This is probably a stupid question, but I was wondering if anyone has tried to run a na 540 with through prop exhaust? With all the noise laws coming into play, rather than worry about what muffler to use, how much rpm or horsepower loss would you expect if the exhaust was run through prop?

You may be able to get away with it, but at first thought it sure doesn't sound like the healthy choice.

It may be harmful to the engine, to much back pressure and the such, burnt valves , etc,,,, . I know a very good engine builder who would know the real answer and why. Drop him an email, or you can contact him @ 516 216 0778. Ask for Jeff, tell him Bo said to call. Good luck

If not harmful, certainly won't be productive to building power. You'll proably be losing 50+ hp. Now if you want to be quiet through the marinas, then it's great. Just open up the diverters shortly after planing off.

Or, have your exhaust exit below the waterline or right at the waterline when at idle. Many checkmates are built this way. May take some work, but it will be worth it if you are going to run that big cube motor.

I think the open exhaust "tube" style Bravo, as opposed to the exhaust bellows style, is OK up to maybe 375-400 HP. I would think a 540 wouldn't be very happy.

A good example is the 496 which includes thru hull exhaust. There you are at the 400-450 HP range (flywheel)

Corsa "Quick-Quiet". Noise and power when you want...no noise when you want.