10 HP Four-Stroke Fuel Consumption

[Doug Lord]

This is very preliminary for me. Does anybody have any fuel consumption info. on a 4-stroke 10hp outboard pushing a very light boat about three-quarter throttle? Or any fuel consumption data for a 10hp four stroke in any application? Thanks!

[masalai]

If you are looking for best mileage, sadly the make I cannot remember (not made any more that I can find) had a Hi-thrust big diameter propeller and low gearing so a bigger pitch could be applied - excellent for propelling sailing boats... It would be a good idea to recondition a second hand one and they came as 4 stroke outboards... When I was evaluating the 39C it was powered by twin 10hp 4 stroke outboards to good effect... Was it a "mariner 10 high thrust"?

Anyhow, that is what you should consider for auxiliary power for your sailboat, if you can find one... The key being a slow rotating propeller giving a high torque output for maximum range for a given amount of fuel... Torqeedo R4 electric outboards were my next selection and supplemented with solar panels and a genset for cloudy days / extra power, but getting a genset and matching power needs became an issue... Eventually I went to Kubota/nanni because I know and have confidence in the engine... and can get parts throughout the western Pacific / Asia region...

[Doug Lord]

Thanks, Masalai. This would be for an 16-20' lightweight power tri or cat-as I said very preliminary. Just trying to get a feel for an outboards' fuel consumption. I hate gasoline but for this I'll probably use it. I've cruised a lot in the past-my parents dragged me along on a motorsailer from 0-5 all over the US east coast, Cuba, Nova Scotia, the Islands and Brazil. My memory of that time is ,shall we say, a bit faded. They tell me I had a girlfriend on the Isle of Pines and sometimes I actually think I remember her!
Lived on a boat ,mostly, from then to about age 18 and on the coast now.
I want to"gunkhole" the hell out of Florida-I love this place and it's intricate waterways.

[Boston]

go diesel and your millage improves dramatically
go bio-diesel and your costs plummet
after that its looking for small gains other than by following the performance curve of your hull, which half the folks in here could show you if you provide the exact hull design

you might pay a bit more for a diesel up front but the potential savings way outweigh the costs

[masalai]

For a live-aboard gunk-holer, I would think in terms of something about 30ft loa

http://www.thecoastalpassage.com/cheapcat.html is easy to build and easy to push with any small outboard (electric torqeedo R4000 or 10 hp petrol outboard in a pod slung aft centreline... Get the boat sorted and built asap...

[Submarine Tom]

Originally Posted by Doug Lord

This is very preliminary for me. Does anybody have any fuel consumption info. on a 4-stroke 10hp outboard pushing a very light boat about three-quarter throttle? Or any fuel consumption data for a 10hp four stroke in any application? Thanks!

About 1/2 gallon per hour as I recall.

-Tom

[Boston]

I don't think your going to be living aboard that thing very comfortably, no head room. But it is cheap and it is fuel efficient, except maybe for the rigging which depending on location is a kinda expensive option, free bio-diesel and a diesel engine are bound to work out cheaper than rigging.

[Doug Lord]

Originally Posted by masalai

For a live-aboard gunk-holer, I would think in terms of something about 30ft loa

http://www.thecoastalpassage.com/cheapcat.html is easy to build and easy to push with any small outboard (electric torqeedo R4000 or 10 hp petrol outboard in a pod slung aft centreline... Get the boat sorted and built asap...

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Masalai, at this point thats too big. I want to trailer to a location and spend no more than a couple of weeks-if that-aboard. And because I'm bullheaded I want to design the thing(with help from a na/marine engineer friend).....But it is probably years off.

[Doug Lord]

Originally Posted by Submarine Tom

About 1/2 gallon per hour as I recall.

-Tom

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Thanks very much, Tom. That is excellent!

[Doug Lord]

Originally Posted by Boston

I don't think your going to be living aboard that thing very comfortably, no head room. But it is cheap and it is fuel efficient, except maybe for the rigging which depending on location is a kinda expensive option, free bio-diesel and a diesel engine are bound to work out cheaper than rigging.

==================
Thanks, Boston. It's not a sailboat-small power cat or tri(with a "get home" rig maybe). I'd like to use a diesel depending on cost and weight-I'll look into it as time goes by.

[DCockey]

Published data from several outboard manufactuers runs about 0.1 gal/hr per HP for 4-stroke outboards at full throttle. Close the throttle some and fuel consumption falls.

[DCockey]

Originally Posted by Boston

go diesel and your millage improves dramatically
go bio-diesel and your costs plummet
after that its looking for small gains other than by following the performance curve of your hull, which half the folks in here could show you if you provide the exact hull design

you might pay a bit more for a diesel up front but the potential savings way outweigh the costs

Total cost of the Diesel vs the outboard depends on how much the engine is used, and the cost of fuel. Assuming a 10 HP outboard costs $2000 and a 10HP Diesel installed costs $6000 the difference is $4000. If fuel for both costs $6/gal then 667 gallons of fuel would need to be saved. If the outboard is run at full throttle and consumes 1 gal/hour, and the Diesel consumes half as much (probably to little fuel for the Diesel) then engine would need to be used for 1333 hours before the Diesel broke even. And that's not counting the time-cost of money.

From the little I've seen bio-diesel generally is more expensive to buy than regular diesel.

[Doug Lord]

Originally Posted by DCockey

Published data from several outboard manufactuers runs about 0.1 gal/hr per HP for 4-stroke outboards at full throttle. Close the throttle some and fuel consumption falls.

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Thanks very much!

[Boston]

Originally Posted by DCockey

Total cost of the Diesel vs the outboard depends on how much the engine is used, and the cost of fuel. Assuming a 10 HP outboard costs $2000 and a 10HP Diesel installed costs $6000 the difference is $4000. If fuel for both costs $6/gal then 667 gallons of fuel would need to be saved. If the outboard is run at full throttle and consumes 1 gal/hour, and the Diesel consumes half as much (probably to little fuel for the Diesel) then engine would need to be used for 1333 hours before the Diesel broke even. And that's not counting the time-cost of money.

From the little I've seen bio-diesel generally is more expensive to buy than regular diesel.

Assuming you are paying for bio-diesel, the stuff is easily made from vegi oil, or you can just run the vegi oil straight with minor modifications in the right kind of engine, IDI naturaly aspirated, mechanical pump. I have numerous sources of free oil both WMO and WVO and I presently save about $120 to $150 a week in fuel expenses. I've got a 200 gallon tank in the back of my truck and I could easily provide my own fuel rather than pay the exorbitant dock rates. Thing is folks make it sound a lot harder than it is. With the right engine its a simple mater of picking up WVO and letting it settle for a few weeks, then draining out the solids and run the remaining fluid through a simple filter, into the tank it goes. Works great at temps above about 50°F, bellow that you have to modify a few things but it still works fine. If you decide to go bio-diesel then its just like diesel and there are no modifications needed for low temp environments. Saves me a fortune and I got the truck free as well.

[Submarine Tom]

Originally Posted by DCockey

Published data from several outboard manufactuers runs about 0.1 gal/hr per HP for 4-stroke outboards at full throttle. Close the throttle some and fuel consumption falls.

That would make it ~3/4 of a gallon per hour then.

I'm going to revise my estimate to 2/3 gph then for a 10 Hp 4-stroke at 3/4 throttle.

Personaly, I'd run her wide open as you'll probably get better economy from the added speed you'd attain. Oh, maybe not because you're talking about two engines now aren't you...

-Tom