Good idea to only use non oxy fuel. Ethanol will damage seals, hoses and diaphragms. Ha....to ME thats a NEW motor. I make 'em last. My everyday fishing motors are 70's stuff. Make sure the water pump is fresh and buy a high quality impeller. When you couple up the lower unit make sure the water tube enters properly the grommet. I recommend Amsoil pre-mix 2-stroke oil for that motor as I have several 25 horsepower Mercs just like yours. I've been using Amsoil pre-mix 2-stroke for 50 years now. Mix 100 to one in full needle bearing motors such as yours and 64 to 1 in semi needle bearing motors, more common with early OMC's. The early 9.5's Johnson and Evinrudes can run with 100:1, however....as they incorporated full needle bearing crankshafts. Too much oil, and paired with "rubber eating" ethanol can cause motor mount failure. Im repairing a 9.9 hp right now. Keep fishing line off the prop shaft in order to protect knocking out the seal. Water contamination has destroyed many....especially the early Mercs w/o stainless steel driveshafts. Its getting hard to find good shafts now for the early Mercs....even here in freshwater lake country.... Northern Minnesota.
