Reply To: Johnson S45 – Stuck – Which Piston to tap?

[George Emmanuel]

OK, so everyone is assuming the pistons are stuck. That may not be the case. The S-45 has a bunch of places where corrosion could prevent the motor from turning.

First, remove the lower unit. Simple removal of 3 nuts and it should drop down. If the motor doesn’t turn and the propeller turns, that’s not it. Re-install the lower unit.
Next remove the rotary valve on the front of the engine. Make sure you index the position of the gear when you remove it so you can install it as it was. If the motor doesn’t turn and the gear does, check the index of the gear and replace it.
Since you’ve already, (at least I think you did), used penetrating oil in the cylinders, it could be the crankshaft is stuck. If the pistons are covering the exhaust ports (you can tell by removing the muffler) lay the engine on its back and fill the crankcase with 50:1 mix and let it soak. It will slowly work its way into the upper and lower mains—may take a couple of days. (Keep the engine away from everything for fire safety).
If the pistons are not covering the exhaust ports, turn the engine upside down (resting on the flywheel) and fill the crankcase with 50:1. Wait till you see it leak through the upper main. Then turn the engine upright and again fill the crankcase with 50:1 and wait till it leaks through the bottom main. This way you will know that the mains are lubricated. Then carefully use the strap wrench and see if the flywheel will move. Perseverance pays off!