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**Wotname** · 18-04-2020, 00:35

Does anyone know how to determine the manufacturing date of a Yanmar 2QM20H engine?

The parts book shows two part numbers for the head gasket with a break date of 8/83 and two part numbers for a ring set with a break date of 3/78.

I have been unable to find a date on the engine or a serial number except for a serial number plate on the injector pump. I don't know if this number applies to the parent engine or just the injector pump? I also don't know how to determine a manufacturing date from this number.

Any ideas???

To complicate it slightly more, Mack Boring lists the engine date range of 1975 to 1980.

I haven't found any date reference in the service manual but it is possible I have missed it.

**StuM** · 18-04-2020, 01:56

Is it original to the boat? If so, when was the boat built?

**GordMay** · 18-04-2020, 02:11

2QM20 (1975 - 1980)
Engines with serial numbers 0001 - 0030 were prototypes and may require different parts. Engines with serial numbers 80001 - 80930 and 81131 - 81180 were also different from the primary production models and may require different parts. Engines with serial numbers 80931 - 81130 and any serial number higher than 81181 will use standard 2QM20 parts.

See ➥ https://shop.toadmarinesupply.com/ma...entification++

And ➥ https://shop.toadmarinesupply.com/ma...e&engine=2QM20

**Wotname** · 18-04-2020, 02:48

Quote:

Originally Posted by GordMay

2QM20 (1975 - 1980)
Engines with serial numbers 0001 - 0030 were prototypes and may require different parts. Engines with serial numbers 80001 - 80930 and 81131 - 81180 were also different from the primary production models and may require different parts. Engines with serial numbers 80931 - 81130 and any serial number higher than 81181 will use standard 2QM20 parts.

See ➥ https://shop.toadmarinesupply.com/ma...entification++

And ➥ https://shop.toadmarinesupply.com/ma...e&engine=2QM20

Thanks Gord. That is very helpful but.......
I have been unable to locate the serial number so far - apart from a number on the injector pump (D1407) and that doesn't fit into the scheme of numbers as suggested by Toad.

Mind you, it looks me months before I located the serial number on the YSE 8.

Any ideas on whereabouts to look closer?

**Wotname** · 18-04-2020, 02:51

Quote:

Originally Posted by StuM

Is it original to the boat? If so, when was the boat built?

No boat, engine was sourced from under a house! No idea what boat it had been previously fitted to.

**GordMay** · 18-04-2020, 02:54

According to Toad Marine (previous link):
"Most engine model designations are on an engine data plate, on the front or the top of the engine. Some older engines have the data plate on the adapter plate between the engine and the gearbox ."

**Wotname** · 18-04-2020, 03:07

Quote:

Originally Posted by GordMay

According to Toad Marine (previous link):
"Most engine model designations are on an engine data plate, on the front or the top of the engine. Some older engines have the data plate on the adapter plate between the engine and the gearbox ."

I should have explained that I have already located the data plate but it doesn't include a serial number.

In a like manner, my YSE8 has a similar looking data plate designating the model / rpm / hp etc while the serial number was stamped into the crankcase quite some distance away from the data plate. It was more by chance that I happened upon it.

To date, I have no such luck with the 2QM20

Boatwright · 18-04-2020, 09:35

Boat from under a house?

1) Considering the external signs of long neglect, I'd take off the valve cover and the oil pan, make sure the engine turns over freely, and if there are signs of internal corrosion, get comfortable with your new boat anchor.

2) Even if the engine passes the above tests, parts for older engines can be hard to find and expensive.

3) Also, unless you have a big kit of tools and access to a machine shop this is not an amateur job.

**Wotname** · 18-04-2020, 16:52

Quote:

Originally Posted by Boatwright

Boat from under a house?

1) Considering the external signs of long neglect, I'd take off the valve cover and the oil pan, make sure the engine turns over freely, and if there are signs of internal corrosion, get comfortable with your new boat anchor.

2) Even if the engine passes the above tests, parts for older engines can be hard to find and expensive.

3) Also, unless you have a big kit of tools and access to a machine shop this is not an amateur job.

The engine was under the house, not the boat. The boat had sunk awhile back.

But I'm sure the engine will OK, as the guy who sold it said, it's only dirty on the outside. He also explained that the oil in a diesel engine goes black when the engine is worn out but as you can see the oil in this engine is still (almost) white. So it must be pretty good.

