F25 water in oil

[seacraft 23]

I have a 2000 f25 4-stroke that is getting water into the oil. It is getting into the lower cylinder and vapor locking the engine. I replaced the head gasket and the engine ran fine for a day and then did the same thing. Valves looked good when the head was off, with no sign of damage. I am doing a leak-down test tomarrow, any other things I should look at? Can water come from a bad exhaust valve?

Thanks

[boats.net]

Check to see if motor sits too low in water, the exhaust releif holes on back of mid housing should be at leat 4-5 inches above the water line.

[DeltaDawg]

I have an F25 too and while reading my Yami manual I noticed a service point that one should measure cylinder head warpage accross all areas (of the mating surface with the block) for a warpage limit of 0.1mm (0.004in). If it is out of specification resurface or replace the cylinder head. Then there is a picture of placing the cylinder head on 400-600 grit wet sandpaper on the surface plate and resurface the cylinder head using a figure-8 sanding pattern and rotating it several times.