on yarding the boat this fall/winter and doing the bottom. While it's on land, I'll pull the sea suctions, inspect the aluminum and replace the insulators. I'm having quite a time finding who makes and stocks these insulators, they are a female nipple with an insulation dielectric inside a steel shell. Jim Bauer
