[fishrdan]

Is a bronze thru-hull fitting going to cause any problems on a painted aluminum hull, (galvanic corrosion)?

I need to replace the livewell drain thru-hull fitting on my project boat and wanted something more sturdy than the original plastic fitting, IE: if this fitting were to fail it could sink the boat. I'm under the impression the manufacturer used plastic fittings because are were less expensive, but unsure if they did it to avoid corrosion problems between dissimilar metals. The bronze fitting won't be in contact with aluminum since the aluminum is painted and I'll be sealing it with 3M 5200.

My main concern is to avoid galvanic corrosion. I just sanded/painted the edge of the transom getting rid of crevice corrosion along the corner of the transom-hull and don't want to invite another problem.

[dingbat]

Any time you have dissimilar metals even in proximity of each other there are bound to be problems.

Don't confuse the cheap PVC thru hulls with some of the better composite materials. I would use a Marelon fitting and not worry about it.

[fishrdan]

Thanks dingbat, those Marelon fittings sound stronger (glass reinforced) than the original nylon fitting that was on there. I'll have to get one of those for peace of mind on strength and corrosion.

Since you brought up PVC, I think my concern for this fitting shouldn't really be an issue since the livewell pump is made out of PVC and if anything is going to easily snap off, it's going to be the thru-hull pump and not the thru-hull drain.

[Ned L]

Not to change your direction at all, but as an FYI, all that is needed to properly use a bronze through hull on aluminum would be isolation washers, could be as basic as disks cut from a plastic milk jug. (you are onto the right idea thinking that the aluminum is painted, but in reality the paint would probably get scratched through during tightning. Likewise, 5200 would also allow metal to metal at some spot.)