1994 Johnson 120 V4 low power at first, let sit then runs great

[Peacock]

I have a 1990 20 ft Bayliner Capri, with a 1994 Johnson 120 V4, it will crank, idle and run, it runs at half power at first then after turning off or idleing for a few min it will run like a bat out of hell all day if I don't stop, plugs, coils, fulelines, fuel additive, and plug wires replaced. I have heard that removing the oil injection unit and mixing my own gas might help.<br />Motor is in pristine condition, good compression, low hours, has to be simple if it can run so good when it wants to. Any tips on this engine will be greatly appreciated

 

[DJ]

Re: 1994 Johnson 120 V4 low power at first, let sit then runs great

Mixing your own gas will NOT help.<br /><br />The engine is not using all four cylinders if power is down. It's missing something. Spark, fuel, air. You'll have to tell us which one it is.

 

[Peacock]

Re: 1994 Johnson 120 V4 low power at first, let sit then runs great

Hard to tell, carbs are clean, it runs so good when it kicks in after a quick stop, plugs look ok, can coils cause this? do they "start" to go bad or just burn out?

 

[BillP]

Re: 1994 Johnson 120 V4 low power at first, let sit then runs great

Mixing your own oil won't hurt either unless it is massively over oiled. Even double oil won't do this until many, many hrs of running. Coils generally do this stuff when hot. Stators are another story and do it anytime.<br /><br />The fuel pump diaphragm may be loosing prime and then catching up. Have you tried pumping the bulb when it is down on power? If pumping the bulb helps I'd say it is at the fuel pump diaphragm, restricted filter or restricted fuel line.