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Heat Exchangers Longer Life or Replacement

knuckle47

Advanced Contributor
"Always something, as they say

"Always something, as they say. During a recent oil change, my brother informs me that the raw water intake connection on the port exchanger has a slight drip. It appears to be at the junction of the hose barb and the main outer tank. Last year I had to re-solder this union on both heat exchangers for the same problem. As if the weight of the hose from the manifolds is stressing the joint. Does any think that this may be an impending sign of the need to replace them since this happened last year or just fix the joint again and shut up about it...?

Internally they are clean and have been flawless in performance. I have reamed them with a plastic rod and replaced the end caps and gaskets. The bronze end caps are bullet proof and probably 1/8" thick but the "barb" extension that the raw water hose attaches to, just always seemed to be so thin. I can surely just drain them a solder it....what bugs me is that I did a darn good job last year when I repaired it and what is maybe 125 hours later ( 10 months of NJ seasonal use and non-use)it is dripping again...

Could it be due to galvanic corrosion? I mean...is plumbing solder like zinc and gets eaten up during the process? Just in case, I do watch ALL of the zincs on the boat and they do get changed about 3 times during the active season and the boat is on the hard from Nov to April... Al"
 
"Al,
If you are changing your


"Al,
If you are changing your zinks 3 times in the season it sounds like you have a bigger problem just in that. Unless I am wrong and I have been before, that is not normal."
 
"Hi Paul,

I should have exp


"Hi Paul,

I should have explained....I am changing them as a routine 30 day wear item..NEEDED OR NOT ! Only the u-coolers and heat exchangers. The rest on the shafts, rudders and trim tabs are fine and do last thru the 4-5 months in the water. I know from past experience that the breakway particles can clog those little honeycomb cores in the coolers and exchangers so I do try and keep them from just crumbling away. So since it is so easy to just unscrew those 4 pieces before they jam up inside those holes and break off, I just do it."
 
Might try a dremel tool wire b

Might try a dremel tool wire brush and JB weld. Although the purist will reject the idea of epoxy on a soldered joint. The lower body of the heat exchanger is quite thick and really demands a lot of temp/heat for a decent sweated joint.
 
"Dave, Your'e right...I te

"Dave, Your'e right...I tend to believe I can do a decent job on that sweated joint, I can't see how the JB Weld would hold...MAYBE as an emergency thing but I would prefer to sweat it again. I use that yellow MAP gas cylinder..it gets things hot quickly so I do get a good flow of the solder...I do like your idea about cleaning it with the Dremel tool though. I had used a wire toothbrush last time with the heat applied and maybe it was still dirty below. Funny , I think back to last year and there actually may have been some JB Weld on it as when the heat was applied, something did crumble off.

My bigger concern might be the possibility of solder being reactive to the galvanic system.

BTW: How did your transmission finally work out...Never read that much about it. This place is like walking into the marina, you get to "hear" several different things from people."
 
"Al:

One of my galvanic act


"Al:

One of my galvanic activity tables shows tin-lead solder being more active than brass and copper so it is a possiblilty. If you want to eliminate this, clean it up real good and use silver solder. (think oil cooler and the acid trick plus that wire wheel in the dremel - use a stainless wheel if available.)

I'd guess if it is a corrosion issue, you'd see the same issue on the oil coolers as I'm sure they received the same solder last year.

Last thought would be to take a scribe and probe around the barb-tank joint to make sure the barb's wall is still solid - no weak (thin) spots. If you need that barb, I have a carcass HX I could extract it from if the local radiator shop doesn't have one.

ps- saw the "grey beard" confirmation on the plug change - one less item on the worry list."
 
"Hi Al; on that starboard tra

"Hi Al; on that starboard transmission. It seems to be stable, but does rotate at about 1 rev per second in neutral. I had done about 4 changes of fluid and the water is MOSTLY out. Its done a bahamas round trip since the incident, and maybe 25 hours total since then. It's on the list for this fall/winter; it all needs to come out anyway for the sandblasting/priming/painting every decade... Luckily, i have a 2000# davit at the house, so I can do everything myself."
 
"One more comment on the solde

"One more comment on the soldering of the HE. I've learned the hard way with sweating very thin metals (hose barb) against very thick metals (copper pipe). It's not too hard to flame a hole in the hose barb, even with MAPP. Its that serious chuck of copper pipe that needs 99% of the heat, the barb will heat to temp in maybe 5 seconds. I recall trying to resweat the end cap mounting spider one time. I believe most every fitting fell off the HE before that pipe finally gave up the one fitting I was trying to remove. Maybe acetylene is the better process. I notice most plumbers use the hotter gas on copper tubes, but they have a practiced hand too!"
 
"Hey you guys are terrific. T

"Hey you guys are terrific. This bugged me so today I went to the boat and started it up.... First, it is not raw water ..it is coolant. NOW I know why the recovery bottle is a little bit lower !

It turns out the "barb" or tank has no crack but apparantly the tangent where the two circles come together ( one from the hole cut into the coolant portion of the tank and the other being the circumference of the hose barb fitting)is where the leak is. As suspected the "weight" of the 1 1/4" hose places a bit of downward pull pressure as it passes from the top of the manifold towards the bell housing type mounting of the heat exchanger. This 1 inch arc leak is simply a result of a separating of the solder at the very top of the tangent, between 11 and 1 o'clock.

Although not my prettiest solder joint, I was able to remove the hose...lose about 3 cups of coolant into a pan as a result keep the area dry and hot enough to make it work in place without have to disassemble the whole thing...Seems like it is a good idea for the future to build up a fillet of sorts to provide a bit of strength to that spot. The silver solder is a great idea for the strength alone. Nice to know the solder is NOT YET being eaten away
as you are right Mark....it is the same solder"
 
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