5.7L Mercruiser water in #5 piston

[EKM]

Working on my friends boat and engine will not start. Pulled all the plugs and #5 is spitting out water. Riser were replaced 2 years ago but not manifolds. Its a 2000 Sundeck 22'.
How can you tell if its the manifolds or rotted heads? Does a bad manifold leak into 5 or cyl 7?
Thanks for any tips.

 

[Mr Mac]

It could be a blown head gasket. It is a pain in the butt, but I would pop it off and investigate.

 

[scoflaw]

Pressure test the water system first before you take anything apart. The manifold can also be tested with acetone

 

[Wanderer 290]

Water in #’s 3,5,4 and/or 6 are indicative of water intrusion in the exhaust system but there is always the possibility of another problem.
If it is the exhaust system it could be a cracked manifold, riser and /or elbows or a gasket failure at their respective joints. Rent the video scope from AutoZone and open the exhaust system where the elbows join the y pipe and take a look inside. The answer will be revealed.
The video scope is also small enough to insert into the spark plug hole for further investigation.

 

[Bt Doctur]

water can also run up the exaust if he stopped suddenly and just turned the key off. if it dieseled it would do the same