cylinders stop working once boat in water

[Litopcas]

Hello,

I have a 1990 johnson 140hp engine, when on shore with a water hose connected it works fine, however once the boat is put into water 2 cylinders seem to stop working. Compression in the cylinders is 8.
Any input would he appreciated.

Also does anyone know a mechanic for these engines in south east England?

Many thanks,

V

[Joe Reeves]

What does that mean.... compression is 8??? Compression should be up around 100 PSI and fairly even on all cylinders.

Standing in back of the engine facing the spark plugs, the cylinders are marked as follows. What are the psi readings of all cylinders?

2....1
4....3

With "all" spark plugs removed, the spark should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?

Which two cylinders seem to stop working?

I assume you're saying that when in the water, you can remove the spark plug wires from those 2 cylinders and there would be no difference in how the engine is running.... is this correct?

Has anyone been working on the engine, and if so, what has been done so far?