[SPORTJET]

New to site & trying to work on my own engine. Have 175HP SPORTJET combo, thru a rod! Was given another engine to swap, but it was very tight! Would hit & then sieze, wait a few minutes would turn over & hit again. Was told it was top main bearing. Took the bearing out of the motor that had broke rod & put it in the "good used motor". It now runs for aprox 10-20 seconds & does the same thing. Old bearing deffinatly looked bad & the used 1 I put looked much better, but not sure, being I have never seen a new 1 before. Anyway, my question is, should I just go ahead & replace all the main bearings or maybe just this top 1? What little info I got locally say these motors are very bad about loosing this top bearing only? Any & all help will be greatly appriciated.
Thanks to all who respond.

[MikeW]

Take time to do it right the first time! Replace all the bearings.