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knocking noise?1985 20hp johnson

N

newyota

Regular Contributor
This 1985 20hp Johnson I got last summer is keeping me busy.Learnig a lot.This engine makes a noise that concerns me somewhat.Not sure what it is.The engine seems strong after using it last summer a few times.I did hear a noise at slower speeds I was not sure about and here at home running it on muffs I give it throttle, say above idle or half and and I hear a knock or something and see engine jerk like a miss,sounds like a metal sound but not sure, but it does not seem to do it at full throttle and seems fine at idle and do not hear it.Is this a miss?I have recently readjusted the slow speed screw due to having to replace the plastic retainer for it.It is set at about slightly over half open and all linkage adjustments are correct and had put new plugs in it after I bought it last summer.I do not have a compression gauge to check that, but may try and source one.Not sure if this could just be a lean issue and need to adjust it more?Not sure if running it on the water would make a difference or not.thanks
 
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Run it with the lower unit off and see if the noise goes away. You can run a hose to the copper pipe from the hose to give it cooling water.
 
So, if the noise goes away what does that mean?Broken tooth on a gear?If there was an issue with a tooth broken would I be able to tell by just turning it by hand?Has a new water pump in it.
 
If the noise goes away it may be in the lower unit. You might be able to feel it if you turn the drive shaft by hand remove the water pump for that. Do this test too pull the plugs and run the top piston just past TDC on the down stroke. Then take a wood dowel and push on the piston see if it moves or you hear a clunk. Repeat with the bottom cylinder. Tests need to be done.
 
Well, I just watched some Youtube Videos trying to find a engine issue someone posted like mine and I think I found it.A youtuber wanted to know "what the heck that clunk" was after a tune-up on an older Evinrude and it sounded like what I have.I found other videos sounding like mine.Seems they said it was a "LEAN SNEEZE".It shore sounds like the engine is coming apart if you never heard it before.When this blizzard clears I may try to adjust the slow speed screw out some more since that is when it happens to try to richen it up and see if that helps.Other causes someone said it could be a leaky gasket.
 
Have you checked engine sync between throttle opening and spark advance? On your engine there are two marks on the throttle cam, line the follower roller center of the two marks and loosen the clamp screw for the throttle shaft on the carb. hold the roller up tight to the cam and tighten the clamp screw and check the action. The throttle butterfly should just begin to open as the roller passes center of the two marks on the cam.
 
kimcrwbr1 said:
Have you checked engine sync between throttle opening and spark advance? On your engine there are two marks on the throttle cam, line the follower roller center of the two marks and loosen the clamp screw for the throttle shaft on the carb. hold the roller up tight to the cam and tighten the clamp screw and check the action. The throttle butterfly should just begin to open as the roller passes center of the two marks on the cam.
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Checked the linkages previously.All good there.thanks
 
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