Inliners International Forums General Discussion Engines Fired up the rebuilt engine for the first time

And there is such a thing as too high a viscosity in an engine. The 60w is very likely too high. I think it would be a good idea to go back to 30w. Try the 5w20 if you like but you should not need 60w in a brand new engine. You have tight clearances and running heavy oil isn't helping circulation. And do cut the filter open and check it.