I have recently purchased a CD33 with a Universal M-30 (24 horsepower, 3 cylinder diesel). I would like to determine the fuel consumption rate. Does a method / calculation exist? The cruising speed is listed as 2000 - 2400 RPM with a maximum RPM of 2800. I have just purchased the boat and would like to ascertain my motoring range before I begin the voyage to bring her home. My fuel capacity is 20 US gallons.
I would appreciate any advise or recommendations. I realize the range is determined by the sea conditions but a distance or hourly consumption estimate would be appreciated.
Motoring Range CD33?
Moderator: Jim Walsh
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Al Levesque
Re: Motoring Range CD33?
Congratulations on an excellent choice.Herb wrote: I have recently purchased a CD33 with a Universal M-30 (24 horsepower, 3 cylinder diesel).
... a distance or hourly consumption estimate would be appreciated.
The general feeling is that the engine uses one half gallon per hour. We tend to use 0.6 gallons per hour. We usually cruise at about 1900 RPM. That seems to be where the boat speed is about 5.5 knots and the engine stays at about 170-180F. I guess that means we could run 30 hours and cover about 150 miles. Since we usually sail some of the way and carry a six gallon jug and refill during the day, we have never tested the limit.
Hope this helps and that you enjoy the trip home.
Al
CD33, Athena
levesquealbert@netscape.net
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Ryan Turner
Re: Motoring Range CD33?
You're gonna love that CD33! I've tested my fuel consumption rate and found it to be about 0.4 gph. That gives me about 50 hours of motoring. I usually run around 1,900 rpm or whatever keeps the engine temp around 170 to 185. Make sure your tank is full when you leave and you should get the 50 hours of motoring before you've got to fill up again.
Ryan Turner
s/v Zenobia
CD33 hull no. 100
rdtec@aol.com
Ryan Turner
s/v Zenobia
CD33 hull no. 100
Herb wrote: I have recently purchased a CD33 with a Universal M-30 (24 horsepower, 3 cylinder diesel). I would like to determine the fuel consumption rate. Does a method / calculation exist? The cruising speed is listed as 2000 - 2400 RPM with a maximum RPM of 2800. I have just purchased the boat and would like to ascertain my motoring range before I begin the voyage to bring her home. My fuel capacity is 20 US gallons.
I would appreciate any advise or recommendations. I realize the range is determined by the sea conditions but a distance or hourly consumption estimate would be appreciated.
rdtec@aol.com
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Matt Cawthorne
Fuel burn is very speed dependant
Herb,
Nice boat. My boat is a 36 so the fuel burn rate is not the same, but the following applies to all displacement hulls. Fuel consumption is not linear with speed. If my memory is correct when you begin to get near hull speed the consumption is proportional to speed cubed. If my memory is correct about it being a cubic curve then dropping from 5 knots to 4 would cut the consumption nearly in half and extend the range by 56%. The savings are not worth the time when you are near fuel supplies, but if you happen to take a long trip where fuel will not be available or happen to be running low then it is worth slowing down. One should not carry this too far because engine efficiency drops when you slow too much and if you slow down too much you will eventually get carbon deposits in the engine. Of course when the waves are up you will burn lots of extra fuel, but when the waves are up the wind is usually up as well and the motor is not usually needed.
The Perkins 4.108 engine in my '36 is rated at 50 hp, but when I run it at a speed which makes the boat go at just below 5 knots my fuel consumption for the year averages about .36 gph. When I get closer to 6.5 knots the consumption is more than double, but I don't run it that hard very often so I do not have an accurate number.
Good luck and enjoy your boat.
Matt
mcawthor@bellatlantic.net
Nice boat. My boat is a 36 so the fuel burn rate is not the same, but the following applies to all displacement hulls. Fuel consumption is not linear with speed. If my memory is correct when you begin to get near hull speed the consumption is proportional to speed cubed. If my memory is correct about it being a cubic curve then dropping from 5 knots to 4 would cut the consumption nearly in half and extend the range by 56%. The savings are not worth the time when you are near fuel supplies, but if you happen to take a long trip where fuel will not be available or happen to be running low then it is worth slowing down. One should not carry this too far because engine efficiency drops when you slow too much and if you slow down too much you will eventually get carbon deposits in the engine. Of course when the waves are up you will burn lots of extra fuel, but when the waves are up the wind is usually up as well and the motor is not usually needed.
The Perkins 4.108 engine in my '36 is rated at 50 hp, but when I run it at a speed which makes the boat go at just below 5 knots my fuel consumption for the year averages about .36 gph. When I get closer to 6.5 knots the consumption is more than double, but I don't run it that hard very often so I do not have an accurate number.
Good luck and enjoy your boat.
Matt
Herb wrote: I have recently purchased a CD33 with a Universal M-30 (24 horsepower, 3 cylinder diesel). I would like to determine the fuel consumption rate. Does a method / calculation exist? The cruising speed is listed as 2000 - 2400 RPM with a maximum RPM of 2800. I have just purchased the boat and would like to ascertain my motoring range before I begin the voyage to bring her home. My fuel capacity is 20 US gallons.
I would appreciate any advise or recommendations. I realize the range is determined by the sea conditions but a distance or hourly consumption estimate would be appreciated.
mcawthor@bellatlantic.net
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Neil Gordon
Re: Motoring Range CD33?
>>That gives me about 50 hours of motoring.<<
Just remember that if the fuel is old and the boat is old, there will be lots of crud in the tank. The closer you get to the bottom, the more likely the accumulated gunk will have clogged the filters.
I'd keep a big reserve just in case... probably not take a trip where the tank would likely fall below half way.
Regards, Neil
s/v LIQUIDITY
Cape Dory 28 #167
neil@nrgordon.com
Just remember that if the fuel is old and the boat is old, there will be lots of crud in the tank. The closer you get to the bottom, the more likely the accumulated gunk will have clogged the filters.
I'd keep a big reserve just in case... probably not take a trip where the tank would likely fall below half way.
Regards, Neil
s/v LIQUIDITY
Cape Dory 28 #167
neil@nrgordon.com
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Ryan Turner
Cruddy Fuel
Good point. So how does one clean out an old tank with years of crud in it? Surely there must be a way. This seems like a prudent thing to do when you own an old boat.Neil Gordon wrote: Just remember that if the fuel is old and the boat is old, there will be lots of crud in the tank. The closer you get to the bottom, the more likely the accumulated gunk will have clogged the filters.
Ryan Turner
s/v Zenobia
CD33 hull no. 100
rdtec@aol.com
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Neil Gordon
Re: Cruddy Fuel
>>So how does one clean out an old tank with years of crud in it?<<
You can clean the fuel by draining the tank and filtering. Tanks can be cleaned, too, but it's hard if there's no access port.
I just suggest being prudent and not relying on what's near the bottom of the tank. Also remember that you can usually sail out of trouble better than you can motor from it.
Regards, Neil
s/v LIQUIDITY
Cape Dory 28 #167
neil@nrgordon.com
You can clean the fuel by draining the tank and filtering. Tanks can be cleaned, too, but it's hard if there's no access port.
I just suggest being prudent and not relying on what's near the bottom of the tank. Also remember that you can usually sail out of trouble better than you can motor from it.
Regards, Neil
s/v LIQUIDITY
Cape Dory 28 #167
neil@nrgordon.com