Johnson 55HP fuel consumption ?

[David Hills]

I have a Johnson 2 Cylnder 55 HP 1979 Outboard.It is on a Avon 13 foot SeaRider RIB. The fuel consumption seems excessive at tick-over /idle.<br /><br />At a rough guess it using 4 litres/hr on tick over.<br /><br />Does anyone know what would be normal consumption figures for the above configuration and how you measure fuel consumption correctly?<br /><br />And what are the most likly causes of excessive fuel consumption on this Outboard.(there is no marine growth on the hull)<br /><br />many Thanks<br /><br />Dave Hills

 

[steelespike]

Re: Johnson 55HP fuel consumption ?

Does the motor perform normally otherwise?<br /> What is the speed at idle?<br />If the motor is sound check the fuel pump diaphram<br /> for a hole. Be sure the carb float(s) are working right.

 

[papasage]

Re: Johnson 55HP fuel consumption ?

david i have a 79 55hp . had to replace the fuelpump it had a hole where the puls vacum hole is . when i pumped the ball up it would notpump tight . it was pumpinggass into the block .it would still run . set your trim to the best plain . to low or to high will put preasure on the enguin.those older motors do consume more gass than the new ones . probabley half as much.<br />it depends on the boat and the setup weight load.

 

[David Hills]

Re: Johnson 55HP fuel consumption ?

Thanks for the reply Papasage.When I pump the<br />hand primer it does not go tight.The engine runs pretty well at WOT and the fuel consumption while quite high is not excessive. At Idle I'm doing about 3 knots. This boat has 2 speeds only, 3 knots and the fast one (I dont know what the planing speed is yet, but it seems to go the same speed at half throttle all the way to full throttle).The avon searider has a flooding hull design for stability at very low speed, I am thinking about blocking off the flooding hull, and hope this will improve low speed a bit.<br /><br />Thanks for your Replys

 

[David Hills]

Re: Johnson 55HP fuel consumption ?

I've changed the diaphram,it was well shot, but the hand bulb still does not pump up hard.Fuel comes out the carbs air intakes and what looks like a over flow pipe. Is it likely that the needle values the come of the float to stop fuel could have a problem? Its twin carb so I can Isolate fuel to each one and test?<br /><br />Thanks Dave

 

[papasage]

Re: Johnson 55HP fuel consumption ?

david i pulled the carbs off my boat left them hooked to the gas line pumped the bulb the gas still came out of the block that is how i could tell that the diafram was bad if you replaced that it would have to be the carbs.fluddid hull more weight more gass .