1973 Johnson 65hp, water in cylinders

[strongcones]

This one is frustrating.
I had the motor overhauled five years ago, and it had been working well up till late last season, when heading back to the launch there was a very noticeable loss of power. I poked around a little, but didn't have the time to spare, so I stored it. Now that spring is here, I got some gumption to work on it again. I put the earmuffs on it and tried to start it up, but it was bogging so hard, I figured there must be water in the motor. I pulled the plugs, and sure enough, LOTS of water came pouring out of the bottom cylinder's spark plug hole.
My first thought was the head gasket, so I took the head off, surfaced the head, water jacket, and thermostat cover, got new gaskets, and put the assembly back together. Then I put the muffs back on a ran some water through the system, and it looked fine.
When I tried to start the engine, the same bogging thing happened and sure enough, still water in the bottom cylinder.
I've checked everything I can without removing the power head, and everything I see looks good.
So I'm wondering what the next most likely reason for this problem is. I have the Johnson shop manual for my motor, and from the diagrams it looks like the exhaust gaskets could cause this problem. What do you think?

[RUSTY63]

On that motor I would be looking at the exhaust plate gaskets.

[strongcones]

And to get at them, it looks like I have to take the power head off, right?

[Sportwin]

You did take a fuel sample from the fuel tank to make sure the water isn't coming from the fuel tank didn't you?

[strongcones]

It was in fact the exhaust plate gaskets.
I started unbolting the assembly, and I had to drill two holes in the lower motor housing to get at two of the bolts, but it came off. I found an obviously blown-out section of gasket where water would be streaming into the manifold. Got the gaskets ordered, and they should be here Monday.
Thanks RUSTY63!!!