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Not sure on the age of them. I’m thinking I’ll change the risers first in the spring and see how it is after that before I do manifolds too. I filled the manifolds with water but not acetone so I will try that too. And yeah the plugs do seem like it’s running rich. I still plan to have the...

The boat is now winterized for the season

So I swapped the plugs around, filed the mating surfaces down on the manifolds and risers, and run it again on the hose. First I left the hoses to both exhaust manifolds off so no water was going through the exhaust, and let it run only for 30 seconds. Put my borescope in through a plug hole in...

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

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...

What would be the reasoning for detonation?

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...

Good idea about the oil analysis. I do usually cut my oil filters open to have a look. I got my borescope today. Nothing really sticks out to me. All the pistons and cylinders looked similar to my untrained eyes. And doesn’t really appear to have any rust streaking in the exhaust ports. I’m...

Well I can’t say for sure as I didn’t keep track when I pulled the old plugs. I’m thinking of swapping the steam cleaned plugs with the normal looking plugs and see if the results follow. I’ve order more gaskets,,

No water in the oil. And Ive never got any water out of the cylinders. Just a little laying in the bottom of the manifolds. I’m wondering they don’t leak until they heat up

Unfortunately I didn’t keep track when I took the original ones out. I put new ac delco ones in. So am I looking at something deeper then exhaust?

Another picture of the worst looking ones

It’s efi but throttle body injection. So it has two fuel injectors not 8. On a couple of the original plugs I half wondered if I was seeing a little rust color on them. I’ll attach a picture. They were in hard and the ones that broke were from me taking them out.

Yeah they are surprisingly heavy. I got the exhaust from my buddy, but not sure they are usable. The mating surfaces are worse than mine. The only thing I’m confused about is the difference in the spark plugs with the condensation theory

My engine has the cold manifolds. Only one hose goes to the bottom of each manifold, and 160 thermostat. It is getting cool here now,, so I was idling the engine for the full 10-15 mins until I seen the thermostat open up then gave it only a couple small quick revs,,, maybe it is condensation...

Just checked compression, all were between 172 and 190 psi. I ordered an Amazon borescope this morning, And I’m buying a good set of exhaust manifolds and risers from a buddy today…

Ok thanks. I assume that could get water in both sides? What about head gaskets? But what are the odds both are bad,,,,

Boat was only fresh water used it’s whole life until I bought it 4 years ago. It never sits in the water and I flush it after every use

Not really, in my picture,,,,the middle two were each side front cylinders, working out each way to the rears on each side.