Reassembling the 2000 Yamaha f100 four stroke outboard. All I did was replace the crankshaft main journal bearings and a head gasket that was blown. I bought it from someone who ran the engine for 3 months after a shop rebuilt it. The guy said it overheated and had locked up. I bought it and opened it up to see what she looked like inside. Head gasket was blown and main bearing were toast. Everything else looked fine, kinda!