Thru hull full of white stuff

[rwc]

Can someone tell me what the thru hull down in the right corner over the transducer is for?

It has strange white stuff covering it now. Trying to figure out what it is.

[rwc]

Chalky white stuff. Had completely blocked thru hull.

[Phillbo]

Probably your Macerator Pump thru hull.

[gigliotti63]

Very odd, it appears to be below your water line????

[rwc]

Oh yeah. Macerator pump makes sense. Also explains why it was totally plugged and I didn’t notice.

White stuff was on that one and the inlet for the head. Both brass (bronze?)

[mmwjr]

I cannot make it out on my iPad, can you get a closer in picture?

[rwc]

Here’s a closer photo. Pretty sure it is macerator based on the diagram in the 2009 manual.

That is it after pressure washing. Guy blasted it out.

Second photo is my two month old zinc with over 50% wastage. I think the build up must be from the bronze acting as a cathode.

[Phillbo]

That zinc is only 2 months old? I assume salt water based on your location. I'm a fresh water boater so no clue if that is an issue or typical wastage in salt.

[rwc]

Yes, salt. I can't imagine it is normal. I'd have to pull the boat and change the zincs every few months! I should only have to change them once a year, and even then, should only be maybe 50% worn.

Something is wrong, either with my boat sending out electricity or one near me, I'm pretty sure. I found some stuff on the interwebz about people having rapid zinc wastage and chalky build up on props/shafts. Turned out they had a misplaced grounding wire.

Looks like I'm going hunting for stray currents, but until I find one, I'm blaming the grungy old sail boat beside me. All was fine until he came along...

[mmwjr]

It the thru hull bonded inside?

Either you, the marina, or a neighboring boat has a serious stray current issue.

Anybody near you having similar issues?

[rwc]

Going to check. I just read the West Marine article about testing through hulls, so will check that as soon as she is back in the water. I’ll look for sources on my boat first. My neighbor had some electrical trouble, but hasn’t mentioned any zinc wastage. I’ll ask him.

I’m guessing it’s either me or that sailboat. My electrical looks questionable. My battery cables are something like 3/0 which is random, heavy and weird. They must have either been salvaged or cost an absolute fortune. I could probably sell them for scrap copper and buy a new boat.

There’s a workboat with survey eqmt onboard two slips over that could be a culprit as well.

[dannyrayz]

How long have you had the boat? Consistently changing the anodes? New boat to you? Be sure correct anodes are installed for the type of water you moore in. Zinc, alum or mag. White deposits look like calcium, crustation poop.

[shrew]

If the 'stuff' in the through hull is inside of the hole, it looks like a means to close off the through hull. If it is around the flange, it looks like a bedding compound or caulk of some kind.

A few things to keep in mind...

1) Any below-water through-hull should have a seacock on the inside. (Does Yours?)

2) Below water through hulls should be Bronze or Marelon. That through hull looks like Nylon.

3) You can follow the through hull on the inside to trace where the hose goes.

If there is no hose and no seackock, that needs to be fixed.

The zincs can be made of three materials, which are dictated by the type of environment they are in.

Zinc: Saltwater (only)
Magnesium: Freshwater (only)
Aluminum: Salt or Brackish water

The zinc is corroding because it is doing its job. IT is a sacrificial anode, meaning it will take the hit from stray current before you aluminum drive or trim tabs do. You have stray current either in the marina or the boat itself.

[Phillbo]

Do not swim in your marina.

[rwc]

Originally Posted by Phillbo

Do not swim in your marina.

For real this time!

Thru-hull is bronze, bonded, comes from the macerator and has a seacock (was open, now closed as I'll almost certainly never use it). Ground wire runs to the back of the engine and appears to be in good shape.

The white stuff wasn't there two months ago when the boat was out of the water, so it's definitely not supposed to be there.

The zincs are doing what they are supposed to do, just way faster than they are supposed to do it ( I assume). I bought the boat in September and between September and April saw way less wastage than I have from April to now.

I have one other bronze thru-hull that does not have a grounding wire. Assume it should?

[Phillbo]

You need to bring this to the attention of your marina management. They need to identify the problem.

[rwc]

Originally Posted by Phillbo

You need to bring this to the attention of your marina management. They need to identify the problem.

You are right.

I want to confirm it's not me first though!