Yanmar Y5M12

[Ralph]

I have recently bought a Gib'Sea 28 with a Yanmar Y5M12 engine. I have to service the engine and may possibly have a water leak on the head gasket. There are signs of a leak but as she is on the hard it's very difficult to tell so I'll have to take the head off to be sure. As I have never worked on a marine diesel before I would like to get an equivilent of a 'Haynes Manual' for the engine. Does such a thing exist? I am a time served engineer and have worked on car and bike petrol engines so I can see no reason why I shouldn't be able to learn but diving in blind I feel is not to be advised especially when working in such confined spaces.

 

[Chris_Stannard]

Your local Yanmar agent should be able to sell you a workshop manual, which is not quite as explicit as Haynes, but fine if you know the basics anyway

Goodluck

 

[jfkal]

Agree. If you have some experience with engines the official service manual (get the parts manual as well) will definately do. Was my best investment. Now the yards are not making money from me anymore on this one ))

 

[vyv_cox]

There is, in fact, a Haynes manual for general marine engines. Look at http://www.haynes.co.uk/inc/viewbook.asp?bt=H975 for some details.

 

[johnt]

theres nothing tricky in taking the head of a YSM 12 ..and the tappet clearance is 8 thou ..email me if you want more info

 

[waterrat365]

I recently rebult a YSM8, a single cylinder. There are 4 big nuts to remove. First, pull the injector and take it to a mechanic for testing. Remove the lube oil feed lines, carefully saving and noting the order of all washers. The injector, BTW, has several insulating washers and a copper compression washer which must be replaced as new (the manual helps here a lot, with great cut-away schematics. Remove the head nuts, pull the head, and bring it to a machione shop for grinding. This must be done. If the head gasket blew, then there is probably a warp, which will prevent a new gasket from sealing. Replace and seat the valves while you're at it. When the head is in the shop, keep the open cylinder covered with oil to prevent rust. Scrape all traces of the old gasketing and look for burns in the block. If you don't see any channeling (probably won't), when you get the re-built head, put sealant on the new gasket, place it carefully on the block, put the head on the gasket, and bolt it up with a torque wrench to specs. Cleanliness counts here. Then replace all washers on the fuel lines (use new ones-they're cheap and the old ones get hardened from usage) and then, while your at it, replace all the fuel lines, as these are probably shot by now and you'll kick yourself if they let go the first time you start the engine, which they might. They did for me. Replace the tested or re-built/new injector with new washers, tighten the fuel line and bleed it. Replace all lube oil lines. Should start. Look for leaks. BTW, don't fiddle with the injector pump or governor at all ever. And don't forget to re-torque the head at 50 hours. Failure to do so will shorten your engine life. Happy sailing, Cliff Moore, SV PELORUS, USA

 

[oldsaltoz]

Re: Yanmar test

G’day again Ralph.
Have you tried stuffing a garden hose up the engine water intake and run the engine to see if you have a problem that requires the removal of the head?

Avagoodweekend Old Salt Oz……

 

[Ralph]

Re: Yanmar test

Sadly the yard in which my boat is in at present might charge like a wounded rhino but are short on facilities like hoses and electricity. I don't think that it would be a bad idea to have the head off anyway and get the injector cleaned at the same time and check the tappets etc. At least then I'll have more of an idea of the state of the engine and having been intimate with it, if it's going to cause me grief at sea at least I'll have some idea what does what.

 

[vyv_cox]

Hello, Cliif. Haven't seen you around for a while.

I did a single cylinder Yanmar a few years ago, it had blown a gasket due to loosening of the head bolts. This was the 12 HP version, a vertical although most were horizontal. These bolts have a very coarse thread and I guess the previous maintainer had not got them tight enough. I did the job on the water but took the head home. Managed to get the head flat enough with a pane of glass and grinding compound but there was a small channel in the cylinder. I did a quality botch job on that, put a small piece of aluminium foil and lots of gasket goo in the channel to last the few weeks until the end of the season. It worked so well that I never got around to changing it and sold the boat a year later.

One other little tip on this engine. There is a very small coolant drilling in the head, about 5 mm diameter, that gets blocked by a mixture of carbon and salt. If you don't know it's there you can easily miss it. If it blocks it causes the engine to fail although it usually re-starts after a few minutes. Very confusing and sometimes somewhat dangerous. A drill will clean it out.

Vyv