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1977 55 hp Johnson surging at WOT

M

mudhunter

New member
Hello~
A quick history on the motor; bought a few years back from a guy, it did run but the prop wouldn't turn in either forward or reverse. The engine sat for a while, then I finally had some time this spring to disassemble the lower unit and see what was what. Well, turns out the pinion gear and the forward gear were mush. So, with all new parts I was able to completely rebuild the lower unit and get that back on. I have also installed a new fuel pump and rebuilt both carbs, and new spark plugs too. Any history beyond that, I have no idea. The motor runs very good at low and mid range RPM's, however when I go WOT after a few seconds, it surges for a few seconds then drops RPM's on it's own. If I back the throttle off, to a mid range or low range, the problem goes away until I go WOT again. I have searched the forums here and my best guess is that has something to do with timing? Any thoughts or advise would be greatly appreciated! I do have a video of it, but I couldn't figure how to upload to this site. I could email if that would help.
Thanks,
Chris.
 
Well----The timing on these motors is fixed at the factory.-----Owners generally should not attempt making adjustments.----Trying to change timing with the ---" Lets see what happens " if I turn this , just does not work.----Test run with another tank and hose.------
 
Good to know. I'll forget about messing with that then. Gas tank, hose and gas is brand new. Maybe I'll buy another tank and hose and try that. Perhaps re-do the carbs again and see if I can get the high speed jets out this time.
 
Test run with a timing light hooked to one cylinder at a time.----Observe the flashing light and look for possible spark issues.
 
The high speed jets ( orifice plugs ) are inside the carburetor bowl.-------Found way inside after taking the drain screw out.------A 3/16" diameter screwdriver may work or modify one to take them out.
 
racerone said:
The high speed jets ( orifice plugs ) are inside the carburetor bowl.-------Found way inside after taking the drain screw out.------A 3/16" diameter screwdriver may work or modify one to take them out.
Click to expand...

Yeah, those are the one's I think I couldn't get out. I'll take the carbs off again after work and try again. And these don't generally come in rebuild kits if I remember right?
 
racerone said:
The high speed jets ( orifice plugs ) are inside the carburetor bowl.-------Found way inside after taking the drain screw out.------A 3/16" diameter screwdriver may work or modify one to take them out.
Click to expand...

Thanks for the advice! They were both pretty gummed up. We'll see how she does today!
 
Well, after installing all new jets and new carb kits she purrs like a kitten. Took her out this morning on the river and im happy to say, problem solved! I can't thank you all enough for your wealth of information and wisdom.
 
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