bad fuel economy

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bad fuel economy

Postby mdfowlman » Wed Sep 11, 2013 8:17 pm

So I have 1860 wareagle with a 1997 2stroke johnson 50hp. I only get about 1 mile per gallon when under full throttle is this as crazy as I think it is. If so what could be the cause? Im thinking maybe the air fuel mix is off but im probably way off
Thanks fellas
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Re: bad fuel economy

Postby ErieAngler » Wed Sep 11, 2013 8:20 pm

Too little motor for the boat. I have the same rig with a 115, personally I think 90 is about perfect but anything less than 70 is too small for that boat IMO.
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Re: bad fuel economy

Postby mdfowlman » Wed Sep 11, 2013 8:28 pm

I agree its underpowered but 1 mpg is crazy
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Re: bad fuel economy

Postby gahunter706 » Wed Sep 11, 2013 8:48 pm

1mpg doesn't sound right, but I don't thinks its because of too little motor. I have a 1756 with a '98 Merc 40 2stroke and it is pretty decent on gas. The other day me and a buddy went scouting for geese and we rode around for about 2 hours, with most of that being full throttle, and only used about 5-6 gallons of gas. Even when I used it for bowfishing with a deck, 5 batteries, and 4 guys on the boat, I only had to put in about $5 each night. How did you actually calculate the mpg you were getting?
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Re: bad fuel economy

Postby QuackerSmacker498 » Wed Sep 11, 2013 10:22 pm

Yep, that's crappy mileage. My 20 foot fish rite with a 460 gets a little better than that not much. But its 330hp.

Any ways, did the boat ever get about 3-4 mpg. Check your basics. Plugs, fuel oil mixture, is the boat properly trimmed? Too much weight.....I do agree you are way under powered for that boat.
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Re: bad fuel economy

Postby mdfowlman » Thu Sep 12, 2013 4:00 am

I make a 5.5mile run out in the bay to an island to hunt and. My six gallon tank is almost dry when I get there. Plugs r new. How do I che k the air to fuel ratio
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Re: bad fuel economy

Postby BT Justice » Thu Sep 12, 2013 4:50 am

One of my hunting partners has the same boat with a 90 hp Merc 4 stroke, with 4 guys and gear in the boat going upriver it strains a bit to get the job done. Your below the minimum HP rating for that boat(60) and pushing a 2 stroke at full throttle.
I agree if you are getting that bad a fuel mileage something may be wrong, however you have to look at what the obvious cause is, an engine that is constantly pushed to the limit just to push your boat.
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Re: bad fuel economy

Postby Cajunwannabe » Thu Sep 12, 2013 7:41 pm

What pitch prop are you running and what are your rpms at "full throttle"?

A larger pitch prop might give you might give you better top end speed while turning less rpms = better mpg.
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Re: bad fuel economy

Postby QuackerSmacker498 » Thu Sep 12, 2013 9:09 pm

Fowl man to give you a ball park idea on fuel consumption. I pushed a 16.5 boat with an 84 mercury 50 HP. Three guys all our crap, a dog, 30 decoys, 20 gallon fuel tank, and two batteries a minimum of 14 miles per trip. On average, I would burn about 4-5 gallons. It varied depending how much extra scouting I did. That motor was sluggish with that kind of load. I have since gone to 1978 Johnson 70 HP. With same conditions, I only burn about .5 - 1 gallon per trip. I would assume your boat is greatly under powered and is fighting hard to maintain the upper rpm range.

Theres lots of way you can spend your money in your predicament. As most people said, you need to look at 90 HP for that size boat. Then probably assess your fuel consumption issues. Is this a tiller or remote motor?
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Re: bad fuel economy

Postby mdfowlman » Thu Sep 12, 2013 9:09 pm

Honestly no clue on the pitch it was on the motor when I bought the boat
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Re: bad fuel economy

Postby QuackerSmacker498 » Thu Sep 12, 2013 9:12 pm

Sorry, .5-1 gallon more per trip for that 14 mile run.
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Re: bad fuel economy

