150 Johnson rod bearings snapping

jc turtle

Seaman
Joined
Jul 23, 2011
Messages
67
When I tighten the rod bearings to 20 lbs and turn the crank,
The bearings make a snapping sound when I turn the crank.
I have tried aligning the caps many times with the same result.
If the bolts are finger tight there is no snap. Any ideas. It ran
With no noise,
But had low compression that’s why I am rebuilding it.
Thank you, John
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
7,985
Did you make sure the caps stayed with the correct rods? Otherwise wrong bearings?
 

jc turtle

Seaman
Joined
Jul 23, 2011
Messages
67
I was careful keeping them together but a few did get mixed up. I should have taken better care of them. Must I replace the snapping ones with new bearings? Thank you, john
 

tphoyt

Master Chief Petty Officer
Joined
Jun 10, 2010
Messages
899
Oh boy!
Rods caps and bearings should have stayed together and been put back on the same journal. Even with new bearings you could have binding on the crank if it’s a high hour motor and if the caps are miss matched to the rods it could compound that even more. Caps and rods are machined together and need to stay that way. In a perfect world you would have the caps and rods matched with a mic the best they can be and have the cranked turned and put in new undersized bearings.
Just my opinion though.
Best
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,035
Sometimes rod caps have match marks with the connecting rods. Usually a scribed line. You might see if you have those.

Obviously the bearings, if installed correctly and serviceable, will have zero clearance.

A lot of motors call for new rod screws, after rebuild. Does your motor need these?
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
7,985
What is the model # of your motor? My guess is you did not keep the caps and rods together. Since they are broken caps they are pair, rods and caps stay together. The bearings should interchange between rods , not the best practice but it will work. Does your motor have Crank rings? Are they in correctly? Bearing locating pins in correctly? You will now be replacing at least 2 rods because by torqueing the wrong cap and rod together you ruined those. Go through the rest of your rods and make sure the caps are on the right rod.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,033
It should not be hard to find which cap belongs with which rod !!----And you have to get this correct.-----These rods are FRACTURED when they are made and the cap will only fit on one rod.-----No point starting this motor if rods are not matched.
 
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