1985 Johnson 20 HP Cuts Out Under Power?

[GPSSHOOTERS]

I have an 1985 Johnson 20 HP that dies under power. I can be running along at full speed and it will just die down but not cut off. This is just temporary and can get back up top full speed and it will do it again in a minute or two.<br />I have a new tank and bulb and recently rebuilt the carb but it still does this.<br />Any ideas?<br />Tommy<br />GPSS<br /><br />www.georgiaprecision.com

 

[JB]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

Howdy, GPSS.<br /><br />Is this a 1985 Johnny of undisclosed HP, or is it an 85HP Johnny of undisclosed year?<br /><br />Would make a difference, either way.

 

[Yepblaze]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

Did you replace the fuel line connector? Thay can sometimes be problamatic, what with a leaky oring.<br /><br />Check, or change fuel filter or fuel pump for problem.<br /><br />Carb may need more thorough cleaning. May have hardened deposits in jets restricting flow. Or just plugged again.<br /><br />Then there is always the possability that it could be ignition related. Procedure to isolate that might be unit specific and require more data about what 85 Johnson it is.

 

[GPSSHOOTERS]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

It is a 20 HP, sorry , I left that out.<br />I am a "Newbie".<br />Tommy<br />GPSS

 

[jim dozier]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

When it starts to die, does it do it suddenly and crisply like you are losing a cylinder (ignition) or does it do it gently like you are cutting off its mixture (fuel supply)?

 

[GPSSHOOTERS]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

It is sudden. Almost like dropping to idle speed. <br />It will then usually spit, and then you can throttle back up to full power again.<br />Tommy

 

[jim dozier]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

Its hard to tell from your description but sounds more like a fuel supply problem, I would start checking the fuel lines first. When it happens have you tried pumping the fuel bulb? If that helps that usually points to the fuel pump. When it happens does temporarily choking help? Check you fuel tank vent (line or cap). If you can borrow another portable tank, see if it happens with that. You gotta narrow this down a bit.

 

[GPSSHOOTERS]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

I am going out today and will try some of the things you mentioned. I am recutting and reclamping the gas connections now to be sure they are tight.<br />Is the vent supposed to be opened or closed?<br />Tommy

 

[jim dozier]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

Vent must be open during operation. Is yours a portable tank or fixed location?

 

[GPSSHOOTERS]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

Portable, Open is what I use. I just wanted to be sure.<br />Tommy

 

[GPSSHOOTERS]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

Alright, It happened one time yesterday. As it was happening, I grabbed the bulb and pumped it, it seemed to have full pressure on it and did not help any. The engine did not cut all the way out, just dropped from wide open to about idle speed for just a moment, then I was able to throttle back up and continue on. <br />I ran about 3 miles total yesaterday with a Fresh Fuel mixture, new clamps on the hose and this is a new tank I bought lastyear.<br />Any Ideas?<br />GPSS

 

[jim dozier]

Re: 1985 Johnson 20 HP Cuts Out Under Power?

Odd, but I am still guessing fuel starvation. Perhaps the carb float is occasionally sticking closed and then coming unstuck. Next time it does it spray some pre-mix oil/gas in the carb throat and see if it picks up. When you rebuilt the carb did you put in new float needle valve or just clean it? Even if you put a new one in it could still be sticking.