Yanmar 3gm30f rpm recomendations

[01kiwijohn]

I can get 95% of max rpm underway. Usually, run at 2500.

[bensolomon]

I run my 3gm30f at 2000 rpm and get 6 knots cruising speed with good temps.

[roverhi]

Originally Posted by bensolomon

I run my 3gm30f at 2000 rpm and get 6 knots cruising speed with good temps.

If you are getting 6k at 2,000 rpm there is something seriously wrong with your knot meter or the tachometer. How much rpm do you get at full throttle. Engine should run to 3600rpm in flat conditions. If it bogs down and won't get to 3600rpm you are over propped and need to decrease the pitch or shave some off the diameter.

I've run my 2GM at 2800rpm for three days straight and it didn't sound like I was pushing it. Ran my 3GM at the same rpm for two days straight and it sounded fine. The days of the heavy slow turning engines died many years ago. These newer engines are designed to run at much higher rpm than the older engines like the Volvo MD Series and their follow on models.

The boat with the 2GM carboned up the exhaust elbow in under a 150 hours. Owner died, boat title ended up in court with the heirs for several years. Some good samaritans periodically ran the engine at idle to keep the juices flowing. When I moved the boat to it's new slip ended up burning up the plastic muffler because of restricted water flow from the mixing valve.

[Pendragon35]

My 3gm30F has 700 hours. I change the oil and fuel filters regularly and the air filter. It will idle past 3600 but I don't push it past that. It easily drives the boat to hull speed about 2800 rpm. Boat is a modified full keel Alberg 35.

[chris mac]

We have run out 3gm30f engines at 2800 rpm for 10 hours per day for 12 days in a row. And on one crossing for 36 hours straight.
It runs great and has no problems. Periodically I bump it up to max revs(about 3300) for a half hour or so. That is on the advice of a diesel mechanic friend.

[Mg451]

This is all good news any ideas on how many hours these 3gms usually get?

[CAVOK]

Check your rpm against another tachometer. I thought I had a problem with an older Yanmar, but found out my tachometer was under reading by several hundred rpm. It’s a good first step to try.

[Mg451]

I got that app I'm not sure how to use it though it's a strobe you set the rpm on the app. I guess I make a mark on the flywheel and the strobe and the mark will " line up" at the proper rpm? I've also converted y belts and have a balmar
Flywheel cover for the big flat belt.

[chris mac]

Originally Posted by Mg451

This is all good news any ideas on how many hours these 3gms usually get?

Ours have over 9000 hours. A mechanic is in the process of cleaning them up and putting them back together. Not a full rebuild. Compression is still good and he figured another 10 years or so before needing any real work.

[CAVOK]

I’m not sure the best way of confirming the correct rpm but I’m sure others or google will give you advice.
It was just that I found that our tachometer was under reading substantially & that our faithful old Yanmar was actually quite ok. I have a different boat with a new 57hp Yanmar & love the brand. Totally reliable

[bensolomon]

Originally Posted by roverhi

If you are getting 6k at 2,000 rpm there is something seriously wrong with your knot meter or the tachometer. How much rpm do you get at full throttle. Engine should run to 3600rpm in flat conditions. If it bogs down and won't get to 3600rpm you are over propped and need to decrease the pitch or shave some off the diameter.



I've run my 2GM at 2800rpm for three days straight and it didn't sound like I was pushing it. Ran my 3GM at the same rpm for two days straight and it sounded fine. The days of the heavy slow turning engines died many years ago. These newer engines are designed to run at much higher rpm than the older engines like the Volvo MD Series and their follow on models.



The boat with the 2GM carboned up the exhaust elbow in under a 150 hours. Owner died, boat title ended up in court with the heirs for several years. Some good samaritans periodically ran the engine at idle to keep the juices flowing. When I moved the boat to it's new slip ended up burning up the plastic muffler because of restricted water flow from the mixing valve.

I won't get 6 knots with the tide against me or any wind on the nose. In any "adverse conditions" she'll drop to 5.x knots at 2000.

I measure SOG due to having an old paddlewheel knot meter.

[fred4936]

Somewhere I heard (maybe from CF) that I should run the engine at 80% of it max RPM. The plate on our 3GM30F says 3400, so I cruise at around 2700. Seems that it will run forever at that RPM. But I will check the elbow this winter, and do the tachometer check per this thread.

[Mg451]

Ran her at 2700 for 4 hrs today actually didn't sound much higher then 2100. But deff didn't sound unhealthy.. thanks for all the input.

[hugosalt]

FWIW... I run my 3GM at 2500-2800 for hours, with 36 hours being longest.
Sometimes will run around 3000 but not for long.
Pushes my 30 fter, about 10,000 lbs all in at hull speed when bottom clean and water flat.
I will occasionally run all out (3500?) in neutral for a minute or so before shutting down,
think I read was recommended in manual.
Boat/motor is 37 years.
Used to check my original mixing elbow every few years and was always clean,
few years ago installed a nice shiny stainless steel elbow and keep original as spare.
Sail boat in winter (30 to 40 degrees F) and starts up with no issues.

[hpaabor]

I had the 3GM F on a 35 foot sailboat for almost 30 years. I did the intracoastal a couple of times. I cruised at 2200 with a Campbell sailor prop that gave me between 5.5 and 6 knots. The motor seemed happy and I got great fuel economy. When I looked into buying a newer bigger boat I noticed that a number of people had had to replace new Yanmars because the exhaust could not cope with the heat generated at running 2800 + which some seemed to prefer.