Raw water pipes corroding?

[bobk]

The survey found the raw water discharge pipe attached to the port engine (6V92 TA 425HP) heat exchanger has signs of corrosion right at the bend. I also found a bit of paint bubbling and green scale below the paint in the same place on the starboard engine. They seem to be copper pipes and the broker suggested taking them to a radiator shop for braizing. Am I better off replacing these? I have no manuals to get part numbers. And where does one go for such parts?

Bob

[MikeP]

Don't consider brazing - Replace them. Brazing may fix the current leak but will not address the fact that large portions of the fitting most likely are much thinner than original. More areas of the pipe will fail soon. Replace them on both engines. Re brazing in general - I would also be concerned about galvanic corrosion between the copper pipe and the brazing material used for repair. I suspect there would be some interaction though I don't know for sure.

I don't know the part number but any DD dealer could supply them. I have found the local DD dealer in Ronkonkoma, NY

http://www.atlanticdda.com/locations.cfm

to be quite reasonable for replacement parts. N90 Injectors, for example, are $68 (exchange). I haven't seem there anywhere else at a lower price.

[Genesis]

Make sure the pipes really ARE corroding.

Its not uncommon at all to find people who have painted these have done it wrong. Specifically, you can't shove a painted pipe into a hose connection and not have the water eventually get UNDER the paint (between the paint and metal) and emerge somewhere down the pipe's length.

The part of the pipe that goes into the hose has to be UNpainted.

I'd strip off the paint and make sure you're really looking at a hole or weak spot. Sand it off and see if that's what's really going on.

[captddis]

The pipes are weird. I have had a couple that would ooze salt and blister the paint. When taken to the radiator shop, cleaned and pressure tested no leak shows up. Repaint and install and a few months later the ooze comes back.
If there is ooze or paint blistering, replace the tube. The ooze around hoses is not unusual and usually not a problem.
The discharge pipe is often some thing that Hatt made and not a DD part.

[Genesis]

Yep, they ooze and blister the paint because the paint extends under the hose! The water creeps under the paint and disbonds it, showing up somewhere along its length, and looks like a leak. ITS NOT!

Sand it off so that only METAL goes into the hose. The paint must start at or after the hose to pipe connection.

My engines did this and I thought I had all bad pipes. Nope - none were actually bad - the idiot who owned the boat before me pulled all the pipes and painted them to the ends, then reinstalled. Water crept under the paint and showed up further down, giving the appearance of a leak which was not actually there.

BTW, this will also stop the appearance of water/salt residue at the junction of the pipe and hose as well.....

[captddis]

If you reread what I posted, the ooze is in the CENTER of the pipes NO HOSES any where near!

[Genesis]

I know. Trust me on this; the water gets UNDER the paint and travels all the way down the pipe!

Try it - you've got nothing to lose. Sand off the paint where the ooze is and see if the metal is thin (you'll be able to poke right through it if so.) Rap on it with something small (don't hit it HARD, but rap on it.) If its perforating you gotta replace the pipe anyway, so there's no point in not finding out what's what.

If the metal appears sound then remove the pipe and sand off the paint to above where it enters the hose connection on either or both ends (depending on exactly how yours is set up.) Reinstall. See if your ooze goes away......

I ran into this on both of my engines and the pipes themselves were fine - the water was travelling down the pipe under the paint! I thought I was looking at replacing ALL of the pipes and as it turned out NONE of them were actually bad.

[bobk]

Karl, many thanks for your suggestion. The 'corroded' area seems solid. The paint does seem to go under the hose. I'll scrape it all down tomorrow and report back.

Bob

[bobk]

I know. Trust me on this; the water gets UNDER the paint and travels all the way down the pipe!

Try it - you've got nothing to lose. Sand off the paint where the ooze is and see if the metal is thin (you'll be able to poke right through it if so.) Rap on it with something small (don't hit it HARD, but rap on it.) If its perforating you gotta replace the pipe anyway, so there's no point in not finding out what's what.

If the metal appears sound then remove the pipe and sand off the paint to above where it enters the hose connection on either or both ends (depending on exactly how yours is set up.) Reinstall. See if your ooze goes away......

I ran into this on both of my engines and the pipes themselves were fine - the water was travelling down the pipe under the paint! I thought I was looking at replacing ALL of the pipes and as it turned out NONE of them were actually bad.

Karl, you are right on. I cleaned, scraped and tapped and then really rapped on the suspect pipes with a rigid putty knife--- they are absolutely solid. many thanks for more good advice.

Bob

[Captned]

I had a pipe (from the Water pump to the fuel cooler on 8v71's) completely go bad (turned pink and corroded / collapsed under the hose clamp connection and blew off while I was underway-"Hey, why is my high water alarm going off?") and I replaced it with hose I happened to have on board. Holding up fine. Why did they use pipes anyway? No drastic bend at this location...

Captned