help me fix my outboard!!!

[colinwcolclough]

Hi there outboard experts. Who can help me with this one? I have a 1987 johnson 70hp 2T outboard with intermittent problem. Keep loosing power - application of electric choke helps if I rapidly switch choke on and off when problem occurs. Me thinks fuel air mix problem. Have rebuilt carbs, checked for air leaks throughout fuel system. Now noticed compression down 20psi on #1 cylinder and spark plug has grey deposits. Any ideas gratefully received. PS, don't want to scrap engine as it was donated and have promised to use it.
Many thanks
Colin

 

[Lakesailor]

Well there are 51,000 threads on this Johnson Forum. Many of them are concerned with your problem. There is a Search facility, but it's a bit scatty.
I had a problem on the same motor and found the answer eventually.
20 psi isn't a huge difference. Anything over 100 is OK. Were you cranking with all the plugs out?
The fact it works when you apply the choke (primer solenoid) points to blocked or gummed up jets. Have you tried pumping the primer bulb when the problem occurs? The carbs are super simple, did you sync and link properly when you reassembled the linkage? It could be something as simple as air leaking into the fuel system (on the suction side, more difficult to find than fuel leaking out) and creating an air lock in the fuel delivery pipes, the top carb being susceptable. Or the bottom float chamber flooding and starving the top carbs (I had that when the drain plug on the bottom carb came loose.)
Do you have the VRO working or have you dumped it and pre-mix? Air leaks on the fuel side can cause all sorts of oil ratio problems.
But your symptoms point to a carb problem. Later motor have a system called S.L.O.W. which knocks the revs back to about 2500 if there is an oil pump or overheat problem.

There is one thread on the forum with a guy with your problem. He cleaned the carbs twice and no change, then really went to work on poking out the jets (only use very soft wire or you'll alter the jet apperture)
"At any rate, after playing around poking and spraying and such, a little (1/8" dia or so) glob of white crystalized junk came falling out of one of the carbs--not sure exactly where it came from, but it came out. Thought that might be a good sign, so I put the motor back together and took it out...And low and behold it runs beautiful!Thanks to everyone for their help!!!John W"

 

[machurley22]

Not a bad answer but 17 minutes.. Tsk! Tsk! Were you out in the garage?

 

[Lakesailor]

Sorting out a flat battery. /forums/images/graemlins/grin.gif