Losing power - 40 HP Johnson - Need Help!!

[Haverb]

I have a '92 Johnson 40 HP on a pontoon. Besides difficulty starting, I lose power after accelerating past 1/2 power. The motor backs down and won't go past about 1/2 power. I can get more power by continuing to press the chock valve on my key switch, but it reverts to 1/2 power as soon as I stop that. I had this problem a few years ago and solved it by replacing the plugs. This motor apparently has resistive plugs that can be interfered with if defective. <br />I have replaced the plugs and the fuel filter with no change in performance. I'm stumped! Can anyone help!!! Thanks.

 

[JB]

Re: Losing power - 40 HP Johnson - Need Help!!

Ahoy, Haverb. Your engine is starving for fuel. Possible causes start at the fuel tank pickup, primer ball, fuel lines, and the most likely suspect is the fuel pump, with the carbs also possible, but less likely.<br /><br />An overhaul kit for your fuel pump is inexpensive and simple to install. Buy 2. As long as you have a spare kit aboard it will never fail again.<br /><br />Bon Voyage.<br />JB

 

[MooseMan]

Re: Losing power - 40 HP Johnson - Need Help!!

Hi - JB is most likely correct about the fuel pump. I would suggest driving it and rather than choking it have someone pump the primer bulb. If the fuel pump is bad it should go limp immediately after priming it and priming it will give the engine life. <br /><br />Contrary to JB however I would highly recommend against a fuel pump rebuild kit. Just get the pump. All the mechanics I know hate the kit - people end up spending more money in labor to put the thing together than the pump is new. And you should be able to easily do the repair yourself.