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Yanmar 3QM30 Power Curve

J

jdgreen

Jay Green
If anyone has a 3QM30 hp vs. rpm curve or data points I would like a few of the data points from mid to max rpm.
 
Thanks, Jim and June. As fate would have it, a friend dropped by today with an OLD shop manual that confirms your numbers.
 
Jim
On my 3qm30 my cruising RPM is about 2200. I can run at 2400 but not for long periods. I'm turning a 3 blade 16 x 11 prop. I,m also turning a 100 amp alternator. I was just wondering what your configuration is that you can turn those higher RPMs?

Jim
 
Has your tach been calibrated? The power curve is for a three bladed prop and comes from the factory manual. Running a diesel engine at reduced rpm's for long periods of time can cause carbon buildup and reduce engine life.
 
can anyone tell me how the yanmar 30 copes with pushing a 17000lb + boat through rough seas as opposed to the perkins.

Practical sailor magazine suggests that "for adequate power in anything other than a flat calm, about 1-1/2 horsepower - at the engines normal cruising rpm - per thousand pounds of displacement is necessary." hence about 25.5hp is required for an unladen 382.

Talk about cutting it close!!!
 
The Yanmar was fine pushing the boat uphill from Mexico to Northern California. It's a good, strong motor!
 
If you are interested in how much power your engine is really developing, a good rule of thumb is 10Hp per gallon per hour.

If you burn 0.7 gal/hr, the engine is producing approximatly 7 Hp. Physics is physics.

Bill Buebel
 
You're starting with the wrong number. You know what your fuel consumption is, you don't know what the horse power is.

Where did it come from? Look at the power curve of any small engine, gas or diesel. The specific fuel consumption will be about 0.5 to 0.6 pounds per horse power hour at the rated power. At reduced power it will be a little more.

Gas and diesel is about 6 pounds per gallon. Do the math, 0.1 gal / hp / hr is close enough to estimate the actual hp being developed.

Don't make the mistake of assuming that your engine is developing a certain hp because the curve says so. That curve is what the engine can develop.

Bill Buebel
 
I was wondering if anyone could help me.. I'm looking for a engine manual for a 3QM30 Yanmar motor..I wanted it for to find out the information on how to remove and replace cyclinder heads.. Thanks
 
I have the manual and can copy the pages you need.

Call me this week at 410-765-4037, and we can find out what you need and when

Carl Miller 382 Hull002 SV Courante
 
Can anyone here tell me what angle the 3qm30 will go to i.e is it 10 degrees or more. without changing the sump. thanks
 
Hi for Carl Miller
I am in Auckland NZ and would love to have a copy of a 3QM30 manual,or at least the eng.data and installation fact sheet.
The local dealer is less than helpfull.
Would be happy to pay for it.
Best regards
Kurt

on9669@hotmail.com
 
<div>This thread is almost 5 years old (July 2001!!) and the poor guy Bill Burton that started it never got what he really asked for(he got some data, though) So for the record, and anyone else that might find it useful, I am posting an image of the 3QM30 Performance Curves from the mnanual.

The discussions about the prop selection may be aided by this too.

I hope you can download an attachment-- I haven't done that yet on the forum.

Carl Miller
SV Courante 382 Hull002 Annapolis MD

<center><img src="http://morgan38.org/discus/icons/attachment_icon.gif" alt="3QM30Performance Curves"></center></div>
 
Some time ago I mentioned a 'rule of thumb' of .1 gallon per hr per horse power to calculate the actual power being generated by an internal combustion engine. For example, the power required at cruise.

I was asked where this came from and asked to show the math. Thanks to Carl Miller in his post of 31 January, 06 I/we now have a 'specific fuel consumption' curve for the 3QM30 engine.

To do the calculation we require the following data.

SFC = 190 gram/hp/hr, from the data
1 Kg = 1000 gram
1 lb = 0.4536 Kg
1 gal = 7 lb, Approx wt of diesel fuel

(190 g/hp/hr) * (1 Kg/1000 g) * (1 lb/0.4536 Kg) * (1 Gal/7 lb) = .06 gal/hp/hr (approx)

The reciprocal of this is approximately 17 hp*hr/gal. When multiplied by the experienced gal/hr consumption, the dimension 'hr/gal' is cancelled and the result is the engine hp for the period. That is 1 gal/hr means the engine was running at 17 hp.

That's the math given the advertised Specific fuel consumption.

