Bronze-bushed powerhead bearings

[TN-25]

Hello all. I am considering the purchase of a 1958 Johnson AD-12 7.5 horse motor. I am told it runs well. After learning about the dangers of getting a motor with excessive crank to main bearing clearance I am curious on how to check for such issues without tearing into it. Do I look for a motor than can idle right down smoothly? A seller could always say it needs a tune-up but he may not even know that the bearings have excessive clearance.

My 1950 Johnson TN 5-horse's restoration is nearly complete, but it took another block & crank to get the desired clearance.

Has anyone here dealt with the clearance issues relating to the old bronze-bushed non-replaceable main bearing motors? Is hard chroming the crank journals and turning them down to the correct diameter for tight clearance with the bushings a realistic option?

Thanks for any input.

 

[JCF350]

Re: Bronze-bushed powerhead bearings

Clean the crank journals up and knurl the bushings.
Ain't really a fix but it'll extend the life some.