Freeze plug on Yanmar 6lpa-stp

[Albesaurus]

Hello everyone,

I had my 2002 6LPA-STP removed and brought to Roger (Sherman Marine) this past November. Besides replacing a rotted oil pan, timing belt and service all the coolers. He will also be investigating the known freeze plug that rot out just behind the raw water pump.

As many of you know a blown seal on the raw water pump spays salt water in the tight area and a few of you had that plug rot out and fail while underway…. Since the engine is out i want him to address it so I don’t have this potential catastrophic outcome.

The question is how was this plug ( or whatever it is) replaced. I read all the posts ( and so has Roger) but we couldn’t find info on how it was replaced or what was done?

Thanks for any info.

[Tree]

Mine I pulled out and tapped a 3/4 unf hole - fitted a bolt with a seal behind it. Never going to be a problem ever again.

However - it is the only core plug on the engine that isn’t stainless steel as it is fitted by Toyota on the block assembly line. FYI it is 16mm in diameter and stainless steel options are very available. You will need to pull the fuel pump to remove it and fit successfully.

[Albesaurus]

Thanks Tree. Did you do it in the boat?

[Tree]

Afraid not. Was an engine out job due to removing the fuel pump. Some boats have enough room to pull the fuel pump but mine is too tight against the bulkhead.

[WillieC]

Is the engine already back in the boat? If so it all depends on accessibility.

I only mention this because I replaced all the plugs in my Volvo Penta MD17C when I had it apart on the bench. Most are Welch plugs, used in the casting process. Many of them are completely inaccessible when the engine is put back together, specifically on the individual cylinder heads.

Not having done this operation in my varied careers, though I recall my dad showing me what a freeze plug was and what it did, I was unsure how much force would be required to obtain a good seal. The VP uses slight domed flat-ish plugs, not the more common cup style. The first time i had the engine apart I meticulously cleaned rust and scale from the plug seats and used my $125 harbor freight press. (The Hammer and Socket method I read about left too many questions for me.) Apparently, I didn't quite give it enough oomph and a couple weeped and so did I. Fortunately, I got the opportunity to tear it all apart after I had reinstalled it in the boat. Long Storie(s).

I hope you get this sorted. Leaving a plain steel plug sounds like trouble brewing. Surprised to see it was apparently overlooked.

[WillieC]

Yikes! Engine out to replace fuel pump?? Note to self...keep the A25.

[Tree]

There is one thing you can do and something I didn’t. You could fill the entire plug with an epoxy metal product. It would never fail that way. I had plans to pull the engine as it had too much rust on it for my liking but that plan came early with the plug failure. I always joke that the one freeze plug cost me around £3500 to repair. That did include needle gunning the engine all over and repainting with two part epoxy primer and two part yanmar coloured paint. 8 years later and you could still eat your dinner from that engine it looks so clean. I do have plans to pull the engine possibly this year just to go round it and check everything - also I would like to get the fuel pump overhauled as it now has 2300 hours on it and no record of being pulled and re calibrated in the previous years since I bought the boat.

[Albesaurus]

Yes. Engine is still out of the boat. Now i have other issues…. See my post from today on my skeg repair…. In 28TE section

[Albesaurus]

Update… mechanic says the old plug was pretty thin. So a good suggestion to change it before the eventual failure.

Looking forward to getting her all repainted and back in the boat!

[WillieC]

Excellent!

[roaringcreek86]

anyone know a mechanic in south nj that can replace or thread and bolt a freeze plug in a yanmar 6lpa-stp? tried to replace guess engine has to come out

[roaringcreek86]

tapped with motor in boat

[roaringcreek86]

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