Lena - Dec 2013.

See here for details of the head/pre-combustion chamber refurb.

| head off 2 | Head off 3 | Exhaust port | 1Gm10 notes |

"Off with her Head - Off with her Head"

The saga of this year is one of many engine problems.

To cut it short - after that long time sitting idle, despite new filters etc and the engine starting ok - power in gear was poor.

Replacing all fuel lines and filters and changing all the fuel, cleaning the tank, checking lift pump etc - still the same. Injector was checked and found to be bolcking some at top pressure. Put in my new spare injector - still the same !

Then running on the mooring - trying to get some revs under load, it suddenly started to rattle and immediately stopped in a blast of white smoke. It seemed horribly terminal at the time !

I took out the injector pump and took it to DTM in Bristol, on the recommendation of Rollo in Gordano.

They tested it and said it was in need of rebuilding.( one can only trust these people )

They put in a new piston and barrel - and new delivery valve ( Yanmar parts )

All then seemed well - and Ian and I set off for Ilfracombe. Halfway down the river the temp warning sounded. After a brief rest it was ok - but went off again out past the Holms. Since it was pumping water and did not feel too over-warm - I took off the wire !

It ran faultlessly to Ilfracombe - despite earlier smoking badly ( black ). I really did not think it was going to make Watchet. But after 8 hrs she was purring away and little smoke !

We tried to dry her out at the Mumbles - but missed the tide a bit, so couldn't reach the intake grating. I put in a new impellor, at much distress in the dark as I had a bolt stuck on the pump body and could not take it out - so had to get the impellor in in situ - not easy !

We carried on over to the Gower - with the temp sender back on, nursing it some - seemed better.

Once home - I checked the temp sender in a water bath and it was spot on on 62 deg.

...it picks up its neg from the block - the single wire is + 12v and that is ON when the temp goes over 62 deg...

I then re-checked the impellor - I had it in backwards ( it was dark and late ! ) so re-did that and went through all the engine mounted piping, fitted a new thermostat, wet exhaust off - everything !

After this trip I set off again to Ilfracombe a week later. It came on again around Porlock ( 15 miles run ) we were motoring into increasing swell - so I took it off again.

This time drying out and cleaning the intake grating which was bad ( barnacles ) Coming back it seemed fine - and was starting ok and seemed to be giving me normal power/revs etc - but still smoking a little at very high revs - which I had never noticed before.

With now being on the new mooring I suppose I'm starting the engine more during very cold winter months - and it seemed it was slower to get going than it had ever been. It also seemed to be still black smoking at full revs under load - but that is not really too unusual.

Wanting to treat the rust on the engine - I decided to strip out the alternator and starter, than check the injector timing.( since I have had the pump rebuilt )

With all the bits stripped - off I'm turning the crank over by hand seeing where the TDC/15 deg marks are - and I'm thinking 'I can't even tell where the compression stoke is' !

Pondering this I poured some oil down the exhaust port with a bit of tube - turning over by hand this stiffened things up - but when I got to TDC I can hear oil fizzy and gurgling out of somewhere ! No sign of anything outside - bit as I go round TDC its definately audibly squidging oil through somewhere.

So - I think this is daft, I have a new head gasket - lets have it off.

More or less as it came off - but I've cleaned out the waterway ports. Pretty good really - better than I expected. Only two ports used on the 1GM10 - the one by the temp sender ( small hole in gasket ) and the one shaped one same side, opposite. All the rest are blanked off by the gasket.

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Quick to do really - just the filter assembly, high pressure lines etc. I had my main tools with me - and I needed to utilise my jack handle tube over a tommy bar to shift the exposed, corroded bolts. The two inner, oil covered bolts were far slacker.

I suspected It may be difficult to actually part the head - but it just lifted off ! I could immediately see oil all over half of it - and the gasket around the tappet hole was all in bits.

The waterway at the small hole in the gasket was completely blocked. This essentially stops water flowing around the head on the side of the temp sender unit. It still could come up from the block at the larger hole and on to the thermostat. This was very possibly the cause of the temp sender reading high.

Now its stripped - the guides are very slightly worn, hardly worth replacing really. I had a 2nd opinion at Jamesons, an old fashioned engineering firm in Bristol - he ultrasonically cleaned the exhaust valve - wow - to convince me the valves were pretty ok !

So have settled on new stem seals - and lap the valves in. Basically this head has never been off - I can see that from the original Yanmar paint job. So the seats are as factory ground. Also - I clocked the head as best I could and its sweet - can't get a 0.05mm feeler under anywhere.

Its also great to clean up and respray all the bits at home ! - and I have great access to the rest of the engine for the same. I still have to check the injector timing - but that will have to wait until I have fuel lines back on to bleed it through.

I shall be very interested to see how the compression feels after its back together. Even when I first started working on this boat some ten years back - I was thinking, 'there's not much compression' - but its always started so sweetly, has never smoked, would give me 5.6kts flat out - so have never felt the need to take things further. Maybe its something that has just recently grown worse. Once something starts leaking, under pressure, its obvious its going to get worse rapidly.

With just new seals - at £12 each, and I have a new gasket - at least its not breaking the bank !

Geoff - Bristol 2013.

PS - I have now definitely sorted out that there 'are' oversized piston and rings available for the 1GM10 - at 0.25 plus. Also rings only at 0.5 plus. Yet the electronic parts catalogue ( which all dealers use ) does not list it as such - even Rollo in Gordano, major dealers in Yanmar, said nothing listed. Apparently on a separate information sheet - part no.

Part no - 105325-22570 piston and rings +.25

105225-22570 - rings +.25

Pro-Ri MArine have them listed | here |

I am considering taking this engine out next year | see here |