How do I determine which model of Yanmar?

[Jdege]

I have a boat with a Yanmar diesel. It came with a user manual for the Yanmar 1GM10/2GM20(F)/3GM30(F)/4HM35(F).

I know which engine I was told was in it, but ignoring what I was told, and ignoring the manual, how can I tell which engine I have, just by looking at the engine?

And if your answer is to look at the label on the top of the engine, I'm afraid that's exactly where it's most natural to put your foot when you climb down into the engine compartment, and it's written to the point of illegibility.

[Wotname]

Originally Posted by Jdege

I have a boat with a Yanmar diesel. It came with a user manual for the Yanmar 1GM10/2GM20(F)/3GM30(F)/4HM35(F).

I know which engine I was told was in it, but ignoring what I was told, and ignoring the manual, how can I tell which engine I have, just by looking at the engine?

And if your answer is to look at the label on the top of the engine, I'm afraid that's exactly where it's most natural to put your foot when you climb down into the engine compartment, and it's written to the point of illegibility.

I would simply count the number of cylinders i.e. count the number of injectors.

The first number in the model identifier is the number of cylinders.

[Wotname]

Then I would see if it was coolant cooled or raw water cooled. The "F" signifies coolant cooled (F = freshwater). Absence of "F" is raw water cooled.

[Wotname]

If these ideas aren't enough, then post a couple of pictures and we will soon tell you.

[Celestialsailor]

You could always look at the manufacturers plate on the engine.

[AA3JY]

A picture or two would be most helpful...👍

[FabioC]

Just curious... I knew that the first digit is the number of cylinders, but what do the double digits after the letter stand for? HPs?

[roverhi]

The second set of numbers is just a number that Yanmar thought would catch your attention possibly the actual hp rounded up. The 3GM30 makes something like 27hp and the 2GM20 around 16hp so it's not the actual hp produced.

The letters are Yanmar's model designation though there is no logical progression of the model letters. Yanmar's earliest marine engine I think was the YM series followed by the QM then the GM. The HM may be the logical successor to the GM series.

[George DuBose]

[QUOTE=Jdege;3380011]but ignoring what I was told, and ignoring the manual, how can I tell which engine I have, just by looking at the engine?

why would anyone want to ignore a manual? The written word is a good thing.

Does the young generation no longer learn to read? I know my sons don't...

[NorthCoastJoe]

To add to the mix: Yanmar 3GM30F ... 27 HP peak, 23 HP continuous.

[notiesbob]

Isn't the tag engraved/embossed? If it is wipe down the tag and swipe a marker across it to fill in the engraving and wipe of the excess to expose the info. You could also take cell photo of it so you can blow it up.

[billgewater]

Surely the user manual will have schematics for the engine. I know the manual covers 1GM, 2 GM and 3 GM models all together, but the manual does have diagrams of all three.
If single cylinder, it's near guaranteed to be a 1 GM. The 1 GM will be raw salt water cooled i.e. no header tank or heat exchanger and will probably have a Kanzaki gearbox. Near the oil filler will be a single thin pipe that comes up from the high pressure pump then around to the single injector.

Whatever the outcome, become as familiar as possible with these engines and they will give a great service life but they do require proper maintenance.

The 1 GM models require regular replacement of the zinc anodes which protects the salt water cooled engine block. (found, sort of) under the injector. The exhaust manifolds also don't last very long and are expensive to replace. Consider a SS one.

The instrument panels are also given to failure as the wiring is not really high spec. Yanmar parts are often exorbitantly priced so shop around. e.g. the alternators are usually standard Mitsubishi and are repairable.

Also, if your boat is over 30 ft long then a 1 GM would probably provide inadequate power. The 1 GM is really for very small displacement hulls.

If still confused, ask any older boat owner around the marina. Yanmars are ubiquitous.

[Wotname]

Originally Posted by roverhi

...............

The letters are Yanmar's model designation though there is no logical progression of the model letters. Yanmar's earliest marine engine I think was the YM series followed by the QM then the GM. The HM may be the logical successor to the GM series.

FWIW, here is a list containing the common Yanmar models but there are earlier engines that pop up every now and then.

[Wotname]

Originally Posted by billgewater

.........

If still confused, ask any older boat owner around the marina. Yanmars are ubiquitous.

Very true and some of the Yanmar 'speciality' lifeboat engines have unusual model designators.

Pictured is another unusual (to me) Yanmar engine - a 2SX. Check the power lever arrangement, the individual injection pumps and the robust decompression lever.

[chriswheat]

My 3GM30F had an identification plate with model & engine numbers glued to the front of the cylinder head but it fell off recently, yours might still be there. Also the engine number is stamped into the block just above the oil pan toward the front of the engine, port side I believe. The engine number will tell all.