340 Reversion/Inversion Resolve - Did it work?

[SeeYa Ray]

Hello Everyone - Im experiencing some water pooling in both engines in the exhaust manifold on my 2000 340 Sundancer w/ 7.4 MPI engines. This was a project boat that I bought last year with rebuilt engines, however the boat was inoperable and none of the "fixes" were on it at time of purchase. I read where many have had the dreaded reversion/inversion issue on their 99-01 340's with 7.4 MPI/330hp and 380hp/Horizon mercs. It looks like 3" spacers were added to the risor height to increase the degree of slope on the exhaust tubes and then resonators installed inside the exhaust tubes to help cancel out sound waves. I added 3" spacers, but still getting water in the Ex manifolds. Could someone who had this done, keeping the log style exhaust collector on their 340, give some input on how well this worked or didnt work for for them? Much appreciate it!

I also read that some had a water lift exhaust system was installed their boats as well.

Anyone?

Below a pic of the resonators

 

[Golfman25]

I’ll need time to pull all the info, but there where generally two fixes. 1) Changing to a water lift muffler system - complete redo and retrofit of the system. I think it was mostly done in salt water environments. 2) spacers and resonators added to the system. A lot of those by me in the great lakes.

 

[bfernald0]

Here are the service bulletins. I took out the log system and installed waterlift mufflers on my 340 when I repowered from 7.4s to 8.2s.

 

[Stee6043]

My 99 340 had the water lift mufflers installed. I was under the impression that this was the "official" fix for the reversion issue?

But I also thought the reversion issues were only with the horizon motors. Do you have the horizon's?

 

[SeeYa Ray]

Thank you Bfernald for posting the bulletins. Very helpful info!
Stee6043: Like that dingy off the back of yours. My engines are not the Horizons, but the lower 330HP version. Here's a pic

 

[Golfman25]

My 99 340 had the water lift mufflers installed. I was under the impression that this was the "official" fix for the reversion issue?

But I also thought the reversion issues were only with the horizon motors. Do you have the horizon's?

It was primarily on the Horizons due to the valve overlap. I think many “fixes” where done on the regular 7.4s for comfort. I looked at probably 20 or so around me and none had the water lifts, but all had the spacers and resonators. The bigger problem was soft decks.