Going on my first 4 day cruise on my H23.5 and I need to be able to motor 25 miles in the event of no wind. I have a 2stroke 8 hp Merc. Anyone know how many gallons of gas I should bring along if I plan to motor at 5 knots?? Thanks, Jack
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Oops! Too late!
I think you're kinda screwed... That's data you probably needed to collect on earlier experience with your specific engine. However, hopefully some folks here can give you some idea. Our engine is a 6hp & we didn't do enough motoring this season to really get a firm gauge. How large is your primary tank? If it's 5-6 gal, I'd guess you'd be OK, but that's easy for me to say. You may want to carry a second tank too, at least a smaller spare in case you need a gallon or two to get to the nearest gas dock. The question will be where to store it. If you have concerns about fuel economy, you may also think about revving at lower RPMs. I think the general rule is about 75% of full throttle is best. Much more, you're wasting fuel & running too hard if you're talking several hours under power; much less, the engine will begin forming deposits. I'd guess an 8hp would still be doing 5 kts at 75%. Sorry I can't help more. Hopefully you'll have fair winds! ------- Kevin s/v Grasshopper Hunter 23.5 Brownsville, VT
I think you're kinda screwed... That's data you probably needed to collect on earlier experience with your specific engine. However, hopefully some folks here can give you some idea. Our engine is a 6hp & we didn't do enough motoring this season to really get a firm gauge. How large is your primary tank? If it's 5-6 gal, I'd guess you'd be OK, but that's easy for me to say. You may want to carry a second tank too, at least a smaller spare in case you need a gallon or two to get to the nearest gas dock. The question will be where to store it. If you have concerns about fuel economy, you may also think about revving at lower RPMs. I think the general rule is about 75% of full throttle is best. Much more, you're wasting fuel & running too hard if you're talking several hours under power; much less, the engine will begin forming deposits. I'd guess an 8hp would still be doing 5 kts at 75%. Sorry I can't help more. Hopefully you'll have fair winds! ------- Kevin s/v Grasshopper Hunter 23.5 Brownsville, VT
You've GOT to get your mind RIGHT
To quote Strother Martin in "Cool Hand Luke". It is more helpful to think about motoring time ... rather than distance. Ask yourself, "How long will my motor run on a gallon of gas at about 80% throttle?". That way you can make adjustments on the spot for variables like going with or against the current, or the amount of wind resistance you are experiencing at the moment. Here's how the math might work. 5 gallon tank with 1 gallon an hour consumption yields 5 Knots for 5 hours will cover 21.75 statute miles But you might experience a contrary current that makes the math 1 gallon an hour at 4 Knots for 5 hours and cover only 17.4 statute miles OR the wind may be in your favor and you get 1/2 gallon an hour consumption for 5 Knots for 5 hours which will give you a cruising range of 43.5 statute miles It is NOT the same as highway miles. There are just too many real world variables. Even with the same model boat my mileage may be different because of propeller pitch ... or my motor may run leaner than yours ... or I may have more marine growth ... or my water and holding tanks may be full ... or I might be the one full of s**t, you never know. Ol' Dave
To quote Strother Martin in "Cool Hand Luke". It is more helpful to think about motoring time ... rather than distance. Ask yourself, "How long will my motor run on a gallon of gas at about 80% throttle?". That way you can make adjustments on the spot for variables like going with or against the current, or the amount of wind resistance you are experiencing at the moment. Here's how the math might work. 5 gallon tank with 1 gallon an hour consumption yields 5 Knots for 5 hours will cover 21.75 statute miles But you might experience a contrary current that makes the math 1 gallon an hour at 4 Knots for 5 hours and cover only 17.4 statute miles OR the wind may be in your favor and you get 1/2 gallon an hour consumption for 5 Knots for 5 hours which will give you a cruising range of 43.5 statute miles It is NOT the same as highway miles. There are just too many real world variables. Even with the same model boat my mileage may be different because of propeller pitch ... or my motor may run leaner than yours ... or I may have more marine growth ... or my water and holding tanks may be full ... or I might be the one full of s**t, you never know. Ol' Dave
