Fuel delivery problem for 4 hp mercury?

[duckaholic]

I have a 1973 Mercury 40 4 hp short shaft which cranks first or second pull and idles perfect. It will idle in forward and reverse for long periods of time (10 minutes). However, when put under load (throttled up) the little motor will run for a minute or two then shut down. I can pump the bulb until it is hard again and it will repeat the afore described. I have removed the carb, taken it apart, thoroughly cleaned the carb, reassembled, and the problem is unchanged. Is this potentially a fuel pump not suppling enough fuel? or a vacuum leak? All suggestions or recommendations to cure my ailing little motor would be appreciated.

 

[crem1]

Re: Fuel delivery problem for 4 hp mercury?

Since you looked after the carb, the next will be the fuel pump. Get a new pump kit for the engine(cheap)

 

[drorbuz]

Re: Fuel delivery problem for 4 hp mercury?

had the same problem with mercury
my problem was that evry time i put it in gear the engine choke and shut down
if its not one of the carb / fuel pump or one of the plugs
my problem was the cable is joined gas and gear
and every time i put it in gear the gas cable was pulled down shutting down my engine
my point is check the cables while in gear and gas only

 

[duckaholic]

Re: Fuel delivery problem for 4 hp mercury?

Thank you each for your quick responses. I am off to acquire a fuel pump for the little 4 hp. Don't think it is a cable problem since this is a single carb., single cyclinder tiller handle controlled motor. Will post results.

 

[Droll]

Re: Fuel delivery problem for 4 hp mercury?

Test the function of the check valves in the fuel pump too, a tiny foreign object can disturb their function ( not fully closing ), might work fine at idle and low rpm but not delivering enough fuel at load/higher rpm .

Had this problem on my Merc60... a tiny seed from a birch got caught in one of the valves... since it didn't seal, it didn't work as intended .


Arne Kjetil