Newley rebuilt 351w - getting water in intake?

[Oleeolson]

Just finished a rebuild on a 1985 351w had it running seemed perfect, as time went on started breaking down and got worse and worse. Pulled the plugs and discovered they all had water on them? Can't figure where it would be coming from? Will do a compression test on it tonight but don't believe it will be head gaskets - both sides after that I guess I'll pull the intake and see what I can find?
Could a wrong gasket or something cause this?

[Oleeolson]

Know I'm thinking back - the boat back fired and seemed like it reverse rotated for a second or 2, blew fuel out the carb
wondering if it sucked in water then? Wouldn't explain why it was running so bad but could explain the water.

[Sell]

Check the exhaust manifolds & risers for corrosion.

[TRDon]

A poorly seated intake manifold would also leak water into the intake tract