1973 Johnson 20 hp

[motorhelp]

My motor was starting to run poorly. It would always start fine, then it started to cough and die when I would close down <br />the thottle after a full speed jaunt. The eventually it would start missing. first at full throttle , then at part throttle. I rebuilt the<br />carb and it ran absolutly perfect. Didn't skip a beat. 2 weeks later I took it out and it started <br />running poorly the same as before. It has a newer fuel pump and new fuel line fittings. compresion is text book perfect and both<br />cylinders are identical. spark plugs look good. I am assuming it is a fuel related problem. Does anyone have any ideas what could be the<br />culprit? I am trying to get it running good so it is ready next spring. thanks John

 

[The Marine Doctor]

Re: 1973 Johnson 20 hp

When was the last time anyone had a look at the points?<br /><br />TMD

 

[motorhelp]

Re: 1973 Johnson 20 hp

The points are good, I pumped up the fuel line and I was wondering how long it should hold presure. It doesn't hold presure for more than 15 seconds. ( hard fuel line bulb) I spent 65 dollars 2 years ago to find out I had a bad tank fitting. It seems to me that fuel line fittings have a short life span. Any comment greatley appreciated.<br /> John

 

[Joe Reeves]

Re: 1973 Johnson 20 hp

John.... Double check the carburetor. Since the engine ran fine for a time after you reworked the carb, there is a possibility that one of the fuel lines is deteriorating internally, allowing extremely small pieces of debris enter the carb (worth looking at).<br /><br />Note... The fuel bulb is designed to be hard only when you prime it, not when the engine is running. If a fuel connector is leaking anywhere, that should be obvious.

 

[motorhelp]

Re: 1973 Johnson 20 hp

I will change the fuel line. I changed all the fuel lines about 9 years ago so it is due. Should I put an inline fuel filter somewhere under the hood? The bad fuel line fitting didn't leak.