What does rebuild actually mean?

[dlj]

I've not done compression testing on these engines. So if there is some kind of special method, I'm not aware. I am attaching another document that you may find useful (hope so anyway).

dj

[dlj]

Here's another document, it's specifically for the YSB, but there might be something useful there for you...

dj

[Madehn]

if i had it apart to do a rebuild, i would put in new rings, new rod bearings, new main bearings, hone out the cyclinder(s), removing any lip- take the head and valves to a shop and have the valves reseated and valve guides replaced if the engine has them. - if any valves were burnt or not sealing, replace them. Look at the engine cam and ensure that there is no excessive wear on the surfaces (unlikely but now is the time to check) If it is a single cyclinder engine then pull the engine and tranny out of the boat- you will be thanking your deity you did it that way later and it is not that hard. While you have it out, replace or rebuild any water pumps both raw and fresh water that the engine may have- my preference there would be to replace them and save the old ones as spared. put a set of new motor mounts on the list while you are at it.
When you are done you will find it was a rewarding experience and you now are very conversant with your engine- when reassembling it, remember that cleanliness is indeed next to godliness. KEEP EVERYTHING SPOTLESS.one last thing- before firing it up be SURE that you replaced the oil in the crankcase and the transmission fluids. it sounds daunting but is not that bad really- as a 17 year old kid i tore into the 383 chrysler engine in my car and rebuilt it doing everything above plus a new oil pump, distributor, etc with no real knowledge when i started. It took awhile but i got it done and drove the car another 100K miles before it started to smoke again. great winter project and you will find it easier than you think.

[NPCampbell]

In general, a rebuild should inspect every internal engine part that moves against or through another part. If a journal, shaft or cylinder is out of spec it needs to either be replaced, machined, sleeved, etc. So pistons, rods, valves, crank, cams, rockers, lifters, etc

Internal bearings, seals, gaskets, o-rings, belts, springs and chains are typically replaced regardless of condition.

[Ballsnall]

Originally Posted by rockin411

I'll go ahead and get rings and bearings knowing that at a minimum I'll need to replace those. My fear is that I get it apart and then it takes weeks to get parts.

Don't forget to pre-order the full gasket kit as well.

[Wotname]

Originally Posted by dlj

Here's another document, it's not specifically for the YSB, but there might be something useful there for you...

dj

Fixed it for you

[dlj]

Originally Posted by Wotname

Fixed it for you

Thank you - definitely dropped a the NOT...

dj

[mvweebles]

Originally Posted by Lepke

You can do a minor overhaul, but rebuild means bringing clearances, etc., in the whole motor, back to like new.

The entire thread dances around what amounts to different flavors of minor rebuilt. This is the right answer for what an unqualified rebuild means.

[Wotname]

Originally Posted by rockin411

Yes, I have a few manuals with specs. I think I have the YSE, YSB and SB manuals and from all of those I'm able to work on it. None of them are great on their own, but used in conjunction with the parts manual you can figure most everything out.

The SB is the vertical cylinder model and YSB has the horizontal.

The only thing I've seen for doing a compression test involved using an old piston and attaching a gauge to that - i don't have an old piston? Any other options for a compression test with this engine?

I should also add that I'm in an inland lake so there are no options for marine diesel technicians/support.

Get hold of the YSM manual as well. For the work you are planning, the YSM is identical to the YSE, YSB, & SB but it gives much greater detail and explanation than the earlier manuals. Any differences between the models are obvious.



Is there any engine or head rebuilding shop in your area? If so, take the head to them along with the two valves and have them recut the seats and fit the valves. AFAIK, there are no valve guides (or valve seals) in the SB head but they can confirm that and measure the wear anyhow.

AFAIK, the only difference between YSE and YSB is the gearbox housing material; the YSE is cast iron and the YSB is cast alloy and AFIK, the SB gearbox is also alloy.

[Wotname]

Originally Posted by rockin411

Thanks Wotname and everyone for the replies!

I should have prefaced it with the fact that before it stopped wanting to start it was smoking, leaking and burning oil - but actually ran great other than that. All of my research and discussions with others is that the compression is bad - i've exhausted every possibility with fuel problems.

I'll go ahead and get rings and bearings knowing that at a minimum I'll need to replace those. My fear is that I get it apart and then it takes weeks to get parts.

Anyone have a suggestion on a good source for 1977 Yanmar SB12 parts?

Yep get the rings but check the price of the piston, it may be worth getting a new one anyhow.
Get the two valves as well, the old ones are well used by now .
Get a head gasket (or even two).
The rest of the gaskets can be made without too much effort but maybe you might prefer to get an exhaust pipe gasket rather than making your own.

[c.K.]

Originally Posted by rockin411

I've posted a few recent threads about my 1 cylinder Yanmar SB12 and am thinking of going down that path. If I do I'm hoping to raise it up in the boat and rebuild there. What do people mean when they say rebuild? Is it just new rings, new cylinder sleeve, valves and that's it? What else should be done?

Hey 411
Had some non start issues with my 4 cylinder Perkins 1989 low time engine a mechanic had a look at it and suggested a new engine
well I never had any problems so I decided to hoist this 420 lbs bock out and take it to a dealer that has a machine shop
They got it running did some compression tests (good) and advised to overhaul the injectors, fuel pump, adjust and check the head, new oil pan gasket and starter ring around my fly wheel and new waterpump that they broke
Total cost $8600 can runs like new and I'm very happy I did not go for a new block that would have cost me around $30.000 can: this price also due to the fact that you have to hire a certified mechanic to do the work in order to keep the warranty
good luck with your project
Runs like

[MJH]

Originally Posted by rockin411

I've posted a few recent threads about my 1 cylinder Yanmar SB12 and am thinking of going down that path. If I do I'm hoping to raise it up in the boat and rebuild there. What do people mean when they say rebuild? Is it just new rings, new cylinder sleeve, valves and that's it? What else should be done?

As you can tell from all the replies, a rebuild can mean anything. Bottom line, a rebuild is only as good as the man that did the job. In the end the engine's age hasn't changed.

[Ballsnall]

Originally Posted by MJH

Bottom line, a rebuild is only as good as the man that did the job.

Or woman, but its not too difficult or technical if you take your time and have a good manual.

In the end the engine's age hasn't changed.

I would tend to disagree, engine age is measured in run hours or more accurately fuel burn so a "fully" rebuild engine is equivalent to a new one with the same life expectancy of the original.

[MJH]

Originally Posted by Ballsnall

Or woman, but its not too difficult or technical if you take your time and have a good manual.

I would tend to disagree, engine age is measured in run hours or more accurately fuel burn so a "fully" rebuild engine is equivalent to a new one with the same life expectancy of the original.

Given two boats exactly the same except for the engine, one engine make and model that sold 10-20 years prior and has been rebuilt and the other with a new engine, I know which one I would pick. There is more to the engine rebuild/replacement decision than life expectancy, even giving a rebuild the benefit of the doubt.

[dlj]

Originally Posted by Ballsnall

Or woman, but its not too difficult or technical if you take your time and have a good manual.

I would tend to disagree, engine age is measured in run hours or more accurately fuel burn so a "fully" rebuild engine is equivalent to a new one with the same life expectancy of the original.

I'd even go so far as to say a properly rebuilt engine may actually be better than a stock new one. But you need a good machinist for that...

dj