He also explained the reason it won't turn over was because it still had good compression. When I asked about the little bit of rust on the rocker gear he said the was normal because these parts are at the top and the oil drains away from them. He said it will disappear after I run it for a few hours and the white oil will wash it off.

Tools aren't a problem, I have a couple of crescent wrenches and a hammer. If I need a bigger hammer, I can borrow one!

OK, the stuff above is in jest, I have actually disassembled the engine except for removing the liners, that is this weeks job (just gotta make a removal tool first).

Nevertheless, I would still like to find the serial number!

lelolay · 18-04-2020, 18:58

They are all the same tractor engine. If I remember corecthly on the starboard side of The block or on top of the engine starter there is a number. Go to a tractor supply parts an have them try to give you the year an model. there were 3 engines marinized. 2Qm20 2qn20f an the 20H. Another soource of supply is a semi refrigerated truck the big one with the big unit in the front they have parts for them an if you take the block to them they can also identify. (Semi= the trailer behind a highway tractor) Sorry , Im getting old no longer memory working that good. I have had all 3 of them. Excellent engines.

**Wotname** · 18-04-2020, 21:21

^^ Thanks lelolay, I will look harder in the areas you mentioned.

And yes, the QM is a derivative of the 2TR20 tractor engine as fitted to the YM2000 tractor. Unfortunately these Yanmar tractors weren't all that popular in Australia so not so many tractor parts available here.

**Wotname** · 19-04-2020, 23:59

Update - I believe I have found the location of the serial number (thanks in part to leolay). It is stamped into the casing adjacent to the data plate which seems a reasonable place for it. It was well covered in paint and rust!

BUT...

It very difficult to read; you could say almost impossible!

Any ideas how to extract a stamped number from a very pitted cast iron surface.
Penetrant dye?
Some sort of magnetic flux and iron filings?
Some better (easier) way?

**GordMay** · 20-04-2020, 01:51

When a number is stamped into a metal object, the metal underneath the number is compressed and hardened. Even when the number is ground off, this hardened area may still be present. By applying an acid solution, the metal can be slowly eaten away and the number may reappear. This is commonly referred to as “raising the serial number”.
The surface should be cleaned, and brought to a high-gloss finish, even if some irregularities exist. The use of sandpaper or an emery cloth in 320, 400, and 600 grit is recommended to achieve the glossy finish. Use a cleaning solvent to remove all traces of oils, grease, or other substances that will prolong the etching process. Alcohol, acetone, methyl ethyl keytone (MEK), carbon tetrachloride, and gasoline all provide good results.
The etching reagent is a modified Fry’s reagent[*1] that is comprised of concentrated hydrochloric acid, distilled water, and crystalline cupric chloride. The reagent is made in a controlled laboratory environment, where it is commonly used to recover serial numbers that have been removed from firearms.
Using a cotton swab, apply the reagent to the polished area slowly, in a back-and-forth motion over the surface. It is not necessary to apply pressure to the surface. Swabs comprised of cotton batting rolled onto applicator sticks (such as those found in laboratories) make suitable swabs for applying the reagent.
Monitor the progress of the etching process to ensure the quality of the characters that appear and be ready to stop and neutralize the etching by flushing with water.
In addition to the chemical etching process, electricity can be used to expedite the process. Making the surface the positive pole of a low DC circuit (a 6- or 12-volt battery), and using the swab as a cathode or negative pole markedly speeds up the metal removal. This process is best applied to harder steels such as motorcycle and vehicle frames.

Fry’s Reagent ➥ https://etchantstore.com/product/frys-reagent-250-ml/

Recipe: – Fry’s Reagent
40 mls of hydrochloric acid
5 g ferric chloride
30 mls water
25 mls of ethanol or methanol

"Serial Number Restoration (Forensic Testing)"
➥ https://cts-forensics.com/reports/38251_Web.pdf

**Wotname** · 20-04-2020, 05:08

Crikey Gord, I never realised it was so easy

.

More seriously, thank you - I now know what to research and how learn a new skill i.e. raising the serial number.

It appears there are a couple of ways to skin this cat so it might be time to experiment a little on some scrap pieces of cast iron. Some of the reagents could be hard to source locally though.

It will likely be awhile (i.e. weeks) but I will report back with the outcome.