Re: Johnson Sea Horse 4HP
If you're uncertain of the motor's service history, one thing I would do before you use it too much would be to replace the water pump impeller. They can dry out and rot with age and a new one is cheap insurance. They can be had at an OMC dealer, or even NAPA for under $15.00 and take about 15 minutes to replace. The impeller is located in the bulge between the gearfoot and the mid-section. Remove the lower unit (four bolts and drop it from the motor. Remove the o-ring at the top of the driveshaft. Remove the two screws on top of the impeller housing and HOLDING DOWN on the driveshaft, pull up the impeller housing and impeller. If you pull the driveshaft out, it can be a pain to put it back in as the pinion gear may shift. Keep track of the drive pin/key. Clean up the impeller base plate with a solvent (I use lacquer thinner) and the base of the impeller housing. Install the new impeller and reverse the procedure. Make sure to grease the top of the driveshaft spines and replace the o-ring in its groove. It'll take a little finesse, but the hardest part of the whole procedure is usally lining the splines back up into the driveshaft. <br />Have fun!<br />- Scott