1969 4hp Johnson OVERHEATS/New Impeller

[Larrygs]

My Johnson outboard is still overheating even though I've installed a new impeller (and the old one looked in good condition). I have two questions I need help on...
1) At what location is the cooling water expelled on this outboard? I thought it came out at the 8 toothpick sized exhaust holes about halfway up from the bottom but only a VERY light spray blows out there.
2) After pulling off the bottom again, I have put both suction and air pressure at the end of the 1/4" copper water uptake tube just above the impeller housing thinking it may be stopped up. When I use the air pressure, I can not feel any air outgo anywhere! Does this mean a blockage and where do I go from here? Thanks...Larry

 

[Vic.S]

Re: 1969 4hp Johnson OVERHEATS/New Impeller

most of the cooling water leaves with the exhaust under water.

You should see a spray or mist from the relief ports on the leg but there is no telltale AFAIK

Put a water hose on that water tube and you should be able to force a water flow through the engine. If you cannot its blocked, scaled up probably

Not sure if the side cover gives access to any of the cooling system like it does on slightly larger engines.

The passages round the cylinder head are vulnerable to blockage with scale and corrosion