21' Glasply/165 IL6 fuel consumption??

[DonRutledge]

I am currently rebuilding a 1972, 21' Glassply cuddy with a Mercruiser 165 IL6 sterndrive. I have the floor, stringers and transom ripped out and ready for replacment. <br /><br />The original design had a 60 gallon fuel tank in the center, under the floor. I would like to convert that area into a fishbox. I plan on using this boat to fish for albacore off the Oregon coast, so my fuel capacity needs to allow me to travel as much as much as 150 miles in a day not including a 30% safety factor. <br /><br />I plan on adding new plastic fuel tanks under the seat boxes. I need to figure out a way to size the new tanks. I know there are too many variables to come up with an accurate figure. The only real way to know this number will be to make some test runs and figure out my milage. But, I really would like to have a ballpark idea as to what to expect. Does anybody have any real world data on this hull/motor (or similar) combination?

 

[levittownnick]

Re: 21' Glasply/165 IL6 fuel consumption??

An old estimate for fuel consumption is 1 gallon per hour for each 10 horse power. Therefore if you divide your engine's hp by 10 it will give your gallons per hour. If you know how many hours the trip will take - you have it made.

 

[cuzner]

Re: 21' Glasply/165 IL6 fuel consumption??

Fuel consumption is based more on the way you drive your boat than the engine. You have to find your sweet spot and cruise there.<br /><br /> Jim

 

[mikeh61]

Re: 21' Glasply/165 IL6 fuel consumption??

I once owned a 23' center console equipped with that engine and outdrive. It would cruise at 24mph and yield 3.96mpg on a calm ocean for a consumption rate of 6gph approx. I don't recall the weight of that boat, but it's probably comparable to yours. When heavily loaded, or on rough water, it wouldn't do as well. Hope this helps. MIKE

 

[glasply79]

Re: 21' Glasply/165 IL6 fuel consumption??

Aloha,<br /> I have a 24' Glasply and was burning about 2.5 GPH...have a diesel though. My boat is under construction...decided to do a complete overhaul, paint wiring outdrive, etc. Im not touching the engin internals, only rebuilding externals as needed. Transom may need to be ripped out in the future. Do you have any pics of your rebuild? I am very interested in seeing the hull construction if I need to redo transom. I may put together a website this week documenting my rebuild.<br />Aloha,<br />Mike