Seized engine (Yanmar SB12) - repair or replace ?

[deltaten]

Previous poster recommended checking to see if it truly was frozen.
Good advice.
Fella at marina took on an old boat, sitting open in the yard for 6-7 years. Water inside to the top of the yanmar 2-something. PO said engine was shot/stuck.
Fella pumped out the water, drained the engine changed oil, added fresh fuel and battery. Started up after some fiddling and ran on one cylinder, due to a stuck injector.
He's sailing and enjoying the boat to this day, some 3 years later.

There *could* be a pony under that pile of dung.

[Pegu Club]

The SB 12 is a good old engine, albeit 60/70 year old technology. The SB 12 in our 1977 Bristol when we purchased it was of the sort with no air filter and an oil strainer type device, no oil filter that one would expect to see on an engine. It ran well but was incredibly loud and that old thumper vibrated everything in the boat. We did replace it with a Beta 16. There were bits of rusty metal in the wet exhaust muffler, exactly where those bits of rusty metal originated from I don’t know, but being we were headed out full time cruising we thought a new more reliable engine that was many decibels quieter would be the way to go. We did sell the engine to a chap who was happy to buy it wet exhaust and all. For all I know it is in another boat and is happily and loudly vibrating everything in that boat when running. Good luck with your endeavor.

Fair winds,

[gary howe]

More great replies, all valid I'm sure. This one post has given me lots of confidence with whatever I come across boat wise i.e. knowing all thins knowledge and advice is on hand. Thanks again

[kmacdonald]

Originally Posted by gary howe

More great replies, all valid I'm sure. This one post has given me lots of confidence with whatever I come across boat wise i.e. knowing all thins knowledge and advice is on hand. Thanks again

Just remember, it's worth what you're paying for it.

[WillyTheRat]

Blah, blah blah blah blah blah blah.

Google Yanmar rebuild kit. Found this:
https://www.fridayparts.com/overhaul...SABEgIxgPD_BwE

But I can get you a rebuilt Yanmar for $237,000.00 with only $75,000 down. Beats all of the other prices listed on the forum.

I know nothing about Yanmar engines, but I can use Google.

[GKJ Texoma]

Hello Gary,

Are you the Gary Howe who used to live in Carrollton, Texas??



Graham

[Cheechako]

Buy a used 2GM or similar. Those old SB12's were rough like a thrashing machine . Raw water cooling? Seized? Parts cost? No way.
You cannot make a silk purse out of a sow's ear.

[Joe Mac Phee]

If you have not rebuilt a diesel before, do not be intimidated. This is a single cylinder diesel. It is about as complicated as an anvil. I rebuilt mine! Your biggest problem may be finding a source for parts.

I believe that this is a lightly loaded engine. I did not replace any major components. The bearings, rings and cylinder were well within wear limits.

I think that a frequent failure in this engine is rust-thru of the exhaust elbow. Cooling water can leak back into the cylinder damaging the exhaust valve.

The comment about the "frozen" engine is troubling.
A leaky exhaust valve can show up early as hard start. Engines in boats using raw water cooling can fill the cylinder with water if cranked for long periods of time and not shutting off the cooling water.

Good luck

(This engine is also usually as reliable as an anvil!)

[Wotname]

Originally Posted by WillyTheRat

Blah, blah blah blah blah blah blah.

Google Yanmar rebuild kit. Found this:
https://www.fridayparts.com/overhaul...SABEgIxgPD_BwE

But I can get you a rebuilt Yanmar for $237,000.00 with only $75,000 down. Beats all of the other prices listed on the forum.

I know nothing about Yanmar engines, but I can use Google.

I suggest you hone your google skills as the link you provided has zero parts suitable for the OP's engine with the possible exception of an injector nozzle and perhaps a lift pump.

[kmacdonald]

Punters.

[Wotname]

Gary,

Let me add my voice to those who are suggesting that this engine run might again with minimal effort i.e. no rebuild.

As others have posted...

First thing to do is see if you can get the engine to turn over using the hand start function and decompression lever. If it won't turn, then try rocking it back and forth using the front pulley.

If still no movement, remove the air intake and exhaust pipe and try flooding the chamber by spraying something like WD-40 into the inlet and exhaust port (decompression lever operated). Or if possible, remove the injector and use that hole to introduce the WD-40 (or diesel) into the cylinder head.

Leave for a day or two and try again.

Once you can turn it over, you can see if you have compression. If so, it will likely run without much more work.

If no compression or if you still can't budge it, then it is time to pull the head and see what is what inside.

Don't be put off by the unfounded fears of raw water cooling. These engine were designed for raw water cooling and will last many decades if maintained correctly i.e. keep the anodes up. Descaling occasionally also helps.

However they are noisy and they do vibrate!

[Compass790]

[QUOTE=Wotname;3157019]I suggest you hone your google skills as the link you provided has zero parts suitable for the OP's engine with the possible exception of an injector nozzle and perhaps a lift pump.[/QUOTE

He did say Blah Blah Blah & that described his post perfectly.

Posts 23 to 26 are very useful to the OP if he wants to have a crack at it.

[captlloyd]

[QUOTE=Compass790;3157071]

Originally Posted by Wotname

I suggest you hone your google skills as the link you provided has zero parts suitable for the OP's engine with the possible exception of an injector nozzle and perhaps a lift pump.[/QUOTE

He did say Blah Blah Blah & that described his post perfectly.

Posts 23 to 26 are very useful to the OP if he wants to have a crack at it.

I couldn’t make heads or tails out of anything he is trying to say.

[olaf hart]

Had an SB8, swapped it for a 2gm20.
The noise and vibration were bad, but the gearbox whine in that big old box sent me nuts.
Pulled apart an old YSM8 years before to do a rebuild, everything miked within specs and I just put it back together with new gaskets.
So, for what it is worth, at least see if you can free the engine and /or take a look inside.

[gary howe]

Hi all, thanks again for all the feedback. I've decided to look at a smaller boat that's less of a project and more sailing. If I get to grips with that and enjoy it I can move onto bigger challenges with confidence that it will be worth while.
Regards
Gary