Maybe buying used Yanmar 3GM30F

[rpeebles]

What are parts availability and what weak points should I check before installation? I am replacing a Volvo MD3B or MD17C not sure which. Thanks, Roger

[roverhi]

You are going to have less hp/torque with the 3GM than MD3 and a lot less weight. The weight differential may give you some trim issues. The Yanmar is a converted tractor engine so expect the non marine parts to be around for a long time. Might want to pick up a used heat exchanger though a company as big as Yanmar is more likely to have parts long term than a smaller outfit. I haven't had problems getting the few parts needed for my 3GM but it hasn't needed much. The last ones were sold 15 or more years ago so there is always the chance that parts could be getting scarce.

[Wotname]

I have had two 2GM20s and base my observations on these which are the same family as the 3GM30 as many parts are interchangeable.

I have found them to be solid reliable engines. Yes, parts are expensive but coming from a Volvo background, you might be used to the hip pocket haemorrhage when buying parts. There was a time when cracked pistons were an issue and AFAIK, Yanmar said they did get a bad batch for a short period. I'm guessing these have all rectified by now but as you are buying second hand, it is worth remembering. The vast majority of the engines did not suffer this defect. The production ended in Dec 2005 IIRC.

I believe roverhi is in error when stating they are from a tractor origin; AFAIK, they were designed by Yanmar as a dedicated recreational boat engine. I do think spare parts will be around for awhile yet - there are thousands and thousands of these engines still in service around the world. I am still getting parts for the Y series and QM series which finished production in the late 70s and 1980. More about the QM below.

Now for unsolicited advice: I presuming you are choosing a second hand engine for economical reasons and I am assuming you know that changing an engine model usually means lots of work in rearranging engine mounts, exhaust, controls, raw water plumbing, fuel plumbing etc etc. I also presume you know that this is expensive if you are paying someone to do it. Therefore I am presuming you are doing this work yourself - otherwise it doesn't pay to re-engine with a used engine as half the cost is in the installation (if paying others).

So if you ARE doing the installation work, you know how to do stuff .

Therefore I can the following suggestion which may save you money or get you a better engine (IMO) or both.

While I have had two GM engines at different times, I am now rebuilding a Yanmar QM series as IMO, they are a far better engine than the GM unless you need the lighter weight of the GM series. Yes, they are much older but bear with me for a moment.

They are used in a thousands of tractors as well as thousands of work boats. They are a slower reving heavy commercial engine compared to the light weight GMs. Max power at 2,800 (continuous at 2,600) compared to 3,600 and 3,400 respectively. A 3QM30 is what I would look for and rebuild it before fitting. I suspect it would be much cheaper than a 3GM30. Rebuilding is a simple job if you already are comfortable with installing engines. This will ensure your re-engine project will be a long term success.

They use wet liners (the GM doesn't) and both liners and pistons are available. At the worst, you need valves, valve seats and guides, liners, pistons and bearings but likely to be less. All should be available at tractor shops as well as marine shops. Perhaps injector nozzles and some injector pump internals. And oh, a can of paint .

Yes, it will take time and some space but if you have both, I can assure you the result will be satisfying. If someone like me can do it, you can .

[sailorchic34]

Originally Posted by Wotname

I believe roverhi is in error when stating they are from a tractor origin; AFAIK, they were designed by Yanmar as a dedicated recreational boat engine. I do think spare parts will be around for awhile yet - there are thousands and thousands of these engines still in service around the world. I am still getting parts for the Y series and QM series which finished production in the late 70s and 1980. More about the QM below.

Pretty sure the original GM series, which did have liners, came from the tractor side. That is the engine block and most parts match 3 cylinder tractor engines of the time. Of course yanmar made different part numbers which makes it harder to cross match. The Marine market is tiny compared to tractor/ light construction equipment.



Yanmar did a VE on the block and went to solid bores / no liners in the late 80's. Along with other minor issues. So the original raw water cooled GM's had liners, the later GM-F's did not. BTW the pistons/ rings on the early GM's are NOT the same as the later fresh water cooled GM's.


