Small boat MPG?

[ZmOz]

I'm thinking about getting a 12-14 foot aluminum boat with around a 10hp outboard for when I don't want to mess with or feed my ski boat. What kind of MPG could I expect from a boat like that? My 16 footer only gets around 2mpg. :'( I know that's kind of vague but I don't have anything in particular picked out yet....

Also, what kind of range would I have with a trolling motor and an average group 24 battery?

 

[cobra 3.0]

Re: Small boat MPG?

You can fish almost 2 full days with a 5 gallon tank. If you go four stroke, the economies are even better if you troll a lot. Personally I'd buy a 15hp if it's in the same size instead of a 10.

For an electric trolling motor, it really depends how fast and how big the trolling motor is. With a 28 lb thrust I average between 2 hours to any where up to 5 hours.

 

[Silvertip]

Re: Small boat MPG?

A trolling motor with pulse technology (Maximizer is MinnKota technology) provides run times considerably longer when running at slower speeds. At full speed, it doesn't matter what technology you have. A 10 HP engine will burn roughly 1 gallon of fuel per hour at wide open throttle. Boat type, load, throttle setting and water conditions will dictate what what any throttle setting translates to in miles per gallon.

 

[tashasdaddy]

Re: Small boat MPG?

unless you are fishing hp restricted lakes, i say 14' with 15 hp. and rig it with ez guide stick steering and remote controls to the front seat. this way you can distribute the load in the boat correctly . gas in stearn, batteries mid section, you and troller in bow, i'm sorry i ever sold this boat, controls center seat, (rope start) would run 20-25 mph, love rough water, never burnt more than 3 gallons a day. '55 15 hp rude, '60 14' lonestar.

http://i46.photobucket.com/albums/f119/tashasdaddy/MVC-905S-1.jpg

 

[bassboy1]

Re: Small boat MPG?

We've run our 12 foot Vee with 4 horse 'rude about ten miles since we've owned it. Used between 3/4 and 1 gallon. Running it as WOT most of the time, and since it won't plane, it is just plowing.

 

[steelespike]

Re: Small boat MPG?

A 10 hp uses about 1 GPH and under good conditions
can do about 20 mph.Pretty easy equation 20MPG.
Probably end up a little less but it sounds good to me.

 

[ZmOz]

Re: Small boat MPG?

Would a 20hp be too much for a 14' boat? 8) I'm thinking mostly about something I could use to drive into Portland...about 20 miles down river. I thought there was a HP restriction at a near by place, but there isn't...

 

[River - Runner]

Re: Small boat MPG?

Now it depends on how fast you want to go.

My 14 ft., 207 lb. FD Alumacraft

4 hp.

25 hp.

40 hp.

 

[scoutabout]

Re: Small boat MPG?

Would a 20hp be too much for a 14' boat? ...

It really depends on overall boat design, length being just one factor. I've got a 14 foot Springbok with a 7.5 hp that I would say is ever so slightly underpowered. The max rating of 15hp would really be great in terms of speed but I'd be concerned considering how little freeboard it has combined with not much beam. I've seen aluminum boats of the same length, however, that look perfectly happy with 40hp -- they are much wider and deeper, though.

 

[steelespike]

Re: Small boat MPG?

I've seen 14s rated for 15 to 40 hp.There should be a plate on the transom.If not take the demensions and compare to new boats on the net.
I would go with the most you can afford and is safe.
Keep in mind a 20 will use about twice the gas at wot while only making about 25% more speed.Although if you go 3/4 or so throttle you could save gas and may still out do the 10 for speed.And of course the 20 will plane a load better which might save some gas over distance.
Another consideration is boat size.Generally speaking a big bare bones utility will plane a load better than a smaller boat.My 15 ft with a 25 wouldn't plane with 5 adults but my 18 ft planed easily with the same motor.
And felt like a you were much safer.I think it is safe to say the bigger boat will stay on plane easier at reduced power as well.

 

[waterinthefuel]

Re: Small boat MPG?

Would a 20hp be too much for a 14' boat? 8) I'm thinking mostly about something I could use to drive into Portland...about 20 miles down river. I thought there was a HP restriction at a near by place, but there isn't...

I have a 13.5 foot boat with a 28 Evinrude, and that little boat is a screamer. I can keep up with 40's and some 50's.

 

[ZmOz]

Re: Small boat MPG?

So how would the gas mileage of a 20hp at ~3/4 throttle compare to the mileage of a 15hp at full throttle on the same boat? I'm thinking the 20hp would be more efficient since it's not working as hard. I just measured the route I want to take in google earth and it's more like 38 miles one way. :^

 

[baconbiscut]

Re: Small boat MPG?

