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With gas prices reaching unprecedented levels, our webmaster (Bill) has been grousing at me for several weeks to consider a tech note with suggestions aimed at cutting down on fuel consumption. I've been somewhat slow to pick up the torch, believing that the price of gasoline has little impact on a group of sailors who historically worry mostly about using their fuel so slowly that they fear it might go stale.
However, Bill finally came up with three sets of numbers that are difficult to ignore:
* An Atomic 4 in reasonably good condition can conservatively cruise at 5.5 knots, burning 1.0 gallons per hour.
* If you can cut your fuel consumption to 0.75 gallons per hour (quite easy to do with an adjustable main jet), you can motor for 1.33 hours for each gallon of fuel, which represents an increase in cruising range of 33%.
* If/when the price of gas in your neighborhood reaches $3.75 per gallon; decreasing fuel consumption from 1.0 gallons per hour to 0.75 gallons per hour could save you approximately $50 during an average season (50 hours of engine operation).
Even if you remain indifferent to the rising fuel costs, a 33% increase in cruising range translates into quite a few less stops at fuel docks, so here are some things that you can do to improve your fuel economy that are quite easy and which create little or no expense:
1) Recheck your ignition timing by performing a simple timing advance check under power. This check is performed by loosening the distributor hold-down bracket and rotating the distributor a slight amount in each direction until you find the spot of highest RPM. Retighten the distributor in this new location of highest RPM. Operating on either side of this optimum advance setting will have a detrimental effect on fuel economy.
2) Fuel economy can also be greatly enhanced by staying a bit further away from your theoretical hull speed when setting your cruising speed (getting there is supposed to be half the fun anyway). The power required to move a sailboat to a hull speed of 6.5 knots goes up disproportionately to that required to move the same boat at 5.5 knots. In other words, you don't make up the difference in fuel consumption by getting to your destination that much faster.
3) Fine-tune your fuel mixture with an adjustable main jet. Our intracoastal cruising customers report that they're usually able to easily achieve the reductions in Bill's above example with the installation of an adjustable main jet alone. Click here to view this product:
Here are the installation steps to help you decide if it's something that you would like to consider:
INSTALLING AN ADJUSTABLE MAIN JET:
a. Remove the fixed main jet from your carburetor, and install the fixed part of the adjustable assembly. The fixed jet of the adjustable assembly looks much like the original jet, except that the orifice in the adjustable one is larger.
CAUTION: Both the fixed jet and the 1/2" hex-headed plug of the needle assembly have hard washers to seal them after installation. Use care in removing the original fixed jet so as to not lose the original washer. If the original washer remains in the carburetor instead of coming out with the jet, it's usually preferable to leave it in place and save the new washer for a spare. Do not end up using both small washers behind the fixed jet. Also, do not overtighten the 1/2" hex head of the needle assembly, or the sealing washer is likely to extrude out from under the hex head and cause a leak.
b. After the fixed jet is in place, thread the adjustable needle assembly into the main passage, in place of the main passage plug. Make sure that the adjustable needle of the valve is backed out far enough so as not to seat against the fixed jet.
c. After the needle assembly is installed and tightened, turn the "T" handle on the end of the needle in until you feel it make contact with the fixed jet. Then back the needle out approximately 1 and 1/2 turns. This should be a good initial setting. After warming up the engine, and at your favorite cruising power setting, turn the "T" handle in and out until you find the best RPM.
NOTE: You will find quite a large zone in the adjustment process where the engine performance will not noticeably change as the "T" handle is turned one way or the other. By turning the "T" handle in (clockwise) until a definite decrease in engine performance is noted, and then backing it out just until power is restored, the best fuel economy will be achieved.
d. After the installation is complete, it may be necessary to tighten the 5/16" packing gland nut to seal around the shaft of the needle. Tightening this packing gland after the final adjustment is made will also insure that the adjustment will not slip over time.
Don
However, Bill finally came up with three sets of numbers that are difficult to ignore:
* An Atomic 4 in reasonably good condition can conservatively cruise at 5.5 knots, burning 1.0 gallons per hour.
