Tuning My Johnston 4hp

pete145

Recruit
Joined
Jun 19, 2012
Messages
5
hello guys, I have a Johnston 4hp 4W79D and it is running hot. I took apart the pump and it is fine, however I noticed in the top of the pump housing there is a small hole that allows water to escape out. Is this supposed to be there? As a relief hole maybe? or is it something someone drilled for who knows what reason? Thanks for your help.
Also, how should the needle valve on the carb be set (how many turns) and what is the best gas mixture? Thanks again.
 
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