1960 Evinrude FastTwin 18hp excessive fuel consumption

[Motor Boater Bill]

Just back from a six day fishing trip with three boats among us. My 1976 Merc 20 hp, a 1956 Evinrude 15 hp and a 1960 Evinrude FastTwin 18 hp. The 18 used twice as much fuel, if not more, than the other two. The 18 is a recent addition to the "fleet" so we don't have any historical data on it. We ran about the same time/distance in all three boats. I was not on board so I can't say much about performance, but it seemed to be similar to the 15. No fuel was seen leaking externally at idle, but it was not visually inpected at WOT or immediately after (I know, should have, not my boat). Fuel was visible dripping from the leg after running. A lot of oil/scum seemed to accumulate in the test tank rinning it prior to the trip. Running 40:1 mix per Chinewalker's recommendation.<br /><br />There seem to be two possibilities--either it is leaking from the pressure side of the fuel circuit (didn't see it, but only observed at idle, pressure would be higher at WOT) or it has to be going through the engine, although it seems it would degrade performance pretty dramatically if it was that rich. Again, I was not on board the boat and we don't have historical data to compare, so I can't attest to the performance. <br /><br />One other note, the fuel lines were replaced before we got this motor and fastened with zip ties, not clamps. I found that suspect, but again was not able to observe them to be leaking. It is a fuel pump motor, not a pressurized tank. I don't know if that is original or retrofit on a 1960.<br /><br />Anybody got experience with this issue? Many thanks!

 

[Paul Moir]

Re: 1960 Evinrude FastTwin 18hp excessive fuel consumption

1960 models all had fuel pumps (except the gravity fed 3hp).<br /><br />There's two possible sources for extra fuel if you rule out outright leaking. One is the fuel pump and the other is the carburetor. The fuel pump is easy to check. Unscrew the two screws that attach it to the engine and loosen it off. Then pump the primer bulb and observe if any fuel leaks out the small hole in the back of it.<br /><br />If that checks out, it's on to the carburetor. Possibilities include leaking needle & seat, improperly adjusted float, sunk float, leaking gaskets. All these things can be rectified with a carb kit.<br /><br />Finally, your '60 ought to have adjustable high speed and low speed mixture controls. Were they adjusted properly?

 

[Motor Boater Bill]

Re: 1960 Evinrude FastTwin 18hp excessive fuel consumption

Thanks Paul--I was not in the boat, so I adjusted the idle screw in the test tank prior to the trip, but no adjustments were made to the high speed jet, as the operator did not want to mess it up and it was, after all, running, and we were, after all, fishing, so burning extra fuel was a lower priority at the time! As the owner/operator is a novice with outboards, he may have been better off not trying to adjust it. All that said, I think he and I need to go out and run it so I can do the high speed adjustment. I am wondering if that could account for this much excess fuel use and still run OK. I am a Merc guy, and my motors have had fixed high speed jets, so I'm new to the high speed adjustment drill. I'll get the insructions off this board--I've seen them posted here.

 

[Rick K]

Re: 1960 Evinrude FastTwin 18hp excessive fuel consumption

Bill, I have a '59 Johnson 18. It is an absolute HOG on gas at WOT. I go thru 6 gallons in less than an afternoon.<br /><br />As Paul said, check the fuel mixture controls. Both should be drawn in, then loosened 1.5 turns. Tweak from there. <br /><br />I have zip ties on my fuel lines - no issues. The oil/gas mix is just burn off, they're noted for that. <br /><br />If you were leaking, you'd know it. My carb-bowl gasket was leaking. One day ran perfect, next day ran terrible. <br /> <br />If you have no historical data on it, perhaps a tune up, decarb, etc., will help somewhat.<br /><br />Good luck,<br />Rick

 

[Paul Moir]

Re: 1960 Evinrude FastTwin 18hp excessive fuel consumption

If the high speed control isn't adjusted, it will certainly be a gas hog. I find 1 turn out as an initial setting on the control is sufficient, and I usually end up somewhere around 3/8 to half a turn out after adjustment. Always err slightly rich since gas is cheaper than pistons.

 

[Motor Boater Bill]

Re: 1960 Evinrude FastTwin 18hp excessive fuel consumption

Gentlemen, thank you. I will try to get him out on a lake where we can dink around with the high speed settings. Our recent trip was on the Cumberland River with rapids, gravel bars, submerged rocks, floating logs, etc--not the best place for high speed test runs!<br /><br />Once adjusted, and assuming no other problems, is it reasonable to expect the 1960 FastTwin 18 to be close to the 1956 15 hp in fuel consumption, or do the extra three ponies drink their weight in gas?<br /><br />Again, thanks for the help.

 

[Paul Moir]

Re: 1960 Evinrude FastTwin 18hp excessive fuel consumption

I'll qualify this by saying "for their time"!<br /><br />For their time the 18hp was pretty miserly on gas. I wouldn't be surprised if it did much better than your 15hp. Unless running at WOT. There's a big difference in consumption with all these outboards between about 3/4 and full throttle.

 

[Motor Boater Bill]

Re: 1960 Evinrude FastTwin 18hp excessive fuel consumption

I'd say if anything, the 15 FastTwin was run wide open more of the time than the 18, just because the guy with the 15 is more accustomed to his boat. So, all the more reason to assume there is something amiss with the 18. We'll start with adjusting the high speed jet and take it from there. <br /><br />I emailed the owner of the 18 this afternoon, and he agreed that we will have to go out to some lake after work some day soon, and probably have to fish some also. Doggone it. All this diagnostic work to do...