Mercury 4hp outboard. 1992 vintage unused past 2 years. now has a problem with the water cooling telltale.?

Question

After running for a few minutes water from telltail reduces to a few drips. the pump impeller is good. Blowing air up the telltail outlet clears it for a few more minutes, then it stops again. Its probably some scale blocking the outlet. Question: how do I flush it out ?

Answer 1

I would defiantly change the impeller.  When you change it make sure there are no pieces of the old one floating around in the intake passages.  Does the engine run hot?  When you have the lower unit off blow through the tube tube with compressed air.

Answer 2

vinegar disolves scale.

Answer 3

I suggest changing the impellor anyway.  After a 2 year lay-up, the impellor rubber is going to be hard and have lost most of its good properties anyway.

  As for the telltale, run it in some warm water, and try clearing the tell tale with a decent size needle from the outside.  The blockage will probably be close to the tell tale hole.