Water in exhaust manifolds

[Lou C]

I see some light scuffing on the cyl wall in the 1st pic, definitely a valve seal leak in one cyl, also the motor was rebuilt at some point because I see a piston stamped .030”.
Looks like some very light corrosion in one of the pix as well. Nothing too bad though….

 

[Scott Danforth]

Holy detonation pock marks batman.

Agree with Lou. Someone has been in the motor before

 

[chartersj]

I see some light scuffing on the cyl wall in the 1st pic, definitely a valve seal leak in one cyl, also the motor was rebuilt at some point because I see a piston stamped .030”.
Looks like some very light corrosion in one of the pix as well. Nothing too bad though….

Yeah I bought the boat with roughly 100 hours on a rebuild. I’ve since put another 100 on it. To me it didn’t look like water had been running though it too much if any. A week before I initially pulled the risers I did leave the boat in salt water for a week. Which I normally don’t do. I would think if salt had been laying around I would have seen more traces of rust

 

[chartersj]

Holy detonation pock marks batman.

Agree with Lou. Someone has been in the motor before

What would be the reasoning for detonation?

 

[Lou C]

If you blow up the pix of the top of the pistons you can see pock marks, that is what I think Scott is referring to. Can be Caused by lean fuel mix, fuel octane too low, timing too advanced and prop too large in pitch. If the engine doesn’t reach its specified wide open throttle RPM you can get detonation because the engine labors every time the boat gets up on plane. What your max WOT RPM? Should be about 4400-4600 rpm and actually higher is better as long as it’s under 5,000 rpm. Check your timing make sure it’s right. I use at least 89 octane gas no matter what the manufacturer says about using regular. That’s a big heavy boat for a 5.7. What size prop is on it now?

 

[Scott Danforth]

What would be the reasoning for detonation?

Lou has the list of detonation causes above