Yanmar 1GM10 woes

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DownWest

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Hi
Helping a friend with his boat. The engine has been sitting for several years (8) before he bought it and was 'winterised' when parked. Turned OK, but 'bumped' at TDC and would not do a complete rev.
Rocker cover off and exhaust valve was stuck. So, head off and found that it was not only stuck, but was corroded along with the seat. Machinist fitted a new seat and we sourced a new valve from UK.
So, back on the boat and cleaning up the block to refit with the head. Now, it lives under the bridgedeck and access is difficult. So one can only see the the back of the bore. Cleaning up the scrapings, it became apparent that there was pitting on the forward edge of the bore. Quite extensive, but not below the line of the top ring.
So the question is: With the budget having several hits on the engine and a few other problems. Will this engine run OK for this season? Obviously it needs pulling and re-sleeving, but the time and cost is tricky for this year.
While having quite a lot of experience on donks, this is a new one. If the pitting is above the top ring, how might that effect things?
Any comments welcome!
DW
 
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DownWest said:
Turned OK, but 'bumped' at TDC and would not do a complete rev.
Click to expand...

These engines are notorious for bending their rather weedy connecting rods if they get water in the cylinder. A stuck valve may well have done the same. There is a checking method in the manual - involves crushing solder poked down the injector hole.

Rocker cover off and exhaust valve was stuck. So, head off and found that it was not only stuck, but was corroded along with the seat. ... Cleaning up the scrapings, it became apparent that there was pitting on the forward edge of the bore. Quite extensive, but not below the line of the top ring.
Click to expand...

Sounds stuffed to me. Sorry.
 
With the head off - check the new gasket thickness. Top clearance is between 0.68 mm - 0.88 mm ( Yanmar manual specs )
Since the flat head sits on the gasket - then the piston at tdc should be above the top of the block by the difference between top clearance and gasket thickness.
ie - if the gasket is 2mm thick - then the piston at tdc should be about 1.3 mm max ABOVE the block face without the gasket.

These blocks are thin - and Yanmar only recommend I rebore at 0.25 mm oversized. There is no liner. Its a cast block. Oversized piston and rings are hard to source but are made ( or were 4 years ago ! ) and only + 0.25mm.

If the bore feels ok when at bottom - I would say stick it back together as is - but do check the exhaust elbow inner liner for corrosion ( holes )

Also - make sure while the head is off the exhaust port is clean of carbon ( they bung up badly - and can get corrosion damage into the side of the tappet galleries.
 
Nemo and Jumble
My reaction was that it would be an idea to pull it it at the end of the season and bore out the block and insert a sleeve to get it back to std size, so as to re-use the piston etc. Possibly with new rings. Done that with other engines before, but it does sound a bit iffy if the block is thin. .25 oversize is not going to be enough to remove the pitting. Even if we can find the piston..
Don't think the rod is bent, it was turned by hand when then the 'bump' was discovered. Checked the elbow and it looked OK, if a bit rusty. And the head was pressure checked when the valve seat was fitted, so the known prob with the tappet galleries is OK, even if the port was a bit rough.
Looks like we will suck it and see. All bolted up now....
 
Maybe it can be re-lined - the meat is probably there ? -
Certainly 4 years back an oversized piston and rings was available at 0.25. Even then - most dealers told me it did not exist - as it was not on the Yanmar parts database ! It was listed on a paper database !

Part no - 105325-22570 piston and rings +.25 - 1GM10
105225-22570 - rings +.25 only.
There were also .50 rings listed but manual says not to bore over .25, which seemed odd ? I don't have the number for them

.As said - it was a muddy area - I was considering a rebuild at the time !
Maybe the .50 rings are still available. Do not believe the parts fisch - try to contact Yanmar direct with those part no's if you go down that road.

Apart from these issues - they are fairly simple to stripdown. No special tools really - just an awkward large main nut on the end of the governor shaft.

I think the problem is this is basically an old block casting - original to the early engines - hence the water ports not matching the new head gasket. I think it has been already bored out to take a larger piston ?
 
Nemo
Thanks for helping.
Both the head and block have 6(?) matching water holes in their faces, but several are blanked by the gasket. I will try and find out from a dealer if it is possible to sleeve these engines, don't think it has been bored as nothing stamped on the piston. Friend is sweating a bit, as the idea of a new engine will really foul up the budget, esp as it will not be one of these and will require all sorts of extra bits. Apart from the time it would take.
DW
 
Won't help the budget concerns, but a Nanni 10 or 14 is virtually a direct replacement for the 1GM. I did it very easily in my boat and can give you a list of the changes needed if he wishes to go down that route. If the boat is a keeper then well worth doing as the Nanni is a real improvement.
 
nemodreams said:
I think the problem is this is basically an old block casting - original to the early engines - hence the water ports not matching the new head gasket. I think it has been already bored out to take a larger piston ?
Click to expand...

1GM10 head gaskets are weird - they have all sort of holes in them which don't match up with anything. It's also not at all clear which way up they go; the manual says that one side is marked "top" but the genuine Yanmar one I used had no markings at all and could physically go either way up. From memory you have to match the copper inset ring with the live oilway ...
 
