Reply To: Johnson RDSL-21 mercury Switches

[Tom Alexander]

Mumbles: thanks for the thoughts. I completely rebuilt the gearcase as it was very rough when I turned the prop by hand when I got the boat and engine. I found that the pinion gear shaft bearing surface and it’s bearing was badly corroded probably due to the seal below the impeller failing.  The drive shaft was badly worn at the seal contact point just below the water pump. I tried to fix with a seedy sleeve but the sleeve would not go over the splined end of the shaft and not take the ‘shape’ of the splines, so I located a new/old shaft that was in very good shape. It has a tapered area narrowing toward the top so we will see if it is up to the task. But to the point you made I did replace the impeller and the pump ‘body’ too at time in rebuild. The impeller did not look at all like the one in you photos though. On Diesel engines I have had the pump folks had impellers that could handle a bit of dry running. I think they were blue in color. I could fine nothing like that in the outboard motor pump information I researched. Any info in that regard?  Thanks again. Tom