Johnson 150 overheat left head

[work2hard]

1989 150 one year on rebuild. Temp gauges both heads. at just above idle in gear 200 left, 140 right. cant hold hand to left head. Verified with infra-red. pulled t-stats, same. strong stream from ind tube. pulled ststs and housings, started and ran. good water flow out stat opening on right head. Almost none on left, same at all speeds.<br />What is the water path from pump through engine?<br />Any ideas?

 

[Joe Reeves]

Re: Johnson 150 overheat left head

There are water deflectors between the top and center cylinder, center and bottom cylinder, and between the bottom cylinder and the block.<br /><br />The deflectors are in reality a short piece of rubber hose that directs the path of water. The deflectors between the cylinders do at times swell sideways, towards the block wall, resulting in a water restriction. I suspect that this is your problem.<br /><br />Unfortunately you must remove the cylinder head to inspect those deflectors.