I recently bought a 1985 Renken with a GM 350 and an OMC drive. When I brought the boat home, I knew it had BAD batteries. So I bought 2 new right away. I installed them, hooked up the "earmuffs", turned on the hose, and tried to start the engine (notice the sequence). When I turned the key, the starter "thumped" into the flywheel, but would not turn it over at all. After reading some other threads, I pulled the spark plugs. When I got to plugs 1 and 7, water actually poured out of their holes. Is there any chance, with high hose pressure, that I pushed water back through the manifold and into the cylinders, or would this sound more like a head gasket or manifold leak? Hopefully it was user error and I just need to let them dry out and maybe use a plastic tub next time instead of the muffs? Please hurry, I'm scheduled to go on a vacation and I'd LOVE to take a working boat.