Water in 43l cylinder

"I have a 1996 4.3l V6 mercrui

"I have a 1996 4.3l V6 mercruiser. The engine was hydrolocked. Cynlinder 1 was full of water. Here's when it happened: I ran the boat (salt water), trailered it home, flushed the engine with fresh water, and parked it in the driveway. The next time I tried to start it, it was hydrolocked. Here's what I know: When I flush the engine, I use a hose and mouse ears. When the flush is finished, I turn off the engine, then walk over to turn off the hose (water pressure stays on the engine for about 1 minute). Cylinder 1 was full of water, and the other 5 cylinders had some moisture (rusty plug and small amounts of water). Compression in all cylinders is good (140-180 psi). The risers are 1 yr old. Cylinder 4-6 exhaust manifold is 1 year old. Cylinder 1-3 exhaust manifold is 5 years old. Cylinder 4-6 head was rebuild 2 years ago.

Any advice? I'm thinking the exhaust manifold is bad. But, I'm concerned that maybe the intake gasket is bad."

Most likely the manifold at #1

Most likely the manifold at #1 is leaking.You can remove the riser and inspect that for holes or damage then CAREFULLY fill the ex manifold with water up to the riser gasket and look inside the exaust section to see if any wetness appears.
just had a 2 year old motor with the same symptoms. the odd cylinders would hydro lock. after filling the manifold i had to wait 3 minutes for water to appear inside the manifold..

"[b]"I'm thinking the

""I'm thinking the exhaust manifold is bad."

Ayuh,...

I'm finding it hard to believe you change them 1 at a time, rather than as Pairs...."

I don't understand why I s

I don't understand why I see signs of water in all cylinders if the exhaust manifold on 1 side is bad.

salt water is getting in the o

salt water is getting in the oil!!!!!!!!!!!

could it be the intake manifol

could it be the intake manifold?

you shouldnt hydro 1 cylinder

you shouldnt hydro 1 cylinder only with a crack.
cracked intake is more likely to flood the whole motor internally not in a cylinder.you`d be surprised how much water can get in a motor with only a broken valve spring. hydro from just sitting in one bank is a sign of a leaky exaust manifold or a leaky riser.