Postby lukepaige » Thu Sep 12, 2013 9:20 pm

Used to have a 17 foot aluminum hull with evinrude 120 hp carbed 2 stroker that got 1 mile to the gallon. I know how it feels! That boat wAs not under powered the motor just sucked down the gas. Get yourself a 4 stroke you will be pleasantly surprised.
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Re: bad fuel economy

Postby mdfowlman » Fri Sep 13, 2013 5:56 am

I called my boat mechanic yesterday afternoon and he informed me that these motors are gas hogs he said that this motor will burn up a6 gallon tank on Idle in an 8 hour day at the shop. I want a motor that's going to be a lot more fuel efficient because this year I'm going to make a lot of 10 and 15 mile one way runs out to a few islands I know of but I'm in the process of buying a new house so the motor goes on the back burner I guess I can get a new 4-stroke next year
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Re: bad fuel economy

Postby Boatman » Fri Sep 13, 2013 7:02 am

mdfowlman wrote:Honestly no clue on the pitch it was on the motor when I bought the boat


This is your problem. You can probably double your gas mileage with the proper set up between boat-load and propeller. Do you have a tach? If not get one or borrow one to set the motor up to your boat. If your motor is only turning say 4000 rpm at full throttle and it should turn 5500 rpm you are running more fuel through the motor than it can burn and wasting fuel. Not to mention damage to the motor by doing this. At full throttle your motor should turn 5500 rpm. You should be able to keep the boat on plane at 4000 rpm (not full throttle)with the right prop and that will improve your mileage greatly.
There are still things worth dying for and 1 of those things is freedom.

I love Geese

Genesis 27:3 Now then, get your weapons, quiver and bow, go out in the fields and hunt some wild game for me.
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Re: bad fuel economy

Postby T Man » Fri Sep 13, 2013 10:50 am

There are a few factors that are not mentioned here that can greatly affect fuel mileage

1) Current. Speed over water and speed over land are 2 completely different things. These both translate to distance over water and distance over land. If I am going up river against a 6mph current, I may be running 22mph over land, but my boat is actually going 28mph. In simpler terms, boats will be less effective against the current than with it, resulting in more fuel burned. The only way to accurately measure sow is with a paddle wheel. Gps tells you speed over land only.

2) Load. A 50hp motor on a welded boat is a bit undersized as it is, but what else do you have in the boat? Greater displacement=more wetted surface. More wetted surface=more resistance. The resistance of water increases exponentially with speed.
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Re: bad fuel economy

Postby mdfowlman » Fri Sep 13, 2013 7:14 pm

Boat has a tach and reads 5500rpms. At full throttle. How do I choose the correct prop
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Re: bad fuel economy

Postby T Man » Fri Sep 13, 2013 11:13 pm

mdfowlman wrote:Boat has a tach and reads 5500rpms. At full throttle. How do I choose the correct prop



RPM sounds about right. What speed are you running at wot?
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Re: bad fuel economy

Postby mdfowlman » Sat Sep 14, 2013 9:19 am

Just the dog and myself in the boat it reads 30-31 mph
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Re: bad fuel economy

Postby Boatman » Sat Sep 14, 2013 9:43 am

What shape is current prop, and what pitch and diameter? Do you have power trim? Does boat plane off fast or slow? Check your motor height, cavitation plate should be even or a little above the bottom of boat. Check your weight distribution, the more bow of the boat you can get out of the water the less drag, and better fuel economy. If all checks out I would go with more pitch on the prop to get the rpm's down and better fuel economy. Full throttle operating range is 4500-5500 and rated HP at 5000rpm.
There are still things worth dying for and 1 of those things is freedom.

I love Geese

Genesis 27:3 Now then, get your weapons, quiver and bow, go out in the fields and hunt some wild game for me.
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Re: bad fuel economy

Postby Boatman » Sat Sep 14, 2013 9:47 am

mdfowlman wrote:Just the dog and myself in the boat it reads 30-31 mph


That's not bad for a 50 on that boat. Maybe try going a little slower for better fuel economy. With a big load you will probably be down to 5000 rpm.
There are still things worth dying for and 1 of those things is freedom.

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Genesis 27:3 Now then, get your weapons, quiver and bow, go out in the fields and hunt some wild game for me.
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