I agree that the QM was a really long life engine. Really a lovely engine.



GM's came later with a slightly redesigned block.


A weak point in the GM's is the external steel oil line, which is prone to corrosion about 2 inches in front of the starter. If it looks in any way deformed or dodgy, replace it with Yanmars " newer copper oil lines or DIY for $10 (I Did it DIY) Silver Solder, Never braze, copper joints on oil lines.

[lockie]

Originally Posted by sailorchic34

Silver Solder, Never braze, copper joints on oil lines.

Interesting, can you please explain why?

When mine failed far from home, I had a replacement made up by an agricultural jack-of-all-trades. Maybe I need to redo it to make sure.

Cheers, Graeme

[Wotname]

Originally Posted by sailorchic34

Pretty sure the original GM series, which did have liners, came from the tractor side. That is the engine block and most parts match 3 cylinder tractor engines of the time. Of course yanmar made different part numbers which makes it harder to cross match. The Marine market is tiny compared to tractor/ light construction equipment.



Yanmar did a VE on the block and went to solid bores / no liners in the late 80's. Along with other minor issues. So the original raw water cooled GM's had liners, the later GM-F's did not. BTW the pistons/ rings on the early GM's are NOT the same as the later fresh water cooled GM's.


I agree that the QM was a really long life engine. Really a lovely engine.



GM's came later with a slightly redesigned block.


A weak point in the GM's is the external steel oil line, which is prone to corrosion about 2 inches in front of the starter. If it looks in any way deformed or dodgy, replace it with Yanmars " newer copper oil lines or DIY for $10 (I Did it DIY) Silver Solder, Never braze, copper joints on oil lines.

It is important to distinguish between Yanmar GM engines and GMxx engines. They are quite different!

1/2/3 GM engines were manufactured 1980 to 1983. The 1GM was raw water cooled (RWC) while the the 2 & 3 GM came in two variants - RWC and Fresh water cooled (coolant) - designated as F. The 2 & 3 GM had block liners while (AFAIK) the 1GM didn't.

The GMxx engines were introduced in 1983 and the 1GM10 finished in 2009 while the 2GM20 & 3GM30 finished in 2005. None of these (GMxx) engines had liners.
The 1GM10 was RWC only while the 2GM20 & 3GM30 were available in both RWC and F models.

FWIW, a lot of early Yanmars had external oil lines - YSE, YSB, YSM, QM, GM, GMxx and AFAIK, the SB. They need to be inspected although the QM ones I have seen are not steel. Maybe they were steel at some stage - I just don't know (yet ).

[sailorchic34]

Originally Posted by lockie

Interesting, can you please explain why?

When mine failed far from home, I had a replacement made up by an agricultural jack-of-all-trades. Maybe I need to redo it to make sure.

Cheers, Graeme

When you heat copper tube or pipe over about 700 degrees you anneal the copper section that has been heated. This makes it softer then the adjacent non-heated parts. What happens is when the copper tube or pipe is heated the non annealed section will expand via thermo-expansion into the annealed part at the joint. This causes the annealed copper to crumple and when it cooled, more times then not there will be a leak at the crumpled part.


I have seen this exact thing in brazed 1" copper tubing used in large building hydronic systems. The Contractor had to go back and replaced brazed joints with solder in about 100,000 joints at LUXOR in Vegas back in 1994. This after many leaked.



Soldering at say 450 degrees with 5% silver solder does not anneal the copper, so the copper at the joint stays strong and the tube or pipe will flex / bow out. This is what I did back in 2013 when I rebuilt my 3GM30F and replaced the leaking oil line with copper. It's still leak free with over 700 hours on the clock.



Yanmar has a replacement copper oil line as pretty much all the original steel oil lines will be developing rust about now.

[sailorchic34]

Originally Posted by Wotname

It is important to distinguish between Yanmar GM engines and GMxx engines. They are quite different!

