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

 

[Lou C]

I am going to post up an old pic of my 4.3 when I had it apart about 10 years ago. The pistons show carbon build up (the Q-Jet was running too rich then for sure) and on the center piston you can see the lack of pock marks, this engine at that point probably had at least 1500 hrs on it, had one bad overheat and the blown head gaskets a few years later, but it doesn't seem to show detonation damage, at least from what I could see. The liquid in the cyls is fogging oil to keep the cyls from rusting. Block still needed some cleaning in that pic!
Maybe the water in your manifolds was a blessing in disguise, if not looking for things you'd probably never had noticed that.
I would: consider getting the injectors for your TBI system cleaned, make sure fuel pressure is what it should be
check timing
see what your WOT max RPM is, if too low you have to start looking for causes, sometimes it's as simple as the boat ran OK with the wrong prop on it and no one ever thought to check, on mine it had a 14.5x19 which was too much pitch, it needed a 15x17 given the little 4.3 and the weight of the boat (a lot for a 20')
Another cause which could be easy to miss, is the ratio of the outdrive, each engine has it own specific outdrive gear ratio like a ring and pinion on a tow vehicle. If the outdrive was replaced, someone could have used one with too tall of a gear ratio, so that can be a cause too.
use at least mid range fuel, in a marine engine you really can't hear pinging or detonation but it will eventually burn valves and can shorten engine life.

 

[chartersj]

I am going to post up an old pic of my 4.3 when I had it apart about 10 years ago. The pistons show carbon build up (the Q-Jet was running too rich then for sure) and on the center piston you can see the lack of pock marks, this engine at that point probably had at least 1500 hrs on it, had one bad overheat and the blown head gaskets a few years later, but it doesn't seem to show detonation damage, at least from what I could see. The liquid in the cyls is fogging oil to keep the cyls from rusting. Block still needed some cleaning in that pic!
Maybe the water in your manifolds was a blessing in disguise, if not looking for things you'd probably never had noticed that.
I would: consider getting the injectors for your TBI system cleaned, make sure fuel pressure is what it should be
check timing
see what your WOT max RPM is, if too low you have to start looking for causes, sometimes it's as simple as the boat ran OK with the wrong prop on it and no one ever thought to check, on mine it had a 14.5x19 which was too much pitch, it needed a 15x17 given the little 4.3 and the weight of the boat (a lot for a 20')
Another cause which could be easy to miss, is the ratio of the outdrive, each engine has it own specific outdrive gear ratio like a ring and pinion on a tow vehicle. If the outdrive was replaced, someone could have used one with too tall of a gear ratio, so that can be a cause too.
use at least mid range fuel, in a marine engine you really can't hear pinging or detonation but it will eventually burn valves and can shorten engine life.
View attachment 420508

Wow you’ve been very helpful on here.
Very much appreciated.
The 5.7 was the smaller engine for this boat for sure, but with the bravo 3 drive and 22 pitch props it doesn’t struggle to get on plane. As far as top end rpm. I think I’m around 4500. But I’d have to double check that, probably next summer as it’s getting cold here in Canada. I do have a fuel pressure kit to check that, and I agreed about getting the fuel injector cleaned over the winter.
I have my new gaskets so I’m going to put the exhaust back on, swap the plugs around, and keep the throttle up a little more to see if that helps with the water in the exhaust. I looked down through the y pipe for broken off exhaust flappers that might have failed at one point but didn’t see anything.
I’d love to think I could see 1500 hours on this one lol
As far as I know it’s the original drive to the boat, that was re-sealed same time the engine was rebuilt.

 

[chartersj]

I have plugs in the top of my risers big enough for my borescope to fit in as well

 

[Lou C]

I have plugs in the top of my risers big enough for my borescope to fit in as well

seeing as how you're in fresh water now, that exhaust should last the life of boat, hopefully you can stop any leaks.
the one thing we still don't know, is if the water was caused by condensation or a leak, but if you can check em as I did, if you see a bit of water after idling on the water hose but not when the boat was run fast enough to get the exhaust up to temp, then I'd say it was condensation. If you still get water after running it enough to get it hot, then it's a leak.
I think 1500 hrs is entirely possible, as long as maintenance is kept up and you use good fuel, and monitor things like max RPM (4500 sounds like it's high enough) and timing. Marine engines especially inboards are under loads that you do not see in automotive applications, where you have a multispeed transmission and aren't pushing a wall of water out of the way to get the boat up on plane.