Re: 1978 7.5HP Johnson/water pump removal
Hi John,<br /> Always post your motor's model and serial along with your question, as there was no 7.5hp model in 1978. <br /> I will operate under the assumption that it is an early 1980s model, in which case it is not uncommon for the driveshafts to become one with the crankshafts on those motors. For some reason, either the grease used in the splines was of poor quality, or people forget to install new o-rings when servicing the pump impeller, or maybe a poor crankshaft alloy, but whatever the cause, the result is the same. It's possible to pull the gearcase off and leave the driveshaft in place by forcing the waterpump drive key past the pump housing. <br /> You can then work on extricating the driveshaft from the crankshaft. I prefer to remove the powerhead from the exhaust housing, bringing the driveshaft with it. I can then use a pair of ViceGrips to clamp onto the driveshaft, which gives me something to hit with a hammer. Lots of penetrating oil helps, too.<br /> The reason I prefer to remove the powerhead is that once the driveshaft is removed, I can now inspect the splines in the crankshaft - which, if you've gotten this far, are often rusted out.<br /> If you're lucky and the driveshaft comes out with minimal effort, and the splines are okay, then reassemble with new impeller, good waterproof grease on the upper shaft splines, and a new o-ring in the groove at the top...<br /><br />- Scott
