Merc 5.7 1992 Knocking

[drumnfishrman1]

Just purchased a used Wellcraft with a 5.7 Merc. When at idle there is knocking coming from the engine, throttle it up and it goes away. Engine runs very strong and smooth. Took it back to the dealer and was told it's the exhaust baffles. When I got a second opinion I was told it was water in the cylinders most likely. I'd like to get it resolved before I get past my 30 days.
Both seem to make sense, being a non-mechanic.

Anyone have an easy way to determine the correct diagnosis? I will most likely take it back to the dealer to investigate further. I would like to feel confident that they are correct. Any help is greatly appreciated.
Thanks!

 

[Bondo]

Re: Merc 5.7 1992 Knocking

Took it back to the dealer and was told it's the exhaust baffles.

Ayuh,... If they're Knockin',... They need replacing...
Have the manifolds,+ risers Checked at the same time... Then you'll have Both answers...

 

[cr2k]

Re: Merc 5.7 1992 Knocking

Pull the spark plugs and turn it over, if water comes out there ya go. If not probably the flappers.