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Old 07-07-2022, 17:04   #1
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Yanmar 3gm30f rpm recomendations

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...
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Old 07-07-2022, 17:41   #2
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Re: Yanmar 3gm30f rpm recomendations

Yanmar specs -
Max intermittent (2 hours) 3,600
Max continuous 3,400

Best operational speed is more a functional of your gearbox ratio, prop dimensions and hull type.

With a very clean hull and prop on a very calm day, slowly increase rpm until you reach hull speed (i.e. no further increase in boat speed). This will now be you maximum useable rpm / horsepower for your boat in calm conditions. The differential between this rpm and 3400/3600 is the power buffer you have for adverse conditions.

You can check the tach by using a smart phone tach app, there are a few good free tach apps.
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Old 07-07-2022, 17:45   #3
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Re: Yanmar 3gm30f rpm recomendations

Additionally, if you are correctly propped, you should be able to achieve 3600 with a very clean hull and prop in calm conditions. If not, your prop dimensions are not ideal for your gearbox ratios and hull type or your engine is losing power.
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Old 07-07-2022, 18:01   #4
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Re: Yanmar 3gm30f rpm recomendations

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?
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Old 07-07-2022, 18:29   #5
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Re: Yanmar 3gm30f rpm recomendations

A 3GM30F should run to 3600 in neutral and there is a max rpm limiter on the injector pump / governor linkage.

Even if the limiter has been maladjusted in the past, it is highly unlikely you can damage the engine by going to wide open throttle (WOT) in neutral.

I have had occasion to run a 2GM20 at 3400 for 12 hours or more.

I have only used the "Strobe tachometer (RPM meter)" app by Dmitriy Kharutskiy for an iPhone. I believe he makes an android version as well. Google is your friend, try looking for fan speed apps or strobe tachometer apps.

The free one I use (can upgraded for a few dollars) - https://apps.apple.com/au/app/strobe...er/id831460940
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Old 07-07-2022, 19:24   #6
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Re: Yanmar 3gm30f rpm recomendations

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.
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Old 07-07-2022, 19:32   #7
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Re: Yanmar 3gm30f rpm recomendations

Hmm very interesting I'm gonna have to really try to not let my judgement get in the way and run this mother a little harder then I have just seems so against my judgement.
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Old 07-07-2022, 19:53   #8
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Re: Yanmar 3gm30f rpm recomendations

As far as I am aware no Dino powered engine likes to run cold
And a diesel won’t warm up idling unlike a gas one
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Old 07-07-2022, 19:58   #9
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Re: Yanmar 3gm30f rpm recomendations

At 2100rpm my exhaust is hot and it' ( sounds like in my opinion) its running as hard as any other diesel I've ever encounterd.
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Old 07-07-2022, 20:14   #10
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Re: Yanmar 3gm30f rpm recomendations

If it has been operating around 2,000 for years, it would pay to check your raw water exhaust injection mixing point (elbow etc). These will clog up and restrict exhaust flow to the point where the engine will not reach max rpm. It extremest cases, the engine won't get past an idle.

With normal operation, the engine will reach operating temperature within 5 to 10 minutes but the exhaust downstream of the mixing point should always be cool. If not, you have restricted a raw water flow and this isn't good. One of the first signs of restricted raw water flow is steam appearing in the exhaust when powered up, especially if operating in cold ambient air temperatures.

FWIW, oil temperature takes a long time to reach operating temperature - as much as 40 minutes or more at (say) 3,000. You can measure this with an IR temp gun on the on the oil filter.
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Old 07-07-2022, 22:42   #11
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Re: Yanmar 3gm30f rpm recomendations

I had a 3GM30 in my previous boat. Ran it at 2,750 for years. When it was about 28 years old I re-engined the boat and we installed a hydraulic pump on it to run a pile drilling machine. We ran it at full throttle and about 3,000 revs for six weeks and I was amazed that it survived.

They were also very common on fishing boats running generators and freezers where they ran under high loads for years. Terrific little engines.
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Old 08-07-2022, 08:03   #12
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Re: Yanmar 3gm30f rpm recomendations

Well when I get closer to my hone port I'm gonna turn it up. Perhaps my boats not as slow under power as I always suspected
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Old 08-07-2022, 08:07   #13
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Re: Yanmar 3gm30f rpm recomendations

Any idea what my ol temp and exhaust elbow temp should be at? I replaced the exhaust elbow and piping 600hrs ago so if I am indeed running her cold hopefully it's not too clogged up..also what is the estimated hour lifespan of theese? I rember reading it in a yanmar book a time back and I was surprised I thought it was a low estimated lifespan.guess I misread it. Or misthunk it.
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Old 08-07-2022, 08:08   #14
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Re: Yanmar 3gm30f rpm recomendations

P.s. I also change full synthetic every 100 hrs...
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Old 08-07-2022, 16:09   #15
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Re: Yanmar 3gm30f rpm recomendations

When I run my 3ym30 at 2800 it pushes my 34’ 11,000 pound Beneteau to 6.5+ knots. Going higher doesn’t add much more speed. I top out around 3500. I find myself running 2500 all the time and when I use my infrared thermometer I get good and high engine temps. I also change my mixing elbow every 4-5 years. Easy swap out and I have seen the ramifications of a leaking elbow. So I have witnessed no buildup in the elbow.
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