1978 Johnson 175, 200, 235 HP Outboard Service Manual, Page 71Get this manual
Hold 125 (52 C) and 163 (73C) Thermomelt Stik on top of each cylinder head with engine first running 700-1000 R.P.Mand then 3000-4000 R.P.Min forwardIf 125F (52C) Thermomelt Stik melts and 163 (73 C) Thermomelt Stik does not, then thermostat is functioning properlyIf both melt then engine is running too hotIf neither melt, then engine is running too coldSee Figure 5-9 INSPECTING CYLINDER WALLS AND PISTONS
aDisconnect coil orange leads at each power pack terminals 1, and 3bSlide back heat switch insulating sleeves and disconnect leadscDisconnect spark plug leadsdRemove 14 screws from each cylinder headTap cylinder head with mallet to break the gasket seal and remove cylinder heads and gasketsDo not remove water deflectors in cylinder water passages unless deterioratedSee Figures 5-10 and 5-11The deflectors direct water circulation and are shorter in depth than the passage to allow water to drainIT replacement is necessary, order part number 322411Failure to use the proper replacement part could result in engine damage through overheating