1/2/3 GM engines were manufactured 1980 to 1983. The 1GM was raw water cooled (RWC) while the the 2 & 3 GM came in two variants - RWC and Fresh water cooled (coolant) - designated as F. The 2 & 3 GM had block liners while (AFAIK) the 1GM didn't.

The GMxx engines were introduced in 1983 and the 1GM10 finished in 2009 while the 2GM20 & 3GM30 finished in 2005. None of these (GMxx) engines had liners.
The 1GM10 was RWC only while the 2GM20 & 3GM30 were available in both RWC and F models.

FWIW, a lot of early Yanmars had external oil lines - YSE, YSB, YSM, QM, GM, GMxx and AFAIK, the SB. They need to be inspected although the QM ones I have seen are not steel. Maybe they were steel at some stage - I just don't know (yet ).

I think we are saying the same thing. You are right that the older original 2GM and 3GM was raw water cooled and hand liners as did the optional 2GMF and 3GMF fresh water option. Note that the original gm series engines were called 2gm and 3gm or 2gmf or 3gmF The newer designation 2gm20F and 2GM30F engines were fresh water only and came with solid blocks and a slightly different piston size. This was a slightly redesigned block compared to the original 2gm and 3gm Displacement was a tad larger for the 2gm20 and 3gm30 compared to the original 2gm and 3gm which has sleeves and a smaller diameter piston.


The later 2gm20 and 3gm30 engines has steel external oil lines. That may have been a cost cutting measure, like the lack of liners on the 2gm20 and 3gm30 variations.



That's the fun with the GM series engines. There are two different designs. You have 2GM and 3GM with liners and other small variations and the later 2gm20 and 3gm30 which is a redesigned "cheaper" to produce engine.

[lockie]

Thank you, I will inspect. It sounds like the leaks would be of the nuisance but not catastrophic variety.

Cheers, Graeme

[roverhi]

The replacement for the external oil line has some form of copper whether it's straight copper or something more exotic is anybody's guess. The reason I changed mine out was the exhaust coupling at the back of the heat changer leaked dripping sea water onto the pipe. The rest of the pipe was fine after 10 years. Changed out the old steel for the new copper when I had the engine out on the cabin sole as it was really easy to do and the steel one was pitted and looked close to failure.

[Wotname]

Originally Posted by sailorchic34

I think we are saying the same thing. You are right that the older original 2GM and 3GM was raw water cooled and hand liners as did the optional 2GMF and 3GMF fresh water option. Note that the original gm series engines were called 2gm and 3gm or 2gmf or 3gmF The newer designation 2gm20F and 2GM30F engines were fresh water only and came with solid blocks and a slightly different piston size. This was a slightly redesigned block compared to the original 2gm and 3gm Displacement was a tad larger for the 2gm20 and 3gm30 compared to the original 2gm and 3gm which has sleeves and a smaller diameter piston.
........................

We might be saying the same or we might not be! It might be a subtle difference between USA english and Australian english...

It seems to me that you are saying the 2GM20 & 3GM30 only came in freshwater versions (the 2GM20F and 3GM30F).

I am saying the 2GM20 and the 3GM30 was available as a RWC as well as the freshwater versions thus we have a 2GM20 and a 2GM20F along with a 3GM30 and a 3GM30F.

To make it more confusing (), the 1GM10 was only available as RWC engine.

[sailorchic34]

Originally Posted by Wotname

We might be saying the same or we might not be! It might be a subtle difference between USA english and Australian english...

It seems to me that you are saying the 2GM20 & 3GM30 only came in freshwater versions (the 2GM20F and 3GM30F).

I am saying the 2GM20 and the 3GM30 was available as a RWC as well as the freshwater versions thus we have a 2GM20 and a 2GM20F along with a 3GM30 and a 3GM30F.

To make it more confusing (), the 1GM10 was only available as RWC engine.

I suspect it's that English thingy. Yes Both the GM and GMxx come in Raw water version. I've not seen many of the later in the US though.



Have a great holiday!