Mercruiser 7.4L heat exchanger repair

[Eastboundndown]

Hello everyone, I’m a new owner of a straight inboard boat equipped with a fresh water cooling system. Yesterday I had my starboard engine start overheating so I shut it down and limped in on port. I just located what I hope is the only problem with cooling system. One of the copper 90 degree hose fittings on fresh water side of heat exchanger is physically loose. No antifreeze left in system so I’m guessing it was all pissing out at that elbow. I have done a decent amount of soldering copper pipes before the industry changed to pex and crimp. I guess what I’m asking is can the fitting be removed and replaced in the same manner as residential plumbing or is that wishful thinking and I should try to find a radiator shop to do it. If those even exist anymore. I would really prefer to have it fixed by brazing/soldering then try using some type of epoxy. Any helpful input is appreciated. Thx

 

[Bondo]

or is that wishful thinking and I should try to find a radiator shop to do it.

Yes,... to much heat in the wrong place could cause more damage than you need or want,.....

 

[Scott Danforth]

Is this a CHAMP or monitor heat exchanger?

I would recommend that you take it to a radiator shop so they can pressure test after the repair

the tube bundle is brazed, so that is not an issue, and the elbows to shell brazing is usually done prior to the tube bundle being installed in the shell and the ends soldered on.

the issue is if you add too much heat repairing the elbow, you can develop a leak where the shell and the double tube sheet come together. This is where the pressure testing is needed

a good mapp/oxy torch is needed to get enough heat (propane wont cut it) if you attempt a solder repair

a a good brazing tip on an acc/oxy torch is needed if you attempt a brazing repair

you have to work fast, and cool things behind you

 

[Eastboundndown]

Thx guys, I can sand flux and neatly solder copper pipes but this sounds like it might b above my pay grade. I’m an electrician by trade but I have a few good HVAC techs that I work with. I know they have to braise condenser lines so is this something I should ask them to help me with. I’m still a little unclear on if the hose fitting needs to be braised or soldered. It appears to me(again an electrician) that the fresh water cylinder where elbow needs repair is separate from the larger salt water cylinder that has all the little tubes in it. I would take a few pictures but I don’t know how to post them on here.

 

[Eastboundndown]

Is this a CHAMP or monitor heat exchanger?

I would recommend that you take it to a radiator shop so they can pressure test after the repair

the tube bundle is brazed, so that is not an issue, and the elbows to shell brazing is usually done prior to the tube bundle being installed in the shell and the ends soldered on.

the issue is if you add too much heat repairing the elbow, you can develop a leak where the shell and the double tube sheet come together. This is where the pressure testing is needed

a good mapp/oxy torch is needed to get enough heat (propane wont cut it) if you attempt a solder repair

a a good brazing tip on an acc/oxy torch is needed if you attempt a brazing repair

you have to work fast, and cool things behind you

I’m sorry but I don’t know what champ or monitor system is referring to. It’s a mercool heat exchanger on 7.4L mercruiser engine with thunderbolt ignition. Does that help.?

 

[Scott Danforth]

the whole thing is made of copper tubing, sheet and bronze castings. there is a mix of brazed and soldered bits

the elbows are standard nibco elbows that are coped to fit the shell (should be 5.125 or 6.125" OD. and there is a hose retention bead rolled in it.

the shell is just copper tube, cold sawn to length.

the tube bundle is brazed together, and dropped into the semi-brazed shell.

you can repair with solder, however as stated prior, you need to pressure test because you may need to repair something that you damage.

the industrial radiator guys have experience on these.

I worked for Champ and can repair heat exchangers myself. then again, I made some on the line as part of my training. However I would just call the plant manager and have him run it thru their repair line

 

[Scott Danforth]

Mr Cool is an aftermarket unit. the factory units came from Champ and Monitor.

not sure how the aftermarket unit is made.

 

[cyclops222]

Remember a lot of pro places ....CHARGE EXTRA..... if you bring in a damaged repair attempt.