Safest way is to buy a Corsa Speed Switch. It wires into the tach and opens the exhaust at 3000rpm and will close it up when you back down to 2500rpm if you leave the switch closed.You can still elect open all the time with the manual switch. That what Formula uses on all blue motors,and you won't have to worry about forgetting to open it. Robert

I don't know for sure, but it might be because most boats without thru hull exhaust are not high performance engines.

Maybe not high performance by aftermarket standards but thru prop exhaust is still linked to many 350cid now 377cid and past 454cid motors. The Y pipes used before and now are the same in both situations, the only diffrence is the switchable exhaust to my knowledge.

Exactly, I had a 460 BB ford King Cobra in my donzi z25, that ran 60 all day long stock, through an omc outdrive, thru hulls w/ silent choice got me an extra 2 mph, as it opened it up, but I ran it many many times through the outdrive at WOT...

I have a friend with a Baja and a 454 that only came with through the prop exhaust, he since added corsa so he could run throuhg the transom. I dont remember him saying anything about not being able to run more than 3000 rpm's. Beakatlast this is Doug's boat I'm talking about.........24' Baja, it ran over 60 through the prop from the factory.

There are plenty of cruisers with 496 ho's running thru the props.
I've never heard that you cant have your silent choice on at higher
rpm. I've had 2 boats with it and never had a problem. Both boats
had 500 hours on them.

Your exactly right sledkachina, Doug's boat is a perfect example thru the prop from the factory. I would consider a Baja a high performance boat.

Yes...

on my 525 EFI I ran it with the exhaust closed thru the outdrive at about 2 to 4K RPMs when I had the women out for a ride and they wanted to chat ... when I put the exhaust into thru hull mode it ran fine... but when I put it back thru the outdrive it splattered exhaust residue all over the back of the boat... Pier 57 said to run the exhaust thru the hull... open ... at anything above idle due to that engine needing to breathe.

I took off the Corsa and went with shotguns. engine compartment looks so much cleaner looking http://www.drewmarine.com/