Just seeking opinions on the corrosion on the heat exchanger. Is is to severe to be usable again or is there some solution to repair it.

Took it around to a local engineering firm here in Wynnum, the owner told me he did his apprenticeship refurbishing heat exchanger's, that was a good start to the discussion, he didn't seem phased by the damage so going to get it refurbished by welding and re machining the sealing faces removing old rusted studs, new welsh plugs and just a general clean up. I will post a pic when its done.

Looks like you got onto the heat exchanger just in the nick of time & the rest of the cooling system for that matter. It pays to keep a close eye on the engine / raw water anodes. I get about a year out of the heat exchanger ones but the one in the Detroit raw water pump was completely gone, not even a bit left in the plug in 6months

It appears to be a common problem with this model Yanmar (4JH4E), maybe because there are no raw water anodes in it.

Perhaps while the heat exchanger is at the engineers an anode could be added, or even some adaptations to the raw water intake plumbing close to the exchanger to accommodate an anode would help.

That's a good idea, I will ask the question.

Probably a silly question, I was thinking of removing the lift muffler to repair nicely now the boat will be out of action for a few weeks minimum.

Will the big stainless exhaust riser be full of water, I am assuming it is.

Select to expand quote

cammd said..
Probably a silly question, I was thinking of removing the lift muffler to repair nicely now the boat will be out of action for a few weeks minimum.

Will the big stainless exhaust riser be full of water, I am assuming it is.

The pipe will not be full of water.
The box should only be 1/4 full look for a drain on the box drain it first.
The exchanger housing is done and the core looks 50/50.
If you are cheap and broke the use JB-weld to build up the lip that hold the o-ring in place and slam it back on.
To save the core so you can use it you need to cut a relief cut in both ends of the housing with a die grinder then use a block of wood and a hammer to push it out.
The 4jh manifold needs to be serviced every 3 to 4 years and it need to have water proof grease applied to the ends on the body where it meets the housing so it will slide out at a later time.
How's the exhaust elbow looks?










The pictures and the cooler are from a 4LH aftercooler butt it's to show where you need to add grease before you put a new one in service,,,,

Side note if your in the water you need to cap any valves that you removed hose's off of and the exhaust hose that feeds from the transom. It's very easy to sink the boat if you don't as it only take a bump on a valve without a cap on it as you are working to open it a bit and have a leak as you fight with the engine and muffler. Nothing worse then to come back and have your boat full of water or sunk....

Great tips cheers, I will be servicing regularly in future when its sorted

I put a cap over the exhaust exit on the transom, got a toothbrush with the head cut off stuffed into the pipe going to the PSS seal, its all I could find at the time (see pic its cable tied to keep it above the water line). On the bottom right of the picture you can see the raw seawater manifold, there is a seacock under the sea strainer and then each outlet on the manifold has a sea cock as well so two seacock's would have to fail.