Reply To: Johnson RDSL-21 mercury Switches

[Don]

Tom Alexander wrote:

Lindy 46: Good eyes! Thanks for that. You are right and for subsequent runs I did raise the water level. For this first run I did have a pressure water (Municipal water supply) source feeding into a screwed on plate on the intake to make sure I had water into the supply side of pump. While I don’t think this ‘proves’ a water pump is working sufficiently on its own, for the  first approx 10 minutes of running I did keep the hose pressured up and connected just for my peace of mind. Then I disconnected and the pump has proved since to be working well.

Thanks  Tom Alexander

Yes, using that water supply adapter can surely mask a bad water pump.  There is no need to use it when the engine is being run in a bucket.  You go on to say the water pump is working just fine, how did you determine this?

This engine looks to be in beautiful original condition, perhaps someone repainted it.  You do want to be very sure that the cooling system is working properly before using the boat/engine out on the water.  Overheating at high speeds causes damage very quickly.