How many gallons/per hour does a 9.9 hp RIB burn

[Bene505]

Actually, how many miles per gallon do you get from a 9.9 horsepower inflatable? Assume you are up on plane.

This would be useful to know if, for instance, you were taking your RIB from one island to the next to get groceries or whatever.

[mrwuffles]

I cannot imagine anything more that 2 gal and hour and that is probably with a strong headwind and seas, this is what google came up with, Outboard Fuel Consumption - World Cruising and Sailing Forums

[pdqaltair]

Originally Posted by mrwuffles

I cannot imagine anything more that 2 gal and hour and that is probably with a strong headwind and seas, this is what google came up with, Outboard Fuel Consumption - World Cruising and Sailing Forums

But milage in a displacement hull is very speed sensitive, and on a planing boat it is going to be very weight sensitive. For example, my little 4hp will plane my sport boat and me at a very respectable pace, but when a second person is added - displacement mode and less than 1/3 the speed. Your boat loaded with provisions and 2 people may not plane with 9.9HP, and if it does, it will take all of it.

The consumption figure of 0.1 gph per HP is, of course, wide open.

Load her up and find out!

[Bene505]

Originally Posted by pdqaltair

... The consumption figure of 0.1 gph per HP is, of course, wide open.

Where's that from. That sounds way too low.

[Bene505]

Another reason to ask this question. If you hit a shipping container, how far could your dinghy carry you, with X gallons of gas?

[mrwuffles]

That is exactly what the link said I posted but who knows if that is right, 10% and .1 per HP are the same thing.

[Bene505]

Sorry guys, I misread it. 0.1gph PER HORSEPOWER. That seems right.

So If I'm up on plane and using 8 hp of my engine's capability, and I'm doing 20 knots with 5 gallons of gas.... I can go 5*20/0.8 = 125 nm on a tank. That's really something.

I wonder what ocean conditions will allow a dinghy to go up on plane.

[pdqaltair]

Originally Posted by Bene505

Where's that from. That sounds way too low.

But I do think it is close. I know my 18 hp would burn just less than 2 per hour and my 9.9 hps burn about 1 per hour.

By the way, the 18 hp was on a Stiletto cat. At 18 hp I got 11 knots and ~ 5.7 mpg. At ~7 hp I got 6.5 knots and 8.0 mpg. That is not a displacement hull, either.

[brak]

My 4 hp dinghy motor burns about 1/4 gallon of gas per hour. Consumption goes up if I take it on a plane (though I rarely do, it's not that much fun), may be double that.

[Bene505]

Thanks for the posts. I'm wondering now if anyone has used their dinghy as a lifeboat and has any experience with this.