check valves for exhaust system, help needed

[fiscoral]

installing an exhaust system in a restored 1978 chris craft 22 inboard tournament fisherman. Installed a crusader 5.7mpi and now running the exhaust hose which is 4in. dia. The way the exhaust sytem is run is under the deck and a low spot is formed where the hose matches up to the Vernatone mufflers( mufflers at waterline level) and then the exhaust hose rises 3 inches or so to exit through the exhaust tips out the transom. In short there will always be water collecting in the mufflers due to the low spot. The Crusader manual states that a 12in. minimum drop is needed from the top of the risers to the waterline, in this case my drop is 16.5 in. so i feel im ok. The low spot in the exhaust at the mufflers concerns me due to possible water ingestion.
will installing the Vernatone check valves help safe guard against water intrusion, but the check valves will be on a 25 or 30 degree down slope in the exhaust hose and im wondering if they will still work or do they only work on a horizontal or level install. Thanks for any info one may have, im loosing sleep over this!!! its a brand new engine, o hrs and im concerned!

[BigosS]

Is there not enough room under the deck to raise the mufflers so that you have a continuous downward slope? The spring-loaded but unreliable flapper valves I have seen would work even on an angle, but they are far from watertight and only protect against pressure backflow when the engine is running.

[fiscoral]

no thats my problem with the height. the mufllers are at max height due to the deck hatches. if the install is a problem ,i believe i may have to remove the mufflers and go straight out exhaust with no mufflers, not sure how loud the noise will be then. the original set up had no mufflers and smaller exhaust. running at cruising speed should not be a problem with the current set up(posted earlier)good outflow angle, its the slow trolling and throttle a little above idle which concerns me.

[BigosS]

Maybe get rid of the existing mufflers and look into those little mufflers that attach outside the boat to the exhaust thru hull fitting.