JumbleDuck said:
1GM10 head gaskets are weird - they have all sort of holes in them which don't match up with anything. It's also not at all clear which way up they go; the manual says that one side is marked "top" but the genuine Yanmar one I used had no markings at all and could physically go either way up. From memory you have to match the copper inset ring with the live oilway ...
Click to expand...

Live oilway? This has an exterior oïl feed for the rockers via a banjo behind the airfilter. The gasket was identical with the used one and had a number and 'TOP' in the same place.
About wear, there is no 'step' at the top of the bore. Quite smooth. (until you feel the pitting...)

Tranona
Thanks for the Nanni info. If sleeving will sort this one, then it will do for a while. The idea of shelling out several thou on a new engine and installation is spoiling his summer. The boat is a Trapper 501 and I really like it. Seems well built and in pretty good nik. All the problems stem from being parked for 8+ yrs. We will find out tomorrow if it runs OK.
Bit of a time capsule, Seafarer depth and log units , old Autohelm with the compass dial on top. Changed the former for new kit, will see if the later still keeps a course...
 
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JumbleDuck said:
1GM10 head gaskets are weird - they have all sort of holes in them which don't match up with anything. It's also not at all clear which way up they go; the manual says that one side is marked "top" but the genuine Yanmar one I used had no markings at all and could physically go either way up. From memory you have to match the copper inset ring with the live oilway ...
Click to expand...

Yanmar say 'top' - but my original was marked with an 'A'.( eng circa 1993 ) My new gasket had an 'A' on it ( genuine ) Also their workshop manual diagram is printed backwards - which does not help.
see this page on my website
http://www.lena.geoffrichings.co.uk/sail_site/headoff-wrong-info.html
( their Gear Side means timing gears - ie opposite to flywheel side )

That gasket shown is the original yanmar gasket from an original undisturbed head - viewed there from the starter motor side. The metal faces up - and the two holes are the opposite side to the thermo housing. NO gasket sealant ( another myth still printed in their manual ! )

ditto - I don't know what you mean by live oilway - there are only waterways. All oil feed is external piping.
 
DownWest said:
Live oilway?
Click to expand...

Oops.

nemodreams said:
Yanmar say 'top' - but my original was marked with an 'A'.( eng circa 1993 ) My new gasket had an 'A' on it ( genuine ) Also their workshop manual diagram is printed backwards - which does not help.
see this page on my website
http://www.lena.geoffrichings.co.uk/sail_site/headoff-wrong-info.html
Click to expand...

That's very interesting because from memory - it's three years since I changed the head - my gasket was almost entirely symmetrical, unlike yours. It had unnecessary holes all over the place. It came in Yanmar packaging from a US Yanmar dealer, so I am pretty sure it was genuine.

ditto - I don't know what you mean by live oilway - there are only waterways. All oil feed is external piping.
Click to expand...

Oops again. Waterway.
 
Provided compression is good it should be OK, don't forget to check the exhaiust / mixer pipe for corrosion as if corroded this allows sea water to then corrade the exhaust port and possibly enter the engine (may be cause of your pitting). When starting if it it turns over lots but doesn't fire make sure you pull the stop cable as they can fire and run backwards with bad consequences... Air in the fuel system is the main case of poor startign so don't be afraid to bleed the thing really thouroghly
 
Niander said:
Pitting above top ring won't affect it at all have you tried starting it yet?
Click to expand...

Off to the boat in a few minutes to try her.

Dave, We are fitting a bulb pump in the line for bleeding and thanks for the tip about running backwards.

Will get back later. X-fingers :o
DW
 
Well. Fitted the outboard style bulb primer into the fuel line. Made bleeding a doddle, all done in a minute or two. Turned with the decompressor, couple of revs to ensure free and then started her. Fired up quickly and then noticed a squirt of oïl from low down. Couple of bruised knuckles later, had the lower oïl pipe off, which had a corrosion pit right through the banjo. BUT, not unhappy, as it looks to be good for a while. Pipe on the bench for a bit of silver soldering to plug the hole. (Had to replace the upper pipe with copper earlier, as it had disintergrated..)
Thanks for the comments and help. Friend very relieved......
DW
 
DownWest said:
Well. Fitted the outboard style bulb primer into the fuel line. Made bleeding a doddle, all done in a minute or two. Turned with the decompressor, couple of revs to ensure free and then started her. Fired up quickly and then noticed a squirt of oïl from low down. Couple of bruised knuckles later, had the lower oïl pipe off, which had a corrosion pit right through the banjo. BUT, not unhappy, as it looks to be good for a while. Pipe on the bench for a bit of silver soldering to plug the hole. (Had to replace the upper pipe with copper earlier, as it had disintergrated..)
Thanks for the comments and help. Friend very relieved......
DW
Click to expand...

Good news. I replaced both my oil pipes with rubber ones from Pirtek, which they made up in ten minutes and cost me £35-ish the pair.
 
I used a power steering rubber hose, banjo each end, from the local scrappy, I forget now which vehicle but I looked under all the bonnets til I found something suitable - cost was £1
 
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