2gm20f RPM

Dec 14, 2009
37
Hunter 29.5 Buffalo
What would be considered the maximum rpm you should operate this engine and is there an optimum rpm?
 
Jun 16, 2011
173
Catalina 350 Rock hall
We run ours around 2600 cruising
And wide open would be about 3200
2600 is were it seems happiest any faster it seems more noise than speed
 
Nov 6, 2006
10,103
Hunter 34 Mandeville Louisiana
Maximum continuous RPM for that engine is 3400 RPM The Yanmar tachometers are notoriously not accurate, so if you are concerned, a hand held laser tacho is good for getting real readings from which, you can understand what RPM you are running when your tach says X.. http://www.amazon.com/Signstek-Prof...d=1407797013&sr=8-5&keywords=laser+tachometer
The engine needs to be run no less than 2600-2900 (when you are running continuously) to keep the carbon out ..
 
Dec 14, 2009
37
Hunter 29.5 Buffalo
Thanks, recently ran mine @ 3000 for 4 hrs, it seemed ok but I wanted to check, wasn't quite wide open.
 
Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
The motor is rated at a max RPM of 3600 and the recommended cruising RPM is approx. 70-80% of the max rating (2500-2900).

We always try to find its sweet spot to minimize the vibration.

These values are only guidelines. If you don't have the proper sized prop then they really do not mean much.

Your engine should be able to reach 3600 in gear. This also assumes that you have a clean bottom and prop.

We run our engine at 2800-3000 on a regular basis. If I was going off shore or coastal cruising I would run the engine at lower RPM's to optimize my fuel consumption.
 
Oct 29, 2005
2,362
Hunter Marine 326 303 Singapore
I find that if I've a clean bottom and prop and shaft clean as well, I can do ultimate max of 3500rpm IF the engine is warmed up gracefully and I inch up the rpm by 200rpm/10 mins interval. I swing a KiwiProp 16" x 18deg. I normally cruise between 2600-3000 rpm.
 

Blitz

.
Jul 10, 2007
709
Seidelmann 34 Atlantic Highlands, NJ
The Yanmar tachometers are notoriously not accurate, so if you are concerned, a hand held laser tacho is good for getting real readings from which, you can understand what RPM you are running when your tach ..
So very correct. Make a chart or replace your tach so you don't do damage. My 3GM CURRENTLY records as follows (your results may vary):

Tach variations:
Shown Reading vs. Actual
700. 880
1000. 1150
1250. 1560
1500. 2032
2000. 2450
2250. 2885
2500. 3135
2600. 3260
2800. 3550

These results will most likely change over time.
 

HMT2

.
Mar 20, 2014
900
Hunter 31 828 Shoreacres, TX
On what part of the engine would you shoot the laser tach?
 
Oct 29, 2005
2,362
Hunter Marine 326 303 Singapore
Stick the tachco reflector on the large crankshaft pulley.
BTW my Yanmar 2GM20F tachco reads on average 50rpm higher than the handheld.