Johnson Fuel trouble? Help!!

wtpoperator

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May 15, 2005
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I have a 2001 Johnson 70 HP motor on a 2001 19' Lowe roughneck boat. I purchased the unit last fall from a couple getting a divorce. They had used it only once the previous year and 4 times the year before. We had a real hard time starting it when I went to look at it origionally. I checked the compression and it was fine. I brought it home, ran sea foam through it and had no problems. The other day I was out and it ran great then for no apparent reason it just seemed to bog down. I got it back and checked the plugs for spark and/or fouling. They were all fine. We drained the bowls thinking maybe something was in the gas. The next day we checked compression again (all 3 cylinders were good thankfully), put the muffs on it and started it up. It ran fine. I decided to take it out again yesterday and it ran great for about 15 minutes. Then it started to run slow again. If I would keep choking it, it would run full speed. My ball does seem 1/4 to 1/2 flat (definately not tight) but it doesn't help to keep pumping it up. It just seems to be not getting enough fuel. My assumptions are the filter may have junk in it or the fuel line or tank may be sucking air. What do you guys think. Should I try replacing those items or just bring it in to get serviced. My thinking is since it sat over night and then ran good agin it may be just not getting enough fuel for some reason. It does start fine and idles fine, it just doesn't have any top end power. I have no problem just motoring around at the low speeds.<br />Thanks!<br />Brent
 

R.Johnson

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Sep 24, 2003
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Re: Johnson Fuel trouble? Help!!

If it is sucking the ball flat, take a look at the anti-siphon valve if it has a built in tank. If it has a built in tank, try running it on a portable 6 gal.
 

R.Johnson

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Sep 24, 2003
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4,446
Re: Johnson Fuel trouble? Help!!

If it is sucking the ball flat, take a look at the anti-siphon valve if it has a built in tank. If it has a built in tank, try running it on a portable 6 gal.
 

wtpoperator

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Re: Johnson Fuel trouble? Help!!

It isn't sucking the ball flat. It is simply a little soft. It is currently running on a portable 13 gallon tank.
 

R.Johnson

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Re: Johnson Fuel trouble? Help!!

What kind of connection on the 13 gal. tank?
 

Solittle

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Apr 28, 2002
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Re: Johnson Fuel trouble? Help!!

Bet you have crud in the carbs & time for a thorough rebuild of the carbs with new kits. It is a strait forward job for the average driveway wrench if you have never done it before. Go to the red search at the top of the page and read away for the how to's.
 

wtpoperator

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May 15, 2005
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Re: Johnson Fuel trouble? Help!!

The connection to the tank is a barb fitting with a hose clamp style fitting. I figured maybe I needed to tear into the carbs and clean them up. We started to work on that project and they looked ok with the little bit of stuff we took off. We then put the carbs back together and decided to make sure compression was ok. I was pretty sure it would be fine because I tried to look at each cylinder as I checked the plugs. Each cylinder was at 150 psi. I will check into the how to's and start with the carbs.<br />Thanks!<br />Brent
 

R.Johnson

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Sep 24, 2003
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4,446
Re: Johnson Fuel trouble? Help!!

I would still try running it on a 6 gal. remote tank. I'm betting that barb on your 13 gal. tank is an anti- siphon valve. Unscrew it, and see.
 
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