With my 5.5 I can go about 17 miles at wot on 3 gallons of gas thats about 6.33 mpg at wot .

 

[steelespike]

Re: Small boat MPG?

A 15 will use about 1.5 gallons at wot a 20 would use about 2 gallons.
At 3/4 it's difficult to know what exactly it would use.
a 76 mile trip at 20 mph wot with the 20hp is 10 mpg.
About 8 gallons of gas.without a flow meter it is diffucult to know exactly what speed produces the best mpg.Under certain conditions a higher GPH might produce slightly better MPG because of the speed obtained.To be safe bring 2 tanks I think it is pretty sure your going to use at least 6 gallons.that would be over 12 mpg.

 

[Silvertip]

Re: Small boat MPG?

Stop thinking in terms of miles per gallon. You've been given the fuel flow rates for 10, 15, and 20 HP engines at wide open throttle. All you need to do is figure how fast each boat will be with the various engines. A 10 HP will need to run wide open to stay on plane and make any headway. At a burn rate of 1 gallon per hour you could go roughly 10 miles on each gallon. A 15 HP will burn roughly 1.50 g/hr but speed goes up to maybe 15-20 MPH. A 20 HP will burn 2.0 g/hr and speed will be in the 25 MPH range. So if you had to travel 40 miles, the 20 hp will get you there in 1.5 hrs and 3 gallons of gas. The 10 HP would take about 3 hours minimum and that equates to 3 gallons of gas. Isn't your time worth something? You burn roughly the same amount of fuel with the small engine as you do the big one because you have to travel much longer than with the bigger motor.

 

[cobra 3.0]

Re: Small boat MPG?

In this size class, it isn't worth beating yourself over mpg. Other factors may come in to play. I love my 15. The 15 is the same size of a 10 and nearly as fast as the 20, and is far more portable, trollable, easier to start, and smoother.

I had an two stoke18 Merc (same size as the 25 Merc). Traded it in for a two stroke 15 Johnnyrude that is almost as fast in my 14ft aluminum boat and far more pleasant to use. I still have the engine and I'm never changing it for anything else. I even used it to knee board last year when my 3.0 blew the head gasket and manifold gasket! It's plenty of grunt in a small package.

Two stroke 20's are often the same size as 25's and some 30's.

 

[River - Runner]

Re: Small boat MPG?

My 16 footer only gets around 2mpg. :'( I know that's kind of vague but I don't have anything in particular picked out yet....

38 miles one way is a long trip. You might want to consider remote streering on the boat for more comfort. My 25 hp. and 40 hp. get about the same mpg. With a light aluminum boat, a narrow boat will give a smoother ride in rough water and with a round (soft) chine it cuts through choppy waters. The 25 is better for all around use, but the 40 is best for traveling with the weight and speed.

A 20 hp. motor on a small tinny will make it scoot, but long distance traveling on rough water can get tiresome. With a good setup and nice weather it's an enjoyable trip.

A rear pic of my narrow 4 1/2 ft. beam, 14' FD Alumacraft, rated for 40 hp. The boat can easily handle the power. With a light load my 4 hp. motor will plane the boat.

A pictured 14' FD Alumacraft with 2 Mercury Mark 55's on the transom, courtesy of vintagealumacraft.

 

[ZmOz]

Re: Small boat MPG?

Isn't your time worth something?

The point of a boat like this is not to get anywhere in a hurry. That's why I have a ski boat that does 60+.

You burn roughly the same amount of fuel with the small engine as you do the big one because you have to travel much longer than with the bigger motor.

In theory, yes, but in practice, often no. A small motor running at WOT is less efficient than a bigger motor not running at WOT.

Right now I'm looking at importing a chinese made diesel outboard...but I think I might have to bribe somebody at the EPA. :devil:

 

[ZmOz]

Re: Small boat MPG?

A pictured 14' FD Alumacraft with 2 Mercury Mark 55's on the transom, courtesy of vintagealumacraft.

Now THAT'S cool! 8)

 

[Silvertip]

Re: Small boat MPG?

ZMOZ -- You are all over the place in this discussion. Although fuel economy seems to be your biggest issue, travel time does not seem to be an issue, yet it is key factor in determining how much fuel you use to reach a given point. If you aren't in a hurry then put a 10 or 15 HP on the boat and be done with it. Fuel flow will be about 1 - 1.5 gallons per hour at wide open throttle and about 15% less (maybe) if the boat stays on plane at lesser throttle settings. If you troll a lot, that's still a good solution.