Got another problem with an older Johnson I can't find in the manual

[leesumm]

This motor is fairly new to me for about 2 months now and a work in progress trying to get it going. Its a 1977 70 hp Johnson . I thought after a new switch and a broken kill wire in the harness to the engine it was doing ok. It has been running fine except its hard to to get going at first without a few minutes on high idle and warming up then its fine thru the rest of the day. Today my cousin and I were out for a day of fishing and after warming up as always pulled away from the ramp into the middle of the lake and gave it the gas. Ran fine for a couple of minutes then sounded like it was running out of gas. Checked all the fuel lines and connections and the screen on the screw off filter. All good. Started it up and ran fine on low idle and put it in gear , all good untill I gave it gas then same thing like running out of gas. This time I hit the choke and off it went for a sprint second then lost power and another hit on the choke and off it goes again for a sprint second.The primer bulb is hard as a rock, and yes a full tank. It idles fine in gear and goes a little more than a modest walk but it wont go up to a high idle without dying .
I am thinking fuel pump? Just sounds like its running out of gas on a higher throttle. In the past I have checked all spark, spark plugs and compression. All looks to be normal. Someone point me in the direction to look for another problem?

 

[Daviet]

Re: Got another problem with an older Johnson I can't find in the manual

Normally pumping the primer bulb will bypass a defective fuel pump. You might check the high speed orifices in the carbs, If you have one or two plugged or restricted it will cause your problem.

 

[leesumm]

Re: Got another problem with an older Johnson I can't find in the manual

ok, primer bulb is hard all the time , even after sitting for a period of time. This motor is baffling, about the time I think I have it going like its supposed to, something else pops up .

 

[Daviet]

Re: Got another problem with an older Johnson I can't find in the manual

You have to pump the primer bulb when it is acting up, if you have a defective fuel pump, it will force the fuel into the carbs and keep the engine running. As I said before, restricted or plugged high speed orifices will cause your problem.

 

[leesumm]

Re: Got another problem with an older Johnson I can't find in the manual

The jets were free and open with no restrictions. I couldn't find any debris or anything in the bottom of the bowls. What I did find tho was when I went to "pressurize" the fuel system I pumped and pumped on the primer bulb and I heard sounds like picking up air from some where. I am thinking the little hose in the fuel tank from the tank fitting is sucking air. The fuel coming from the pump to the carb had a lot of air in the lines before the bulb got hard.

 

[leesumm]

Re: Got another problem with an older Johnson I can't find in the manual

This is an update on the post.
I replaced all the fuel lines , found a cracked T in the fuel line from the middle to the 2 and 3 carbs. Replaced that , replaced the vacum line? to the fuel pump. Main fuel line from the pump to the middle carb had some cracks in it. Did find a little water in the bottom carb bowl. Put the hose on it and started on second spin , then died. Started up again and it sounded like a well oiled Singer Sewing machine. I hit the gas in gear and it roared . If it runs as good in water as on the hose this boat should fly now.