I don't want to get any reversion problems but wondering if there is a max rpm for using the corsa thru-prop vs. transom? This 509 sounds pretty damn rowdy at idle with 10.2-1 C/R and a Marine Kinetics .600" lift cam....... I have about a 15 minute run past at least 100 waterfront homes at idle power to get to the open bay....... This thing sounds downright angry with no mufflers!
My marine guy did a great job moving the transom exhaust holes up about 5" as the 496 exhaust with the tall risers was way higher than the stock 502 setup.... Plus I like the idea of the flappers sitting above the waterline...... TBF

The hole through the gimbal is actually quite small like 1.5"-2" diameter and from there it is a long uphill stretch to the headers, I don't think you would have any reversion problems, but I wouldn't use the through prop at much above your minimum planing speed.

I read on here somewhere that 2500 RPM was max

Do you have the accordion exhaust bellows connected to the drive? If so might investigate replacing that with the tube type so the exhaust isn't forced to go thru the prop reducing back pressure

I also heard 2500 r.p.m. Very considerate for you to be thinking about the noise level.
Always a good idea to look out for the performance boat image before it becomes a problem.

Well, it was not too bad.... Idle speed is not too loud but when I put a load on it holy crap! I came in at sunset and anytime I come in late I will keep it thru the prop.... I do have the accordion style tube so maybe I will change it over....... Thanks.....

Yep, 2,500 is what the Mercury 525 manual says. I only use it at idle when I need to.

Video clip of boat running on the hose so we can hear the cam?

For reference...There are cruisers I run with that are straight thru prop exhaust with BBC's. I can't see those being much different than a HP motor being ran with closed exhaust at a lower RPM for the range you are referring too. Not like you are wanting to run WOT with exhaust closed, while these cruisers do it w/o issue.

i was thinking along US1's line of reasoning. 260 thru 330 hp uses thru prop as only option. if your secondaries aren't opening, you are probably not into too much back pressure.