40 hp not idling.

[boclatt]

Hello all. I am new to boat motors so excuse the newbie question. My father just handed down to me a '66 whaler with a 40 merc on it. It seems to have trouble idling.

The serial number on the motor is 3724521 so I assume it is a 72-74 model. It starts up fine and then as soon as you lower the throttle down it sputters and dies out. I was wondering if there is anything easy to look for before I try to rebuild the carb. It almost sounds like its missing but the timing is correct with new plugs and wires.

I will try and get a video or sound clip of it running soon for you guys to listen to.

Any and all help is very much appreciated.

 

[Coloradolakeboy]

Re: 40 hp not idling.

Yes there is... go to the repair and maintenance page (the one before the Merc page) and click on frequently asked questions. There you will find a thread on awakening a sleeping motor. There you go.... She's going to need some
TLC for a bit to get her going. Be patient, get the Merc Service Manual
(the Original) and you can revive her. Your questions based upon reading the manual, can easily be answered by the experts here (not me).

O.K. order the service manual, got it? In the mean time, change the hoses and fittings from the tank to the fuel pump. Everything, hoses, primer bulb and the 40 year old gas tank. It is the ethanol in the fuel that is the problem.

I suspect the reason she is sputtering out in gear is a clog in the carbs from the tank or fuel line breaking down or a bad diaphram in the fuel filter. Under load, there is not enough fuel to keep her going. DO NOT RUN HER LIKE THIS!
you could burn a piston as she is running too lean. Post up your progress and final success, we all learn from this.... Right?
Good Luck....
CLB

 

[boclatt]

Re: 40 hp not idling.

Thanks for the tips there! Hoping I can get this baby back in the water soon.

It has all new fuel lines, diaphragm, tank, you have it. It seems to be leaking a bit around the carburetor so I am just going to go ahead and rebuild it. I dont know the last time the carb was serviced.

The last time the boat was out running on the water was about ten years ago and she ran beautifully. Everyone keeps telling me to just get a newer 25 four stroke, but I can't give up the sound and power this motor creates.


Also, does the new fuel with all the ethanol in it affect the oil mixture or the performance on these older motors? I know it will cause more maintenance as it causes the rubber in the fuel system to break down faster.