Gas consumption info on Tohatsu site
Here is my experience for what it is worth. Your mileage will vary, as they say. There is no doubt that your boat, how much it is loaded, especially how fast you travel, and weather conditions will affect your milage as noted in the other posts. I also recommend you use time, not mileage. If you end up having to rely on a guess, and want a starting point, Tohatsu has some info about various of their outboards. It looks like their 8 hp 2 stroke running 5,000 rpm uses about 1.1 gallons an hour. If I were you, I would probably use 1.1 gallon per hour as a starting point if you are going where there could be strong currents or wave action. Here is another rule of thumb that I follow: bring enough fuel so that 1/3 gets you there, 1/3 gets you back and 1/3 is your reserve. I have used one gallon per hour for the MacGregor 26D with 8 hp Johnson Sailmaster 2 stroke for several years. We often cruised at half throttle, with some time at 3/4 throttle. We now have a Hunter 260 with a Tohatsu 9.9 four stroke. The heavier boat and more windage have offset the better gas mileage(adjusted for hp) of the four stroke, so guess what: we still use about one gallon per hour rule of thumb, but add about 10% for safety factor if we expect to cruise near the limit of 2/3 of our fuel. I would rather have it and not need it than need it and not have it
. Don't forget the 2 cycle oil you might need if you re-fill your tanks. I have found that it gets expensive at fuel docks. I see that you hail from Florida. We took our Hunter to Bimini this June and then down to the keys. I would go back right now if I could. You are lucky to be in Florida. Hope your trip goes well. PS. which outboard you use and its age plays a role. I think my Tohatsu is relatively low tech and may get worse mileage than more sophisticated makes. Still, I have owned two of the 9.9 Tohatsus and have had no problems at all.
Here is my experience for what it is worth. Your mileage will vary, as they say. There is no doubt that your boat, how much it is loaded, especially how fast you travel, and weather conditions will affect your milage as noted in the other posts. I also recommend you use time, not mileage. If you end up having to rely on a guess, and want a starting point, Tohatsu has some info about various of their outboards. It looks like their 8 hp 2 stroke running 5,000 rpm uses about 1.1 gallons an hour. If I were you, I would probably use 1.1 gallon per hour as a starting point if you are going where there could be strong currents or wave action. Here is another rule of thumb that I follow: bring enough fuel so that 1/3 gets you there, 1/3 gets you back and 1/3 is your reserve. I have used one gallon per hour for the MacGregor 26D with 8 hp Johnson Sailmaster 2 stroke for several years. We often cruised at half throttle, with some time at 3/4 throttle. We now have a Hunter 260 with a Tohatsu 9.9 four stroke. The heavier boat and more windage have offset the better gas mileage(adjusted for hp) of the four stroke, so guess what: we still use about one gallon per hour rule of thumb, but add about 10% for safety factor if we expect to cruise near the limit of 2/3 of our fuel. I would rather have it and not need it than need it and not have it
. Don't forget the 2 cycle oil you might need if you re-fill your tanks. I have found that it gets expensive at fuel docks. I see that you hail from Florida. We took our Hunter to Bimini this June and then down to the keys. I would go back right now if I could. You are lucky to be in Florida. Hope your trip goes well. PS. which outboard you use and its age plays a role. I think my Tohatsu is relatively low tech and may get worse mileage than more sophisticated makes. Still, I have owned two of the 9.9 Tohatsus and have had no problems at all.
Almost the Same Setup
I have a 23.5 with a 6HP Merc. I figure on 1 GPH as well. Attwood makes a six gallon tank that fits in the lockers I carry two. Makes it easy to mix the oil as a pint is exactly what you need for six gallons of fuel.
I have a 23.5 with a 6HP Merc. I figure on 1 GPH as well. Attwood makes a six gallon tank that fits in the lockers I carry two. Makes it easy to mix the oil as a pint is exactly what you need for six gallons of fuel.
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