Yanmar 2gm20 fuel Issue

[dfischer]

I have a new-to-me Hunter 326 with the above engine and standard 2-blade prop. The fuel gauge does not work but the hour meter does so I have been trying to determine how much fuel per hour the engine burns. I filled the tank, noted the hours, and motored on and off for a month or so until I had 25 hours of running time. Word from the PO suggested that I would use about 1/2 g. /hour, but I was only able to get 3 1/2 gallons back into the tank.
I appreciate that mileage depends greatly on energy demand and I generally don't run above 2000 rpm, but a burn rate of 1/2 L/hr seems totally unrealistic. Is anyone getting anything close to this?
The only thing I can think of is insuring that the tank is, in fact, full. It's a translucent plastic affair partially accessible by the port stern hatch. Does anyone have a quick procedure for determining the level of fuel in these tanks without spilling diesel into the bilge?

Thanks for your input,
Doug

 

[Deleted member 117556]

The 2GM20F burns about 0.4 -0.5 gph but I never run it as low as 2,000 rpm. Max rpm in gear is about 3,600 so I run at 2,800-3,000 as a cruising speed. I can't imagine that 2,000 rpm is good for the engine as that is slightly more than idle. My new sender and new fuel gauge have never worked so we use engine hours and it is very accurate @ 0.4 gph
bob

 

[mz4wheeler]

Set a high candle power flashlight on top of the tank to illuminate it. Fuel level is obvious.

 

[Ken13559]

My 2gm20f average 2.1L/Hr.

 

[mz4wheeler]

This is a fuel consumption graph of a 2GM20F. To hit 1/2 Gal/Hr, I always do 2600 RPM. If you were just doing 2000 RPM, it is conceivable to get your reported fuels consumption. Remember, it is only just a 16-18 HP engine.

 

[whatfiero]

My 30' Hunter burns 5 gal a year or so I thought I add a jug of fuel every spring and use my engine every other weekend 6 months a year and every wed night for racing add 5 gal and good I keep 1 gal in an old rum bottle in bath under sink for emergency . no one has ever done diesel shots yet

 

[Benny17441]

It takes a while to figure out what our full mark is when pumping fuel. Do not rely on a single fill to calculate the burn rate. Small discrepancies due to disparate fillings, temperature changes, unusual factors will weed themselves out after a good number of fillings. The most practical way is to calculate and average figure based on the way we individually motor our boat. Folks that use extensive warm up and cool down periods while idling the engine may get better burn rate figures but it does nothing to compare your figures with anyone else's. We have narrowed down the burn rate of our 2GM20F to 0.4 GPH but we still use 1/2 GPH when engaging in calculations of available remaining fuel in the tank with other factors to reach a certain destination. Besides the unusable volume of fuel and the emergency reserve over estimating the burn rate to 0.5 GPH facilitates calculations and adds an extra margin of safety. Going for a day sail with half a tank of fuel will not require much calculations but navigating an overnight passage to the next available refuel opportunity requires a more precise knowledge of available fuel, speed and conditions. Knowing when to trade speed and time for fuel can be crucial. The burn rate by itself denotes nothing but it is a tool that when used properly will insure you have the fuel for the safety a running engine brings to the table. Have never ran out of fuel using calculations based on burn rate.

 

[Deleted member 117556]

I agree with Benny - we use .5 gph when estimating but actual is .4 @ 2,800-3,000 rpm. The graph above is interesting but not at all what I have seen from my 2gm20f over the past 3.5 years.

 

[MitchM]

what ever you do, don't run out of fuel. it will be a bear to bleed the system and get the engine started again after you've filled the tank.

 

[Skipper]

I use the how-many-hours-vs-gallons-taken routine. I started doing it the last couple of fills. Am measuring 3.6 hours per gallon, or .278g per hour.
Universal M18, 2 cyl, 35ci, 14hp.
I run at 2,200 rpm, which is at the bottom of the recommended cruising range. Speed at rpm ranges depending on conditions, but typically 5+ knots. More throttle only increases speed slightly, to maybe 5.8 knots top, so no need.
Boat is 30 feet, 10k lbs wet.
So I get in excess of 20mpg statute.
From research, this is about the most fuel sipping motor in existence.
However, I like to brag away about my boat, and this method is not scientific and does not account for idle time, so take with salt
Yet, I'm typically at 2,200 with little idle so it's probably pretty close.

 

[ggrizzard]

If you have a Racor primary filter and can keep the bowl full while removing the tank you won't need to bleed the fuel line.

 

[dfischer]

Thanks for all the input. I have been able to confirm that the tank is completely full, so something went sorely amiss with my burn rate or I can lay claim to having the most miserly 2GM20f around. For safety's sake I'll assume something more like 1/2 gal/hr in the future.

 

[kjretlaw]

You can also get a yard stick one that 1/2" X 1/2" and dip the tank, Once you have a full mark the first 3" is about 5 Gal. I have one of the DNR fish measuring stickers on the outside of the tank so I can tell when I'm down 3" or about 5 Gal.

 

[Ralph Johnstone]

Does anyone have a quick procedure for determining the level of fuel in these tanks without spilling diesel into the bilge?

This can be used for dipping your tank although I installed it to test the fuel for sludge and water. Insert a small diameter wooden dowel to see the depth of the fuel.

 

[dfischer]

Actually, Ralph, your photo inadvertently hints at resolving another issue I've been having. I, too, have a diesel heater fuel supply fitting like yours; except the rubber seal is much thinner and allows diesel to weep out when the tank is full. Tightening the seal only distorts the plastic and makes it worse, but your robust rubber seal looks like just the ticket.

Thanks,
Doug

 

[Ralph Johnstone]

but your robust rubber seal looks like just the ticket.

I had exactly the same leakage problem last season when filling and the fuel gauge was a little off (whooooooole 'nother story). The excessive level was causing fuel to leak under the rubber gasket. Once the fuel level dropped, took the whole assembly apart, cleaned with rubbing alcohol and reassembled using Permatex #2 on the gasket faces. That's what you see oozing out from under the little SS plate. Permatex #2 is the only thing I've ever seen which actually sticks to polyethylene but does not dissolve in diesel.