* If you can cut your fuel consumption to 0.75 gallons per hour (quite easy to do with an adjustable main jet), you can motor for 1.33 hours for each gallon of fuel, which represents an increase in cruising range of 33%.
* If/when the price of gas in your neighborhood reaches $3.75 per gallon; decreasing fuel consumption from 1.0 gallons per hour to 0.75 gallons per hour could save you approximately $50 during an average season (50 hours of engine operation).
Even if you remain indifferent to the rising fuel costs, a 33% increase in cruising range translates into quite a few less stops at fuel docks, so here are some things that you can do to improve your fuel economy that are quite easy and which create little or no expense:
1) Recheck your ignition timing by performing a simple timing advance check under power. This check is performed by loosening the distributor hold-down bracket and rotating the distributor a slight amount in each direction until you find the spot of highest RPM. Retighten the distributor in this new location of highest RPM. Operating on either side of this optimum advance setting will have a detrimental effect on fuel economy.
2) Fuel economy can also be greatly enhanced by staying a bit further away from your theoretical hull speed when setting your cruising speed (getting there is supposed to be half the fun anyway). The power required to move a sailboat to a hull speed of 6.5 knots goes up disproportionately to that required to move the same boat at 5.5 knots. In other words, you don't make up the difference in fuel consumption by getting to your destination that much faster.
3) Fine-tune your fuel mixture with an adjustable main jet. Our intracoastal cruising customers report that they're usually able to easily achieve the reductions in Bill's above example with the installation of an adjustable main jet alone. Click here to view this product:
Here are the installation steps to help you decide if it's something that you would like to consider:
INSTALLING AN ADJUSTABLE MAIN JET:
a. Remove the fixed main jet from your carburetor, and install the fixed part of the adjustable assembly. The fixed jet of the adjustable assembly looks much like the original jet, except that the orifice in the adjustable one is larger.
CAUTION: Both the fixed jet and the 1/2" hex-headed plug of the needle assembly have hard washers to seal them after installation. Use care in removing the original fixed jet so as to not lose the original washer. If the original washer remains in the carburetor instead of coming out with the jet, it's usually preferable to leave it in place and save the new washer for a spare. Do not end up using both small washers behind the fixed jet. Also, do not overtighten the 1/2" hex head of the needle assembly, or the sealing washer is likely to extrude out from under the hex head and cause a leak.
b. After the fixed jet is in place, thread the adjustable needle assembly into the main passage, in place of the main passage plug. Make sure that the adjustable needle of the valve is backed out far enough so as not to seat against the fixed jet.
c. After the needle assembly is installed and tightened, turn the "T" handle on the end of the needle in until you feel it make contact with the fixed jet. Then back the needle out approximately 1 and 1/2 turns. This should be a good initial setting. After warming up the engine, and at your favorite cruising power setting, turn the "T" handle in and out until you find the best RPM.
NOTE: You will find quite a large zone in the adjustment process where the engine performance will not noticeably change as the "T" handle is turned one way or the other. By turning the "T" handle in (clockwise) until a definite decrease in engine performance is noted, and then backing it out just until power is restored, the best fuel economy will be achieved.
d. After the installation is complete, it may be necessary to tighten the 5/16" packing gland nut to seal around the shaft of the needle. Tightening this packing gland after the final adjustment is made will also insure that the adjustment will not slip over time.
Don
Attached Files
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an hour, this is over about 80 hours of motoring. My cruise setting is 2,000 RPM's (Indigo prop) at 8.5 inches of vacuum. If I run harder say 2200 I use a bit over a gallon an hour and far less below 1900. My engine is tired and has two cylinders with low compression, I use a quart of oil in about 50 hours. I am using a fixed jet however I have done a lot of tinkering with the carb!
. I have adjusted to many A-4's over the years that have the idle set way to rich
, it does help the engine "start" a bit faster but then it just fouls or soots up the plugs if you need to idle or run at slow speeds.
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