Yanmar Leaking

[Key Wester]

A better solution would be to install an actual Yanmar plug, as they are made of stainless steel. Joe

[LittleWing77]

Right on, John!

Thanks for the update.

Wottie (the King ) - what is the purpose of those freezing plugs? To keep the block from cracking?

LittleWing77

Originally Posted by johnmc618

...I then waited 24 hours as recommended by the gasket maker substance. Started the engine up and no more leak!

Video of engine Yanmar 1GM10 running without leak:

https://streamable.com/1u8jid

[cal40john]

Originally Posted by LittleWing77

Right on, John!

Thanks for the update.

Wottie (the King ) - what is the purpose of those freezing plugs? To keep the block from cracking?

LittleWing77

Engine blocks are made by pouring liquid metal into a sand casting. The sand in the internal water galleys have to reach the inside of the mold. The sand forming the internal galleys otherwise have to float in the air without support before the metal is added. The core plugs are where the sand supports are located.

https://en.wikipedia.org/wiki/Core_p...tion%20engines.

[Compass790]

Originally Posted by Key Wester

A better solution would be to install an actual Yanmar plug, as they are made of stainless steel. Joe

What he said +1
I believe your engine is raw water cooled & a non-ss freeze plug wont last very long if using boat in salt water. How long I cant say as having an anode will help.

[Rob_P]

Originally Posted by Compass790

What he said +1
I believe your engine is raw water cooled & a non-ss freeze plug wont last very long if using boat in salt water. How long I cant say as having an anode will help.

All core plugs rot, even in engines that use coolant. It's the nature of the beast and why they're so plentiful everywhere as generic replacements.


For me, I'd have used brass. I would also have painted the water-side of the plug with enamel and then baked it in the oven on really low temp instead of using bare steel to set the enamel as a solid protective surface. Bare steel will rot out fairly fast in a raw water environment, brass lasts longer and enameled brass lasts the longest, but at least you know how to fix it when it does fail again.

When installing, the use of gasket material on the block, not the plug, will help seal it and the gasket sealer forms a little bead around the internal edge when the plug is pushed into place. When using a water-side painted plug, that bead protects the plug in the area the paint stops or gets chipped/scraped off during installation.

Hopefully, the rust that's visible in the before picture was totally cleaned off before installing the new core plug. If not, it will hasten the rot of the new plug. Again, at least you know how to fix it when it does rot out.

[johnmc618]

All good advice, and if I need to replace again, will definitely utilize. I’m currently in freshwater so hopefully will mitigate some of the corrosion.

Thanks guys (and gals)!