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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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Diesel This is a new forum dedicated to diesel engines and their applicable accessories.


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  #11  
Old 01-26-2013
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Re: Yanmar 3GM30F HP one-hour rating (??)

Great info everyone. Thanks. The boat is a Freedom 36/38. The 38 refers to the "sugar scoop" transom but that probably won't affect LOA that much in relation to power through the water. It is a pretty flat bottom. On the sea trial with new bottom paint, we got it up to speed and it was close to 7 knots but that was without wind, current or swell working against it. I am hoping it is going to be OK, but it's a "sail" boat, yah? Big, diesel guzzling engines are the reason I got out of power boating....

Here's the funny part. The Yanmar contact I made told me that the 3GM30F is a 27HP, 3600 RPM engine, but the plaque on the engine itself says 24HP, 3200 RPM. I remain confused!

Anyway, I do plan to take a diesel engine course but the one recommended by aa3jy is only on the East Coast so I'll have to find something in California. In the meantime, I'm just going to plow right in. It looks like much of the maintenance I can (and should) do myself. The internet is a great thing, too, if I should get stuck ;-)

Cheers!
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  #12  
Old 01-26-2013
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Re: Yanmar 3GM30F HP one-hour rating (??)

Oh, on haul out, it weighed 20,000 lbs, which is pretty close to the specs.
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Old 01-26-2013
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Re: Yanmar 3GM30F HP one-hour rating (??)

Quote:
Originally Posted by gamayun View Post
Oh, on haul out, it weighed 20,000 lbs, which is pretty close to the specs.
Actually your 38's design spec is more like...

FREEDOM 38 sailboat specifications and details on sailboatdata.com

..well within the capability of the Yanmar 3GM30F

Here are some details from the workshop manual:

Model 3GM30
Type: Vertical 4-cycle water cooled engine
Combustion Chamber: swirl pre combustion chamber
No cylinders: 3
Bore x stroke mm(in): 75 x 72 (2.95 x 2.83)
Displacement litre (in³): 0.954 (58.21)

Continuous rating output (DIN6270A)
Output crankshaft speed Hp/rpm (kW/rpm): 24/3400 (17.9/3400)
Brake mean effective pressure kg/cm² (lb/in²): 6.66 (94.71)
Piston speed m/sec (ft/sec): 8.16 (26.77)

One hour rating output (DIN6270B)
Output crankshaft speed Hp/rpm (kW/rpm): 27/3600 (20.1/3600)
Brake mean effective pressure kg/cm² (lb/in²): 7.07 (100.54)
Piston speed m/sec (ft/sec): 8.64 (28.35)

Compression ratio: 23.0
Fuel injection timing degree: b.TDC18±1°
Main power take off: At flywheel side
Front power take off: At crank shaft V pulley side
Direction of rotation - Crankshaft - Counter clockwise viewed from stern
- Propeller shaft (ahead) - Clockwise viewed from stern
Lubrication system: Complete enclosed forced lubrication.
Starting system: Electric and manual

Lubricating oil capacity (rake angle 8°)
Total litre (in³): 2.6 (158.65)
Effective litre (in³): 1.6 (97.63)

Engine weight with clutch (dry) Kg (lb) : 130 (287) Raw water
Engine weight with clutch (dry) Kg (lb) : 138 (304) fresh water

Gearbox
Model: KM3A
Constant mesh gear with servo cone clutch (wet type)
Lub oil: SAE# 10W-30, CC class
Lub oil cap: 0.3 ltr
Dry weight: 11.0kg (24.3 lbs)

Last edited by aa3jy; 01-26-2013 at 03:52 PM.
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Old 01-27-2013
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Re: Yanmar 3GM30F HP one-hour rating (??)

Those specs are close but mine is not a shallow draft. This is more like it: FREEDOM 36 sailboat specifications and details on sailboatdata.com, which doesn't actually specify the HP rating.

Sooo, maybe I am missing something obvious to everyone here but me, but why would the engine plaque say it's a 24 HP when the Yanmar Company and Freedom say it's a 27 HP? I can only assume that the one-hour max rating dictates its upper threshold. Are other Yanmars like this? Anyway, it's somewhat immaterial. I bought the boat. And now lots to learn!
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Old 01-27-2013
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Re: Yanmar 3GM30F HP one-hour rating (??)

One point of caution about RPM gauges. Most of them will give you a faulty reading, either because they are off, or calibrated incorrectly. I checked the RPM gauge on our boat with a meter at the crankshaft pulley and it turned out to be reading 380 RPM too low. So running at max RPM would be a short lived experience, followed by an engine rebuild.
In 30 years of working with diesel engines, I haven't found an accurate gauge yet. They are all off, some more than others. Beware.....
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Last edited by bjung; 01-27-2013 at 06:30 AM.
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Old 01-27-2013
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Re: Yanmar 3GM30F HP one-hour rating (??)

Quote:
Originally Posted by gamayun View Post
why would the engine plaque say it's a 24 HP when the Yanmar Company and Freedom say it's a 27 HP? I can only assume that the one-hour max rating dictates its upper threshold. Are other Yanmars like this?
It's not inconsistent - there's limited space on the rating plate, and the 'continuous' figure is correct, and safe. The manual has more space to expand on that with the 1-hour rating. From experience with marketing departments, they will naturally insist on showing the "best" number, caveats aside. marketing wrote the spec sheet, but the engineers designed the plate that went on the motor.

My previous 2GM20F and current 4JH2TE both had/have continuous and 1-hr ratings. And I've never needed to run either above, and seldom at, the continuous rating. (Until I re-pitched my Maxprop last spring, I could not even get the 4JH to reach its continuous RPM rating, but that's a different discussion). Consider the one-hour limits a nice cushion for really bad conditions.
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  #17  
Old 01-28-2013
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Re: Yanmar 3GM30F HP one-hour rating (??)

One simplified explanation of the 24/27 hp ratings is that the HP output of an engine is directly related to the RPM. HP rises with RPM up to a max, then tails off at the very end of usable RPM range or redline (usually). At 3400, your engine is producing 24 hp, and if you push the RPM's to 3600, it is putting out 27 hp. The problem is that Yanmar does not want that engine to be run at 3600 for any long periods. Therefore, it gives it a max rating of the HP produced at 3600, but also gives the max generally usable output as 24 HP at 3400 which can be run all day. Technically it can produce 27, but you can only expect to use 24 for regular use. If you are cruising at, say, 2000 RPM,. the engine will be producing a much lower HP (perhaps 16-18) and you can look at an output graph for that engine and see just what the output is at each RPM level.
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  #18  
Old 01-28-2013
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Re: Yanmar 3GM30F HP one-hour rating (??)

I have a 3gm30 on my Caliber 33 and would never run at 3400 rpm "all day". I tend to run at around 2800 but that is well above the "max distance gained per gallon of fuel burned" rpm's - That is somewhere around 2000 rpm's.
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Re: Yanmar 3GM30F HP one-hour rating (??)

oh and another vote for mack boring's diesel course. They ask what engine you have in your boat and then provide you with THAT SAME EXACT ENGINE to work on for the 3 day course. You will never again get such a good view of the back side of your engine
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Old 01-29-2013
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Re: Yanmar 3GM30F HP one-hour rating (??)

Quote:
Originally Posted by sck5 View Post
I have a 3gm30 on my Caliber 33 and would never run at 3400 rpm "all day". I tend to run at around 2800 but that is well above the "max distance gained per gallon of fuel burned" rpm's - That is somewhere around 2000 rpm's.
Around 2450 +/-
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