Re: Looking for parts diagram for Johnson 10hp 1960
Ok, first are you sure you're looking at gear oil all over the top of the lower unit, and not just unburnt oil from the exhaust? If so, clean up the inside as best you can and look carefully for any sort of crack in the lower unit casing itself. If you don't see anything suspicious, re-install the driveshaft and find a way to pressurize the lower unit before you pull it apart. If it is unburnt oil, 9 times out of 10 the leak is at the gearcase fill and drain screw gaskets, so just replace them and see if the leak goes away.<br />Disassembling and reassembling these split lower units is really easy compared to modern gear cases. You'll see if you have yours apart how simple they really are. The only problem people seem to run into is removing the gearcase cap screws themselves. If they weren't sealed with sealant, you'll need an impact screwdriver and possibly some heat to get them out.<br />When you pressuize the lower unit, go easy on it. I remeber reading somewhere not to go beyond about 5 psi with these single-seal gearcases. A bicycle pump with a carved tire valve stem or a syringe and tubing work well, and a kiddie pool or a bathtub make good test tanks for finding bubbles. If you use a bathtub, be certain to clean the gear oil ring around it after you drain the water to cover your tracks!<br />Once you know exactly where the leak is then fix it. If it is the shift shaft seal, you'll need to disassemble the gearcase to get the shift rod out of your way. It comes out on that side only.<br /><br />Tell us what you find!<br /><br />PS - for a impeller to look brand new, it's vanes should stick out straight like a star. If they are curved at all, the impeller has taken a set and must be replaced.
