20hp opposed twin

I bought a Murray wide body for 50 buck at flea market it's got a 20hp oppy on it. It runs but smokes and has a light rattle. Is motor worth rebuilding or just install a 15.5 ohv that i laying around

All depends on what you want to do with it I guess. But, it's probably cheapest to just run it the way it is.

I don't know a whole lot about oppy twins.... But if I were you I would just run it the way it is... And wait till it blows... Or smokes so much... You think it's on fire... Then rebuild it

rebuilding, in the engine world isnt to much, but mower wise, its upwards of $150, kinda expensive, plus you need the right tools, torque wrench, hone, assemboly lube, thread lock, engine oil, ect. I think the 15.5 would be a great motor by itself, and id part out the 20hp on ebay. You'll come out on top from what you paid for. just me. Is it pressure lube (oil filter on side) by chance?

No oil filter. I think ill part it out and just run the 15.5. It doesn't seem worth $150 rebuild. Thanks for the info