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175 johnson vibration

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richarda

New member
i have recently purchased a 19

i have recently purchased a 1996 175hp johnson
and it seems to have a vibration problem from 1500rpm all the way to 5000rpm the dealer has sent out the crank and it came back ok it has been tested with bottom end off still the same
does anyone have any other ideas i am stumped it will eventually vibrate the rivets out of the boat any help would be appreciated thanks richard
 
"In assuming that you've a

"In assuming that you've already tried another propeller.......

Remove the propeller. Attach a large screwdriver or some object of your choosing to some portion of the lower unit so that a point of that screwdriver/object is dead center with the center of the propshaft. Now, slowly turn the propshaft by hand to see if it is bent. Don't try to sight the bend simply by eye by spinning the prop as some bends are so slight that the screwdriver/object scenario is required.

Check the propshaft for vertical play (bearing wear).

With the hood off and the engine running at the speed where the problem exists, have someone view the flywheel to see if it is staying true OR if it is actually flexing.

If water has been entering the lower unit, it may be possible that the driveshaft top bearing/seal assembly has failed which might result in viberation. I've never encountered this (excessive wear/viberation) but I would think it possible."
 
"Providing all rubber elements

"Providing all rubber elements are in good shape, it might be either a failing cylinder or has someone changed a piston or more from original? (different weights?)
If a mechanical 'misalignment' there should be some wear in crank shaft bearing races to indicate?
(have once had a similar incident once where someone replaced a crank case from another engine!)
No dislocated/missing magnets in fly wheel?"
 
"i,..have rebuilt eng's,..

"i,..have rebuilt eng's,..w/diff size pistons....and,by the book,that is perfectly fine,but never had a bad vibration prob...
in 31 yrs,..i have found,that if an eng needs an overhaul,..do them all the same...
at my shop,...for better or worse,..we do an overhaul all,..--,030 over.
now,..this has ALWAYS....provided an even engine,that idles fine,and the balance,i feel,is better off for longevity,....
but,...i am an extreme perfectionist,when it comes to my customers.I have always,had the attitude,that if one needs to be 30 over,take them all....and the only comebacks i have had,...have been ignition related.....(bad pack,bad batt cables(hard starting) that worked fine for us but 3 mos ltr,was not up to 'par'
in thge 80's,i had some wtr imp fail,(sierra),..they paid,for any damages.I have the ultimate respect,for sierra products nowdays.
however,...........since i said that,..the only prob we have had ,in the last2 yrs has been w/fuel conn's..diff gto connect.
I do agree,that the OEM,...is ALWAYS...BEST..
I HAVE USED WISECO,SIERRA,pistons,and both perform well.
in the 80's I would not do an overhaul,w/out OEM pistons...
since then,we have ventured out and used the 2 w/good results....
I have found,whichever pistons,one chooses,..do them all the same....thats what we do,and it wks well,w/of course,lgr jets etc."
 
"as far,as your vibration prob

"as far,as your vibration prob,..i feel it is going to be lower unit related/prop related.u could have a bad pwrhd,but where the "rubber meets the road"......is down there."
 
"then,..an educated guess...wo

"then,..an educated guess...would be a bad upper or lower bearing,..or a rod,that the cap has backed out on..now,the first scenario,...is highly likely...
at this point,..i would tear it down to investigate...
however...........be ready w/deep pockets,to do a thorough,rebuild....dont just fix the obvious,if u go this far,rebuild it.....back seat thinking...we;ve gone this far,get it done!!
overhaul time!"
 
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