2GM20F 16hp what years made?

[Aquah0lic]

Just curious how old this engine could be.

Also why do I see the same engine listed as different HP in various boat ads?

[Vasco]

Very early eighties (I think) to late nineties . I have the Yanmar manual for the 1/2/3 GM's and if I can decipher the code it was printed in 1983. The 2GM hp is shown as 16.

[svHyLyte]

The 2GM20F is (or at least was) rated at 18 hp continuous--20 hp maximum and was around before 1986 as that was when we had one installed in our (then) Cal 2-29. It, together with its 3 cyclinder sybling, are some of the best engines made by Yanmar and, like ever-ready bunnies, just keep going and going. The only thing you'll need on had are spare fan belts, impellors for the water pump">raw water pump; and, a spare mixing elbow as you'll blow through one about every 500 hrs. or sooner if you only use the engine for a short while at a time. The engine we had installed is still going strong (for the "new" owner) and still looks like new (I'm told). Just do the maintenance at 100 hours religiously.

Cheers,

s/v HyLyte

[Aquah0lic]

This one says 16 hp on the tag and I've seen others listed on this site as 13 hp.

Does the F have anything to do with the HP variances?

Also, are there multiple transmission options that came with this engine?

[GordMay]

The “F” designates a Fresh-Water cooled engine.

The 2GMF engine was a 15HP* Fresh-Water Cooled engine c/w 35A alternator, built between 1980 & 1983.

The 2GM20F was an 18HP* (bored out 2GMF) Fresh-Water Cooled engine c/w 55A alternator, built from 1983 onwards.

*Specified HPs are Maximum output. Continuous outputs are 13HP & 16HP, respectively.

[svHyLyte]

Humm... Evidently our vendor BS'd me in re: HP. (He claimed the "20" ment it was a 20Hp max output even though the tag on ours indicated 18. Never the less, it was/is a good engine! (All up in 1986-$7,000 installed!)

Cheers,

s/v HyLyte

[never monday]

The GM series ran from 1980 to 2005. The 1Gm is still in production.
Of the 2&3 GM's there were several variants and HP ratings.
2GM, 2GMF, 2GM20, 2GM20F, 2GM20F-YEU, 2GMD?
The labels on the engines over the years showed different ratings either continuous or max. I've never heard a reason as to why they were changed.
Many parts are interchangeable, but the internals are different.

[Aquah0lic]

Thanks Gord,

I think you nailed it because this one does have a 55a alternator. So, its at least an '83. Is there any way to determine exact year from a casting number or other identifiers?

[Aquah0lic]

Hylyte, what kind of tranny is yours coupled to?

[GordMay]

Currently Yanmar dealers do not have the means to easily cross reference to build date, date of commission, warranty status etc..

[hugosalt]

When I bought my current boat new in 1985, I upgraded the motor to a 3 cylinder
for the extra hp...my 3GMC (c=saildrive) is 22 1/2 hp. I believe this motor was
made 1980-1983 and became the 27 hp when the cylinders were bored.
Hylyte is spot on... great engine ...reliable...mine is raw water cooled which means additional maint. of changing engine zincs from time to time.
Mack Boring , Union N.J. still has some long standing techs who
will spend some time on the phone solving problems and explaining the evolution
of the gm series. Bye the way, whenever I ask is there anything else I can do
besides the usual maint. the answer I always get "just run her hard" prevents carbon
build up I believe. (Mack Boring is US importer/dist for Yanmar.)

[never monday]

Originally Posted by hugosalt

(Mack Boring is US importer/dist for Yanmar.)

Sir,
This is an incorrect statement. Yanmar a Japanese Company has an American Subsidiary in Buffalo grove Illinois. Mack Boring and parts Company is regional distributor for Yanmar marine products.

[svHyLyte]

Aquaholic--

Unfortunately, I don't recall the specifics of the transmission very well. I believe it was a 2.62:1 but I could easily be wrong. It was whatever Yanmar's standard transmission was at the time. We had a 12" fixed 2-blade prop as I recall and got very good performance and fuel economy. The engine easily pushed the yacht to 5-1/2 knots and used less than 1/2 gallon per hour.

Cheers,

s/v HyLyte

[hugosalt]

Thanks Never Monday...
Did not know if Mack Boring was importer or distributor that's why I put "/" between
the two. I would not want to mislead anyone with a incorrect statement.

[popeyepcb1]

Originally Posted by svHyLyte

Aquaholic--

Unfortunately, I don't recall the specifics of the transmission very well. I believe it was a 2.62:1 but I could easily be wrong. It was whatever Yanmar's standard transmission was at the time. We had a 12" fixed 2-blade prop as I recall and got very good performance and fuel economy. The engine easily pushed the yacht to 5-1/2 knots and used less than 1/2 gallon per hour.

Cheers,

s/v HyLyte

what size yatch is the boat u speak of? thinking of repowering with 2GM20