Water Injestion

[LAD]

My current 7.4 L EMI gas engine has suffered from water ingestion due to valve overlap. Has this problem been solved with the newer 8.1 L engines?

[mongo75]

How does valve overlap cause water ingestion? Valve overlap is normal in all engines for improved cylinder scavenging. I know I didn't answer the question, but if you have water ingestion, you got a problem that needs addressing before you go looking for a new motor.

[LAD]

Unfortunately,the problem is not just mine. Boat US Magazine ,Jan.,2003 discusses the problem(s )with GM engines that were marinized .
I am looking for info on latest ,8.1L,marine engines and their performance todate.

[mongo75]

Gotcha- I was scratching my head trying to figure out how water would get past the risers, which is why I thought you may have had a cracked exhaust manifold or something. Do you know what caused it? I'd like to know for my own knowledge.

[redtech]

Hey Gunny, scratching my head too, but i'm going to look boat us article and read it before i say much more. i do recall something about exhaust elbows creating a water ingestion problem but have to look back into books to find out why.
as for gm engines in boats very few ever come into the shop for this

[LAD]

Apparently, the design of the elbow and exhaust manifold make a difference at lower rpm's where water and vapor work backup and fall into bottom of manifold ,hence heads and valves. Thats the best this amateur can interpret the work by the pros.
Baffles ,lips ,crossover pipes ,etc. have been used to address the resulting frozen valves,rusted cylinders and bent pushrods.

[tom kane]

Any marine motor that has a conventional wet exhaust will always be prone to the many problems this system creates. The only answer is a dry exhaust that is jacketed and cooled with water, with the exhaust water injecting to the last few inches of the system to reduce noise.A dry insulated primary exhaust section (headers) plus water jacketing the rear section is good and does away with plastic and rubber exhaust which fail if water cooling stops.

[Frosty]

Google reversion.
High performance cams with duration and overlap can cause this.

Marine cams are designed not to do this .

[tom kane]

search Hardin Marine Cyclone Headers.It has a lot of info.

[LAD]

THANKS- I am restricted to repowering with an 8.1L GM based engine for reasons of space , mounts,etc. This led me to original question. Three marinizers I know of have gone to the 8.1L and have what appear to be different exhaust manifolds and water injection elbows. Have any or all solved the water injestion problem with a raw or fresh water cooled engine?
The 7.4 engine was a nightmare.