What does rebuild actually mean?

[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?

[Rumrace]

You can’t do a block rebuild in the boat. Once the bores are straight it just tossing in parts but big end bearing are a lot easier on an engine stand. Price out a rebuilt or new motor. Price is silly cheap. If the engine needs a REnRE then when was the transmission done? If you pull the head and find a 10 thou lip on the barrels I’d replace it for a trade in.

[Pete7]

Is a workshop manual available for that engine so you can measure things like pistons and crank journals?

However, before you start, is the compression within spec? If so, what are you hoping to achieve tearing an engine apart?


Pete

[Ballsnall]

Originally Posted by rockin411

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?

Rebuild is very subjective, it could mean just new rings and bearings because thats all that was required.
There's top end rebuild, bottom end rebuild and full rebuild which may or may not include injectors & pump.

So just replace what is worn out which will require a strip down, clean and measure to determine condition.
Most people would replace rings and bearings regardless as they are cheap and easy to do with the engine stripped. A head job is also advisable if your engine has significant hrs

[Tellie]

I'd at least attempt a re-build. As mentioned before, these are fairly cheap to buy new as marine engines go. Nothing more satisfying and rewarding, than fixing your own boat systems. It's not a 12 cylinder, a single lunger is fairly straight forward and comparatively light. You re-build this yourself and you'll be far more qualified on your engine than most are on theirs. If you're looking for far flung sailing adventures knowing your engine intimately will pay off in huge benefits
in the long run.

[Fore and Aft]

Rockin411 if you're selling the boat then a quick wipe with a clean rag and some new engine paint is all that is needed. Then a bottle of Oil Smoke Stop should take care of the other issues. I am told the hardest part of this rebuild is keeping a straight face when potential buyers are onboard.
I have surveyed a few boats with Dulux rebuilds.
Cheers

https://www.liqui-moly.com/en/oil-sm...0012.html#2122

[nhschneider]

As has been said, there is no clear definition of the word ‘rebuild’. Some might assume it means that wear items have been replaced but some people can be fast and loose with the term, either because they’re deceitful or ignorant. Even the term ‘overhaul’ lacks clear specifics.

In my opinion, if someone told me that an engine had been rebuilt or overhauled, I’d ask to see a list of parts that were installed and I would assume nothing. Rebuilding or overhauling an engine can be very rewarding but I have also seen mistakes made that wound up costing someone far more than if they had just bought a new engine outright. If the experience is something to which you’d look forward to, I’d say, “Go for it!” But if you just want to get underway quickly, I’d suggest you look into a long block that was remanufactured by a reputable source.

Good luck, fair winds and calm seas.

[Cwens]

There's a well-defined standard procedure:

1. Completely disassemble the engine
2. Any particularly dirty parts, swish around in solvent
3. Reassemble the engine.
4. At this point, there will be extra parts left over. Save them as spares.

[ABJ87]

Let’s not leave out the “Aerosol Overhaul” or “Rattle Can Rebuild” a hastily applied coat of paint. Commonly done before selling on the internet.

[dlj]

Makes me think of a joke.

There was this old man who had made an enormous fortune. He was tired of running his economic empire and decided he needed to hire an accountant. Now the trouble was, he actually did not know how to read or write so he was thinking about how to go through the interview process. So he had an ad posted looking for an accountant and the selected day for interviews had arrived. There were three candidates in his waiting room. So he called in the first candidate and explained that he didn't know how to read or write so he couldn't read the persons resume. He said the best he could do would be to ask a question. So he asks: "What's 2 + 2? The candidate responds, 4. He thanks the candidate, dismisses that candidate and brings in the second candidate, with again the same explanation and question, eliciting the same response, 4. He thanks the candidate very much and brings in the third candidate with the same explanation and question. But this candidate, sat for a second thinking, then got up, looked out the windows, closed the curtains, made sure no one was listening at the door, came back close and quietly asked the old man, "How much do you want it to be?"

dj

[Wotname]

Listen to Pete!

Originally Posted by Pete7

Is a workshop manual available for that engine so you can measure things like pistons and crank journals?

However, before you start, is the compression within spec? If so, what are you hoping to achieve tearing an engine apart?


Pete

Yes, there is a manual and it gives all the data necessary to check all the wear specs. Only once the engine is apart and you measure stuff, can you decide how far you want to go and what is needed. You can measure everything on this engine with a set of feeler gauges and a vernier calliper (or digital callipers).

At a minimum - rings, a big end bearing and valves.
Next - new piston, new sleeve and main bearings.

While removing the sleeve and main bearing can be done without a press, it is much easier if you have access to a press.

Refitting the sleeve is easy enough by hand but fitting the main bearings is easier with a press although it can be done without.

It the piston and sleeve measure less than half worn, leave then alone as they have already lasted 40 years and will probably outlast you. Likewise the main bearings, if they are less than half worn, it isn't worth the effort to remove and refit them.

[Lepke]

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

[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?

[dlj]

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?

Do you have all the manuals etc?

As far as I know, you have to use a Yanmar distributor.

Is the SB12 the vertically oriented single cylinder model? I used to have the YSB12 which is the horizontally oriented cylinder.

dj

p.s. If you think the compression is bad, why don't you do a compression test?

[rockin411]

Originally Posted by dlj

Do you have all the manuals etc?

As far as I know, you have to use a Yanmar distributor.

Is the SB12 the vertically oriented single cylinder model? I used to have the YSB12 which is the horizontally oriented cylinder.

dj

p.s. If you think the compression is bad, why don't you do a compression test?

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.