Yanmar 3gm30f rpm recomendations

[Adelie]

Originally Posted by Mg451

Hmm maybe I have prop issues too there's no way ill get 3600 rpm..even in neutral I don't think I could reach 3600..I'll try it in neutral but 2600 in neutral she's screaming like a banshee. I feel like 3600 would be self destruct mode. Any recommendations on the tach apps?

Simple tach check is to get a fluorescent light that runs off 60Hz ac shore power or inverter. Put a white mark on the front end crank pulley.
At 3600 you should see 1 mark.
At 1800 2 marks.
At 2400 you will see 3 faint marks

[Cheechako]

Originally Posted by Mg451

Off the top of my head I believe yanmar 3gm30f should be ran at 2500 rpm minimum? I've been running mine at 2100rpm for years now. The boat is on the slow side underpower .for the life of me when I have it up at 2500rpm or more she sounds like she's really screaming! I use diesel weld machines generators and compressors etc in the industrial construction field , I'm no desiel guru but based on theese I feel like even 2100 rpm is just right ( sound ) or even a bit on the high side but tolerable. Perhaps my intuition or my tach is off. Is there a way for a layman such as me to easily check that my tach is correct? And does any one else feel 2500 or more sounds really high? Where do you guys run yours? Thanks
P.s I'm talking running under power for hours on end...

I had 'em in my cat. At high rpm, like 3000-3200 it sounded like I was flying an airplane. No way for me. I repitched my Max Props and ran lower rpm. IIRC I ended up liking about 2200-2300 rpm.
The trouble is they are a wimpy little engine . They named them 3GM30 but they are like an 18 hp engine or something like that... I can't remember.

[RaymondR]

Originally Posted by Cheechako

I had 'em in my cat. At high rpm, like 3000-3200 it sounded like I was flying an airplane. No way for me. I repitched my Max Props and ran lower rpm. IIRC I ended up liking about 2200-2300 rpm.
The trouble is they are a wimpy little engine . They named them 3GM30 but they are like an 18 hp engine or something like that... I can't remember.

Had they been petrol (gas) engines you would probably have had no concern regarding the "high" revs.

Since the power produced by the engine is the product of the torque multiplied by the revolutions there is two ways to produce that power, either high revs at low torque or, low revs at high torque. If you want a low vibration, and consequently smooth running engine you go the high revs route. If you need high torque you go the low revs route. In the 3GM30 Yanmar went the high revs low torque route which, whilst moving away from the more normal diesel engine operating noise spectrum, provide a low vibration unit.

An inspection of the power curve for your engines would show that by over-propping them you prevented them from being able to prevent their full power capability and, in addition, forced them to run at high head pressures and thereby probably considerably reduced their working life whilst reducing their potential power output.

[Cheechako]

Originally Posted by RaymondR

Had they been petrol (gas) engines you would probably have had no concern regarding the "high" revs.

Since the power produced by the engine is the product of the torque multiplied by the revolutions there is two ways to produce that power, either high revs at low torque or, low revs at high torque. If you want a low vibration, and consequently smooth running engine you go the high revs route. If you need high torque you go the low revs route. In the 3GM30 Yanmar went the high revs low torque route which, whilst moving away from the more normal diesel engine operating noise spectrum, provide a low vibration unit.

An inspection of the power curve for your engines would show that by over-propping them you prevented them from being able to prevent their full power capability and, in addition, forced them to run at high head pressures and thereby probably considerably reduced their working life whilst reducing their potential power output.

It's all about how much power you need for sure. Engines aren't designed around the boat, the boat maker just selects one close to what he needs. I have specified diesel engines for work boats. Many engine makers change the advised RPM based on the boat's needs. For instance the same commercial engine maybe be rated at 2200 rpm for continuous use (like a ferry), at 2600 rpm for intermittent use (maybe a fishing boat), and rated at 3000 rpm for recreational use.
Unfortunately Yanmar makes a light duty engine and raise's the stated HP via a high RPM rating.
Personally I want to compare engines at the same rpm via their power curve, not via the maker's label of "HP".

[Shaneesprit]

Originally Posted by Salty Possum

I try to run mine at 2850 usually. I used to run it 2100 but plugged the exhaust elbow with carbon and was admonished by multiple sources that the engine needs to run hotter to avoid carbonization of the valves. I increase to WOT for at least a few minutes once an hour or so. I also started avoiding short operations, running the engine longer after leaving the harbor and starting it earlier upon return in order to bring it to full operating temperature. Is this right? I don’t know. I am not an engineer or a mechanic.

But “full operating temperature” as reflected by the water temperature and the thermostat opening temperature already seems shockingly low to me and well below the point where the oil in my sports car is thought to start doing it job well enough to push the engine so I am now more concerned about operating the engine chronically cold than excessive wear from a higher rpm.

When I was advised to start running my engine harder, it really sounded too fast at first but I got used it and my perception has changed. I burn more diesel of course but even at current prices, it is way cheaper than engine work. I make up for it by making more legs from anchor to anchor without starting the engine at all.

Generally harder is better, but it is to do with BMEP nothing to do with water temperature. Running at idle or with a prop that is to small will have the same effect. and Additional RPM will not help.
In general looking for a minimum of 50% load. and as each prop / hull is different actually listening to the engine is probably more effective than an RPM gauge.
If you know 2100RPM is not enough for your boat due to carbon buildup, then you probably don’t have to run at 2850 all the time. As hard running undoes some of the damage low load running causes.
My Tachó does not work but I wouldn’t think to look at it if it did.

[Wonder]

Our 2004 Hunter36 has a Yanmar 3GM30f and it burns 0.5 gallons (or less) of diesel per hour at its sweet spot of 2,600 RPM.
I allow 1 gallon per hour for safety but it never burns more than 0.5 GPH, and often uses 0.3~0.4 GPH.
When distance motor sailing it is not uncommon for us to run the engine at less than 2,000 RPM.
The only time we'll go over its sweet spot of 2,600 RPM is to occasionally clean out the engine, or for emergencies like making bridge openings, docking in high winds, etc...
I think max RPM may be as much as 3,600 RPM but I'm not sure, I would never rev that high for any length of time anyway, just doesn't feel right.
I much prefer to use sails alone without the sound of a noisy engine, but sometimes the wind is just too light, or the wrong direction, or must make-up time for a favorable current through inlets, or get to a safe spot before dark.
You know how that works.

[NorthCoastJoe]

I run my 3GM30F normally at 2800-3200 for extended periods, it is a bit loud.
At 2400 there is a lot less noise running in flat water.
Every time before we shut down I run WOT for about 30 seconds with a 5 to 10 second wind down to idle speed. I always have enough juice if I need it.

My Pearson 30 prop is matched to the engine, transmission and boat by the prop maker.