tank of fuel in 20 min?

[chuckshepard]

got one for ya...1984 evinrude 25 hp outboard motor. i have a 3 gal plastic gas can, filled with a 40:1 ratio. when i give the motor full throttle it uses a half a tank of gas in approx. 5 min. choke appears functional, new plugs hoses dont appear to be leaking. no sign of visual leaks. what kind of fuel consumption should this motor get?

 

[hooterville]

Re: tank of fuel in 20 min?

sounds like alot for a small outboard. what kind of boat?

 

[tashasdaddy]

Re: tank of fuel in 20 min?

2.5 gallons per hour, at wot. you have a leak somewhere. you should run 50-1 oem recommendations.

 

[chuckshepard]

Re: tank of fuel in 20 min?

16 ft deep v speedboat converted to a fishing boat.

 

[chuckshepard]

Re: tank of fuel in 20 min?

any way of checking for leaks without running the motor? when i hook up the tank to the motor while not running and pump the bulb the system becomes pressurized but does not leak.

 

[kenmyfam]

Re: tank of fuel in 20 min?

way to much fuel and the wrong mix. 50:1 is the recommended as far as I know.

 

[jtexas]

Re: tank of fuel in 20 min?

fiberglass boat? does it get on plane at all? sounds like a pretty inefficient setup. pushing a lot of water around.

use your fish scale to weigh the fuel tank before & after, to get more precise measurement of fuel burned - could maybe be a perception problem? happens to me all the time, mis-estimate how much fuel left in portable tank.

if you can, get your hands on a tachometer, see what kind of RPM's it's making at WOT.

pressurize the line, tilt the motor up far as it will go and see if any fuel runs out the carb throat(s).

What do the plugs look like after its been running awhile?

 

[chuckshepard]

Re: tank of fuel in 20 min?

boat is aluminum. it actually is professonally rhino lined on the bottom. pretty quick, she will go about thirty mph im guessing. fuel tank has a gauge and im fairly sure its accurate. plugs were just changed after two seasons. they were moderately worn and black at the electrode. I DO always tilt my motor up after use and it always appears there is fuel leaking directly out of the carb.

 

[jtexas]

Re: tank of fuel in 20 min?

ok, I take back any implication it might be underpowered, I was envisioning a big ol' ski boat....

But hey, there's your problem you're leaking fuel from the carb float valve(s).

If its been a few years since your last carb rebuild, this would be a good time, including new valves & seats. If its been more recent, check the float height. You can test the float valve operation by blowing through the fuel inlet (best to remove carb from engine and drain the bowl first ); held upside down, no air should pass; held rightside up, should be very little resistance.

 

[chuckshepard]

Re: tank of fuel in 20 min?

have never really rebuilt a carb before, is it difficult? i am assuming it is cost effecient. do you know of a good place to get a rebuild kit? oh yeah, that i know of the carb has never been rebuilt.

 

[iwombat]

Re: tank of fuel in 20 min?

right here on iboats, your Napa dealer, or your johnurude dealer. Only the OEM kits (at the dealer) will have a replacement float. You may or may not need that, but since you're having float problems it's probably a good idea to get the OEM kit.

It's not hard at all, and certainly a screwdriver-competent newb mechanic can tackle it. With a little help from this group of folks you're not gonna go wrong.

 

[jtexas]

Re: tank of fuel in 20 min?

it's a remarkably simple device - I always use the sierra brand kits from iboats - a service manual would be a good idea, pay for itself really, since a shop will charge $95 to $130 per carburetor, do it yourself for about $12 plus the cost of the carb cleaner. You can get a kit with a float or one without - you don't need the new float unless the old one is saturated & not floating - very unlikely.

remove, disassemble, soak overnight in carb cleaner (I use berrymans b-12), blow through orfices with compressed air (or aerosol carb cleaner), reassemble with new kits, reinstall.

See the Engine FAQ section of iboats, a joe reeves thread titled something like "setting carb mixture screws". that's about it.

 

[chuckshepard]

Re: tank of fuel in 20 min?

thanks alot for the help everyone. going to look into rebuild kits now!!

 

[hamburgerman]

Re: tank of fuel in 20 min?

Did you say that you have rhino liner sprayed on the bottom of your boat.Like on the bed of a truck oir somthing I have'nt heard of.

 

[chuckshepard]

Re: tank of fuel in 20 min?

yes, its not exactly rhino liner. not the spray on crap. the guy i bought the boat from had it done professionally at a auto body shop....some special type of liner that is chemically adhered to the bottom of the boat. it no longer leaks and when wet the liner is slippery as hell. it also moves better on the water. it is actually a pretty sweet set up.

 

[wbeaton]

Re: tank of fuel in 20 min?

I've wondered how well those liners would work for sealing leaks. How long have you had it on your boat?

You've already got the carb responses so I won't add to that. My 1988 Johnson 30 hp gets about two hours WOT to a 6 gallon tank of gas. I can usually get a full day or more out of a tank when I'm fishing. Just depends how much travelling and trolling I do.

 

[reload]

Re: tank of fuel in 20 min?

You could not push that much fuel through a needle valve orfice in five minutes. Thats 1.15 cubic inches per second. Can't happen.

About 1 gallon per hour per 10 hp is normal.

 

[wbeaton]

Re: tank of fuel in 20 min?

That's true, reload. I suspect it just seems like its a tank in 20 minutes. I have a 3 gallon tank as my reserve and it doesn't take much running time to make the gas disappear. Once you hit the bottom third it looks like you're on empty.