4 clyinder 40 hp merc 1993, Water on bottom cylinder spark plug

Water in bottom cylinder of my 40 hp early 90's Mercury 4 cylinder outboard serial # OD229057. What could be the problem? I thought it my be a head gasket but was told there my not be any head gasket on this type motor, don't know if its true or not! If there is no head gasket could it be a cracked water jacket or cyclinder? There is 105 psi in all the other cylinders and 100 psi in the bottom cylinder where the water is occuring. The engin runs on 4 cylinders untill the water intrusion stops the bottom cylinder then the engine only runs on 3 cylinders. Please help if you can!! regards!

Gary,

You have one of two problems, The first if YOU are lucky is the inner exhaust baffle plate is leaking into the ports or the bottom crankseal is toast and sucking it up on the bottom cylinder. Those are both OK price wise to repair about 4 hours labour and 50$ worth of parts or 150$ if you need a new baffle plate. The other is a porous cylinder which is not very common on #4 usually it is number two. The first two repairs can be done by just lifting the powerhead off the midsection the latter requires a replacement block. I pressure test the block with a pressure plate on town water pressure while heating the end of the cylinder with a propane torch and hot water, that is the only way you will ever see the leak.

Dave

Thanks Dave!! You are a true Hero! May many blessings and good fortune come your way friend!