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  #1  
Old 07-10-2012
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Diesel consumption.

My New-To-Me Hunter 30' had a fuel gauge.

The fuel gauge was located on top of the fuel tank.

The fuel tank is conveniently located under the cockpit, between two lockers.

To read (or rather: "attempt to read") the gauge one had to empty a locker, invert one's self (with someone holding one's ankles). In this way one could see the gauge, but not read the fuel level on it.

I spoke to a bunch of people about fuel consumption and most of the responses involved keeping track of hours run (and RPM's) and diesel added. In that way the consumption rate could be established.

Well, Dammit Jim! I'm a cook not a mathematician (or 'electrician' - more on that later).

I decided to install a new gauge attached to a sending unit.

I replaced the old gauge and float with a new float and sending unit and wired it all to a switch and shiny gauge that I inserted into my cockpit coaming.

The damned thing didn't work.

I didn't have time to play around with it as I was heading out for a week and a half with my wife. I was convinced that I was running low on diesel at one point so I reverted to the tried and true technique of inserting a wooden spoon handle into the tank. Worked a treat!

A good friend of mine is an electrical engineer. I asked him to take a look at the new gauge's wiring , determine why it wasn't working.

He was very impressed by my work and said that the installation was perfect except for three 'minor' mistakes.
  1. The connections were not secure - who knew that ring connectors are rated by wire gauge as well as the size of the hole?
  2. The wires were connected to the wrong terminals.
  3. And the polarity was backwards.

Other than that he said I did an expert job.

The gauge seems to be working now.

While the gauge was not working I decided to track the engine hours and try to ascertain fuel consumption rates.

I came up with this engine log. Please let me know if you think it would be useful and if you believe it should have more information.

Thanks.

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Old 07-10-2012
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Re: Diesel consumption.

I think you want to add RPMs. If I run at 1800 RPM's (my sweet spot) I get @80% power (approx 5kn) and 2hrs/gal. If I run all out at 2800 RPMs I get 100% power (6kn+) but as little as 3/4hr/gal. You want to track your consumption levels. To do that, you'll need to keep an eye on your engine speed.
.02
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Old 07-10-2012
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Re: Diesel consumption.

Quote:
Originally Posted by blowinstink View Post
I think you want to add RPMs. If I run at 1800 RPM's (my sweet spot) I get @80% power (approx 5kn) and 2hrs/gal. If I run all out at 2800 RPMs I get 100% power (6kn+) but as little as 3/4hr/gal. You want to track your consumption levels. To do that, you'll need to keep an eye on your engine speed.
.02
Matt
I guestimated about 2 litres per hour at 2000 RPM - that's about 1 gal(US) per two hours - pretty close.

What size engine do you have and what size boat? do you tow a dinghy?

I have a 30' Hunter (9500#'s approx.) and I used to tow a heavy dink. I just picked up a very light RIB (60 #'s) so mileage will go up. I have a 18 horse Yanmar diesel.
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Old 07-10-2012
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Re: Diesel consumption.

What size and make of engine do you have?
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Old 07-10-2012
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Re: Diesel consumption.

Quote:
Originally Posted by sebez View Post
What size and make of engine do you have?
Yanmar 2GM20
Quote:
Originally Posted by flyingwelshman View Post
I have an 18 horse Yanmar diesel.
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Re: Diesel consumption.

I still use the stick.
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Old 07-10-2012
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Re: Diesel consumption.

My 2 engines are single cylinder Yanmar 1GM10s. I use 1 pint of fuel per hour per engine at 2500 RPM. These are in a catamaran, obviously with no lead ballast. Mileage is pretty darn good!!
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Old 07-10-2012
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Re: Diesel consumption.

Quote:
Originally Posted by flyingwelshman View Post
My New-To-Me Hunter 30' had a fuel gauge.

The fuel gauge was located on top of the fuel tank.

The fuel tank is conveniently located under the cockpit, between two lockers.

To read (or rather: "attempt to read") the gauge one had to empty a locker, invert one's self (with someone holding one's ankles). In this way one could see the gauge, but not read the fuel level on it.

I spoke to a bunch of people about fuel consumption and most of the responses involved keeping track of hours run (and RPM's) and diesel added. In that way the consumption rate could be established.

Well, Dammit Jim! I'm a cook not a mathematician (or 'electrician' - more on that later).

I decided to install a new gauge attached to a sending unit.

I replaced the old gauge and float with a new float and sending unit and wired it all to a switch and shiny gauge that I inserted into my cockpit coaming.

The damned thing didn't work.

I didn't have time to play around with it as I was heading out for a week and a half with my wife. I was convinced that I was running low on diesel at one point so I reverted to the tried and true technique of inserting a wooden spoon handle into the tank. Worked a treat!

A good friend of mine is an electrical engineer. I asked him to take a look at the new gauge's wiring , determine why it wasn't working.

He was very impressed by my work and said that the installation was perfect except for three 'minor' mistakes.
  1. The connections were not secure - who knew that ring connectors are rated by wire gauge as well as the size of the hole?
  2. The wires were connected to the wrong terminals.
  3. And the polarity was backwards.

Other than that he said I did an expert job.

The gauge seems to be working now.

While the gauge was not working I decided to track the engine hours and try to ascertain fuel consumption rates.

I came up with this engine log. Please let me know if you think it would be useful and if you believe it should have more information.

Thanks.

Looks fine, except there's nowhere to record how many gallons you're using. Geez what's the use of it without that!


I think you could also just go by the old rule of 18HP/Gal/HR. Look at your engine manual and see how many HP you're using at your chosen RPM (assuming correctly sized prop) and you'll be really close.

See also this thread:
fuel consumption gas vs diesel

MedSailor
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Old 07-10-2012
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Re: Diesel consumption.

Hey,

My boat has a functioning fuel gauge. I also have a functioning hour meter. From 6 years of use I know that I use, on average, about 1/2 gallon an hour. This is for a Universal M25 turning a 3 blade prop, and the boat is an O'day 35. I typically run the engine at 80% of max rpm. On my boat that means I move at about 6 kts.

Considering that I use my engine about 50 hours a year I start the season with a fuel tank, fill it again in August, and then at the end of the season.

Real simple.

Barry
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Old 07-11-2012
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Re: Diesel consumption.

Quote:
Originally Posted by flyingwelshman View Post
Quote:
i guestimated about 2 litres per hour at 2000 rpm - that's about 1 gal(us) per two hours - pretty close.
by adding rpm to your sheet, you won't be "guestimating" - you'll know what your consumption is at various power points.

Quote:
what size engine do you have and what size boat? Do you tow a dinghy?
25hp. 33' boat is about 7-8ton all up. Tow dink sometimes.

My point was / is that by tracking the actual consumption you will get to know what *your boat* consumes.
-m
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