By using the advertised Fuel consumption, from the same performance curves we get a different answer.

From the data, at 1800 rpm the hp is 22 and the fuel consumption is 5 liters/hr or 1.8 gal/hr. The math here is trivial and yields .08 gal/hp/hr and 12.2 hp*hr/gal.

This value is closer to my 'rule of thumb' and is more believable to me. This rule of thumb is also mentioned in SKENE'S ELEMENTS OF YACHT DESIGN and is suggested to be used for both gas and diesel and is probably more accurate for gas engines.

I know this is somewhat complicated, but I was asked to 'do the math'. All I was trying to do was show that there is not a direct correlation between rpm an power. The output curve shows the max hp at a given rpm. The actual hp at a given rpm can be anywhere between zero and max for that rpm.

Fair Winds and Cheap Diesel

Bill Buebel, M381 SHADOW
 
Interesting but a slip there. 5 l/hr is 1.3 us gal/hr not 1.8, so the figure is .057 gal/hp/hr. I wonder if one might take the continuous power at 1800 of 20 and 4.75 l/hr which still gives .063 usg/hp/hour. Even .06 gal/hp/hr is a bit cheaper than .1. Chris_gee
 
I know this is an old thread, however, math problems are fine, but What is the actual usage of these engines.
If you have a 33hp Yanmar and a 45 gallon tank, how far or many hours can you actually go pushing this boat 382?
All engine drink a little differently, but I just would like to know about how far you guys have actually gone on a tank.
Thanks,
Kajun
 
I understand that, but was just curious about how many miles I could expect on a tank. Let say average day a cruisin". 250 to 300 or 200 t0 250?
thanks again
 
Larry: I have a 4-108 but, there shouldn't be much difference in the fuel consumption of either engine. The question that you need to ask, is gallons per hour. My Perkins has never done better that 0.6 gallons per hour and my speed through the water was about 6.3 knots. On one particularly brutal day it consumed over 1 gallon per hour and my speed through the water was between 2 knots and 5.8 knots. The frequence and duration of the waves were difficult for my 30 foot water line. However, when I motor it is normally flat water so I use the 0.6 gallons per hour for planning purposes.

Jay
 
Larry
I have the Yanmar and over the years I've come to figure on 3/4 gallon per hour. That is very general and takes in most conditions from cruising speed in rough water to idling to amp up. Also, if you have the fiberglass, factory installed tank below the cabin sole, it's volume is more in the 38 to 40 gallon range. I recently polished my fuel with 3 gallons in the tank, then filled up to the top with 34.8 gallons from the pump. I would be conservative in my calculations and not count on more than 40 gallons and about 50 hours running time per tank.
 
Jay, I must be doing something wrong. Under power, with no wind help, my 4-108 uses 1 gallon an hour. I have been meaning to have the injectors tuned up. This encourages me to get that done sooner rather than later.
 
Terry, my 4-108 uses just under 1 gallon/hr at 1700 to 1800 rpm and does 6.7 to 6.8 knots on flat water (by GPS).
 
Fascinating. My 4-108 uses 1 gal /hr about, at 1900 rpm, and by GPS I get 6 knots. And the bottom has recently been painted. I suppose you and I may have different props, but I think mine is the standard 16x11.
 
Terrence: I just had my injectors cleaned last winter. I had noticed an increase in fuel usage plus I was getting an increase in black smoke. Based on what I have calculated this year it appears I'm back down to the 0.6 gal/hr. I normally do a calculation at the end of the season.
 
ahhh-that explains it. If I average motor sailing, idling to charge batteries and run the engine driven compressor for the fridge, atter, motoring slowly in and out of harbors, etc. I probably burn 0.6 gpm. If I am running flat out for 24-36 hours, as I sometimes have to do running from Oregon up to Washington with no wind, I burn 1 gph.--?Also, unfortunately, I have blue smoke now, not black smoke. That must mean I am burning up some lube oil, but the oil usage is not excessive and I hate to think of the cost of a rebuild. The engine runs fine, but puts out the blue smoke.

BTW--I lost a flex-plate this summer--what attaches the engine to the transmission--it is found in the back bell housing on the engine. I didn't know it existed. Had I known, I would have replaced it when I replaced the transmission 3 years ago. Anyway, the old springs on the thing finally broke and left me with no power to the transmission. Luckily, I was close enough to home that a friendly mechanic came out and replaced the thing for me.
 
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