Using throttle in reverse is highly unlikely to cause this if you you look at the muffler plus increased exhaust pressure when that is occurring. I would enlarge the drain on the bottom port side of your muffler to drain the salt water out of your muffler before you flush the cooling system after use. There is quite a reservoir in these mufflers so a source of back corrosion while the boat is sitting if the system is not flushed for a long period of time......about the only extra thing you can do that I can think of off hand.
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Thread: Etx cat manifold problem
04-14-2013, 08:08 PM #2109 21v LAUNCH
run your engine after you change your oil
68 th Member. WS420,HSE Revolution, OJ 466, Acme1157,1100 sacs,Kicker HLCD's n IX500.4, Supra Coolies