Corrosion On Engine

Allan12210 · Dec 26, 2022

That happened on my 3GMF30. The little drain valve for the seawater side of the heat exchanger was leaking a tiny bit. When I finally discovered it there seemed to be a lot of corrosion present. At first glance it seemed worse than it actually turned out. I removed the entire heat exchanger/exhaust manifold and took it home. The worst part was a bolt holding the mixing elbow to the manifold. It was so rusted I couldn't get a socket on it to unscrew. After removing the other 3 bolts, the entire piece rotated, unscrewing the corroded bolt. Once that was removed I chased all of the threads with a tap, wire brushed everything and repainted with heat resistant paint to match the original color. New gaskets were installed everywhere and the bronze petcock valve was reinstalled with some Teflon tape. One upgrade I did was to replace two of the mixing elbow flange bolts with studs so I could hang the gasket and elbow from them making future removal/installation a lot easier. Nuts and lock washers were used on the studs. While I could see everything easily I also replaced the fuel lift pump as it had 3000+ hours on it after 32 years. It seemed like a good thing to do at the time.

Rich Stidger · Dec 26, 2022

Yup, it looks like a seawater leak. Very common issue with all engines. I don't have your engine but I had a similar corrosion problem with a seeping raw water pump.
Solution: remove the corroded parts if you can. Clean, wire-brush, on or off the engine. Determine the real cause of the leak and fix it. Then buy a small POR-15 kit and the Degreaser and Metal Cleaner-Prep chemicals. You can find it on-line or at auto body supply stores. This is a two-part epoxy coating that will adhere to the engine parts and will stop all corrosion. Follow the application directions explicitly - don't take any shortcuts. After coating the areas with POR-15, paint with matching engine paint.
Problem gone, but watch for repeated leaks at frequent intervals.

jssailem · Dec 26, 2022

Rich Stidger said:
Yup, it looks like a seawater leak. Very common issue with all engines.

Rich Stidger said:
Problem gone, but watch for repeated leaks at frequent intervals.

Sound advice. Regular inspections. Catch the issues early. Makes for a safer happier cruising.

Looking at the images. It appears your corrosion starts near that upper hose and the trail runs down along the gasket. I would start at the top and work my way downwards, cleaning up, sealing, and repairing the damage discovered. It will only get worse.

Ralph Johnstone · Dec 26, 2022

Allan12210 said:
the bronze petcock valve was reinstalled with some Teflon tape.

Using teflon tape ONLY on a threaded joint carrying sea water is sketchy at best. I did this early on when working on the boat before I learned that tape requires paste as well to ensure no leaks. A couple of good ones are :

The only benefit to using teflon tape is that it's clean. Tape and paste are 100% effective in all cases.

Ralph Johnstone · Dec 26, 2022

Had the same thing happen when the vacuum breaker near the engine decided to leak. Hell of a mess but only paint deep. Stripped off everything on the starboard side of the engine and first degreased and then went at it with coarse steel wool.

Yours looks the same as mine and I don't see any corrosion damage so it's a simple case of :

1. Positively ensure all sources of leakage are repaired.
2. Strip off any engine parts that will impeded the cleaning process.
3. Degrease.
4. Use coarse steel to remove the salt deposits and light corrosion.
5. Once down to grey metal, clean and paint with Yanmar block paint.

Definitely not a big deal but does take time and a lot of elbow grease.

Scott T-Bird · Jan 2, 2023

That doesn't look like corrosion to me. All that whitish stuff is mineral deposits from leaking water. The paint is also bubbling and peeling from the water. When properly gasketed, you wouldn't have all these deposits. Sure, there may be some minor corrosion due to all the water leaking. Clean it up and install the gaskets correctly and you won't have these issues.

dlochner · Jan 14, 2023

Removing the heat exchanger should not be too difficult, so long as you have cooperative bolts. The corrosion does look like it has eroded a good deal of metal, which as you surmise, is not good. I suspect this will be more of a pain in the wallet than in the arse.

jssailem · Jan 14, 2023

Opps. That is an issue. Looks like an Aluminum heat exchanger body. You may get lucky and the brass/copper insert may be ok. It would be a slim chance.
Likely a new heat exchanger is in your future. If so it will be a feature should you choose to sell the boat.

heritage · Jan 14, 2023

That can probably be repaired by brazing. The rim can be built up and then honed down to be even with undamaged area.

Ralph Johnstone · Jan 14, 2023

My condolences on that mess. Turned out to be much worse than it looked originally. Hang on to the heat exchanger tube sheets and tubes as they MAY be useable for the next exchanger shell. Each part has to be exactly the same length but I don't know if they are made as a pair. Only your Yanmar dealer knows for sure.

When you do reassemble them, you MUST use a non petroleum grease on the "O" rings to ensure they slide into the right place when you tighten the end caps. That is what caused the leakage with yours. Didn't quite seal.

Ralph Johnstone · Jan 16, 2023

Mclovin said:
I was working on changing water pump on 2001 Yanmar 4JH3-TE 76 hp engine and have some corrosion going on.

I can't speak for your 4JH3-TE, but does it have another cap on the end of the HEX as does my 2GM20F or is it different ? May be able to push and pull ?

The core should slide right out but again this is a smaller engine :

Ralph Johnstone · Jan 17, 2023

Mclovin said:
There is a bunch of corrosion and not sure if is worthe repairing.

I'd really be worried that you may not be able to get a good seal when installing those new big "O" rings. And the cycle repeats itself all over again. The areas of seating surface which remain still do not look too promising :

In fact, it looks downright hopeless. If the ball were in my court, I would definitely be looking for a new housing.

Mclovin said:
if i dont does anyone know where to find the cooler body. i have search and called around with no luck.

Have you called your local Yanmar dealer ? The ultimate in pricey but not much else you can do. Best of luck with this.

dlochner · Jan 18, 2023

The Heat Exchanger looks too corroded to repair. Try Niemiec Marine. I've found them to have the best prices on Yanmar.

https://niemiecmarine.com/

kloudie1 · Jan 18, 2023

In industry, we've rebuilt faces of flanges in low temperature, low pressure service using epoxy composites then machining. As in most adhesive trials, surface preparation must pretty much flawless. We used Belzona composites and had excelllent results that lasted many years. That has the benefit of surface sealing to keep local corrosion at bay.
It may be that grit blast, wire brush, and weld/braze and machine would be the least expensive fix ..

Corrosion On Engine

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