Yanmar YSM12 problems

Earendil-uk

Earendil-uk

Well-Known Member
Joined
27 Jul 2013
Messages
327
Location
zummerzet
Visit site
Sorry if this has been discussed before BUT,
I have just got a new to me Mirage 26 with a Yanmar YSM12 inboard that I knew had a bad oil leak put I thought it was fixable and it was, The main feed oil pipe had burst so I replaced ran the engine for a while no problems. I went out for a bit of a run to get used to the boat and to make sure the engine was OK, not much wind so not pressed hard at all but everything worked fine.
Went out this morning in a fair old blow and was really pleased with the boat lots of hard sailing well heeled over, spent a couple of hours out when we decided to go back into harbour as a fair old storm was brewing. Started the engine and it seemed to choke and would hardly start, opened the engine bay and a cloud of blue smoke poured out ( engine had stopped again), had to sail into harbour and pick up moorings (mmmm interesting experience in a blow ).
Question is ( I did research this engine before buying and knew of its little problems , silly me ) can anything be done to eliminate this problem :- new rings,keep the oil levels a bit low, etc or just get rid of ?
Any advice will be most welcome.
 
Shame you're not based on Discworld, you could get the dwarves to fix it. I suppose you could ask Gandalf, but anyone who knows anything about wizards knows that might not be the best idea. With luck, Viv will be by sometime with words of wisdom.
 
Is the engine now running "normally" on the mooring. As it's now 40+ years old, it's probably well worn. Blue smoke from the engine bay suggests piston blow-by as one possibility. New rings would help, but this problem would show up most of the time. My old YSE exhausted quite a lot of black gungy oil on start up, new rings helped that a lot.
OTH, your comment about keeping oil levels low suggests that you think the sump oil might have run into the cylinder whilst heavily heeled. I suppose that is possible at very high angles, but never happened with me.
Could a bit of sea-water got into the cylinder, again whilst heeled?
Spares are probably still available if you know where to look. Re-engining a Mirage 26 won't be a very cost-effective proposition.
I think Cellar Marine of Helston are good on old Yanmars, ( or were!), maybe worth contacting them for advice.
 
The first check is the exhaust elbow which can get blocked. Worn piston rings result in pressure in the crankcase which causes oil to come out through the breather or the dipstick hole. If the top of the engine is always oily, it is probably worn rings.

It is fairly easy to get the valves reground, and to replace the piston rings and the cylinder liner. I did all this on mine and it now runs well. But it cost around £600 in parts.

The workshop manual is good and is available online.

These engines have a tendency to run away on their lubricating oil, when worn, so keeping the level lowish is a good idea until it is fixed. Also pre-plan how to stop it (something hard across the air intake like a chopping board or a block of wood) because if it does run away it is really scary.

I posted various questions about this problem about five years ago. I can send links I think. I never had the smoke inside the boat that you experienced, but had lots of blue smoke from exhaust after about 20 minutes running.

Good luck. Happy to share experience it is helpful.

Dave
 
Last edited:
Thank you for your replies, I do have a plan in place for the "runaway syndrome" a jam jar lid just right for the air intake kept just inside the engine bay, but this was a bit different when I went to start the engine it was very sluggish like I had picked up a rope so I used the crank handle and de-compressor to make sure it was running freely, it was, maybe battery so started with handle and away she went then smoke appeared everywhere from the engine bay.
 
Mainly port or stbd tacks? With the flat cylinder to stbd, port tack could swill lube oil towards it if overfilled.

Typing on Rivendell in Plymouth, good for my Elf....
 
Last edited:
NickRobinson said:
Mainly port or stbd tacks? With the flat cylinder to stbd, port tack could swill lube oil towards it.

Typing on Rivendell in Plymouth, good for my Elf....
Click to expand...

Thanks for your reply Nick , very difficult to know the guilty tack as we were just "racing around the buoys" :rolleyes: so multiple types of tacks but going by some of the angles of heels I am sure it could have filled the cylinder up with oil. One wonders if engine designers actually know how their engines are being used or even care with the many flaws in design especially on marine engines.
 
Earendil-uk said:
Thanks for your reply Nick , very difficult to know the guilty tack as we were just "racing around the buoys" :rolleyes: so multiple types of tacks but going by some of the angles of heels I am sure it could have filled the cylinder up with oil. One wonders if engine designers actually know how their engines are being used or even care with the many flaws in design especially on marine engines.
Click to expand...

The YSM engines may have been designed to be fitted low into landing craft, so heel not likely-

The YSM in my slow old Macwester did not have to worry about excessive heel. I have the Yanmar QM 18th twin in my Mirage 2700. So much quieter! http://britainbyrivendell.weebly.com/

N
 
Daft question, but when was the engine last serviced?

My original YSB8G is still working as well as the day she was put in the boat.
 
Camelia said:
Daft question, but when was the engine last serviced?

My original YSB8G is still working as well as the day she was put in the boat.
Click to expand...

This I don't know, but the oil was cleanish,starts on the button (well in harbour before going out) sounded very sweet when running , does vibrate a bit but put that down to being a single and I have not run her on high revs as yet. I am at a quandary at the moment as to whether to service it or take the engine out and give it a good going over .
Nice to see some Mirage owners responding :encouragement:
 
You must log in or register to reply here.

Other threads that may be of interest

O
“The Dog that Didn’t Bark:” Yanmar. 4L HASTE.
Replies
2
Views
265
oldgit
O
F
ID this engine part please - 3GM30
Replies
6
Views
206
fredrussell
F

Share this page

Top