When can you use silent choice?
 

We have a 2000 38' Fountain 502 efis with cmi headers on it with silent choice. I've been told that you can only use silent choice while idling, is this the case? Or how fast can you run with the silent choice on?

Re: When can you use silent choice?
 

I think it depends on the motor... think about it, lots of non-Mag 454's out there only have through prop exhaust and they dont' have a problem.

Re: When can you use silent choice?
 

Thanks for the reply. I was told with it on it was hard on exhaust valves above low rpms.

Re: When can you use silent choice?
 

I recall seeing some systems that say not to be used above 3000 rpms.

Re: When can you use silent choice?
 

Idle

Re: When can you use silent choice?
 

I think I remember reading about the HP500 had to be open above X rpm, but for the life of me I can't remember the details.

Re: When can you use silent choice?
 

I asked the same question to a mechanic at a Baja dealership about My 496 mag ho with switchable exhaust. He said it's ok to run it either way, just don't switch it while at the higher RPM range, He recomended to switch at idle or low RPMs...

Re: When can you use silent choice?
 

I've ran mine at 75 with no problems... I've actually heard in some cases that it's better out of the hole since you have more backpressure which gives you more low end torque.... but that depends on the engine.
I got a few exhaust tip mufflers made so I don't need to run on silent choice on the busy weekends at Lake Havasu... I'm sure the exhaust running on silent choice doesn't help out the drive temps when it's 115 degrees out.

Re: When can you use silent choice?
 

Same here, I had Corsa on my donzi, only switch at low RPM, you could run WO either way, just no switching above 3000...

Re: When can you use silent choice?
 

There was a "Teague on Tech" article in Powerboat about six months ago that said motors with horsepower above 300 should have the exhaust open above 3000 RPM's.

Re: When can you use silent choice?
 

I learned the hard way. I have 454 Mag MPIs with silent choice. I forgot to turn off silent choice one day before cruising at 3600 rpm. I ended up blowing a hole in the exhaust y-pipe. Water ended up pouring into the bilge and getting everything wet. Really sucked.

By the way, JB Weld and a stainless screw got me through the rest of the season.

Re: When can you use silent choice?
 

I know that Formula's have a built in sensor that automatically opens the silent choice above about 2500 RPM......so I would figure that it would be bad to run it anything above that. Otherwise, why would they engineer some nifty thing like that???

Re: When can you use silent choice?
 

Thanks for the replys.

Re: When can you use silent choice?
 

I agree.

Re: When can you use silent choice?
 

This is how I've always played it, and it sounds like from the uncertainty above it's the safest bet. I'd hate to replace these things for using them wrong. But I only use them for when in no-wake zones; docking up at a restaurant where it could be obnoxious to patrons dockside; engines running while doing maintenance etc; well you get the gist. If you tend to use them at 25-3000 rpm chances are at some point in time you're gonna slip and run them above those marks several times over the course of your ownership. Odds are they'll fail on the next guy buying the boat too....

Re: When can you use silent choice?
 

I have the Corsa and here's what I was told. Don't run it over 2500 RPM's. On the other end, under 2500 RPM's, I was told you can have vivration which could lead to reversion? It doesn't sound as good around the Gas Dock, but I am not going for a rebuild either.

Oh yeah, they guy who did the rebuild on the top end told me this. I have a 99 454 MPI and the metal gaskets rotted out. He would say the Corsa caused it, but he strongly recommended it go through the hub under 2500 RPM's

Re: When can you use silent choice?
 

i had it on the 502 in my cheetah, used it whenever i wanted, hi-low whatever, run it.

Re: When can you use silent choice?
 

I honestly can't see any reason you can't run it either way. How many boats are there out there that have just through the prop exhaust, are you telling me they could have problems running over 3000RPM??? I can understand not switching at RPM but other then that the only abuse I would see is the stress on the solenoids under load..

Re: When can you use silent choice?
 

I'm tellin ya you can run wide open with it on, my donzi used to only have the exhaust through the drive, I added it to go through hull. Why would some one say you cant run it through the exhaust? Does that mean that any boat that doesnt have thru hulls cant run wide open?:eek:

Re: When can you use silent choice?
 

RUN SILENT
Question: I have what I hope will be a simple question for you. I have a new 496 Mag HO with Corsa Captain's Call/Silent choice through-hull exhaust. I am wondering if there is a limit on how much rpm you can run with the exhaust "closed" before you should open it to the full through-hull position. Are there back-pressure concerns? What I have been doing so far is opening it when I hit 1,500 rpm.

In all the literature I've read, nothing has referred to a limit or suggestion regarding the rpm you should open the exhaust. I'm guessing this may be something I don't need to worry about, but I wanted your opinion.

Mike Shaver
Canton, Mich.


Answer: I think that you are being more conservative than you need to be. I would be more concerned if your engine were supercharged, or made 500 horsepower or more. I would say that you can run constantly at 3,500 rpm, which would allow you to cruise in the quiet mode. If you inadvertently run full throttle for a short burst, it probably won't hurt anything either. The system does create a little more back pressure. If you try a comparison at full throttle between open and closed, you will probably notice that it takes longer to get to full speed with the exhaust closed, and that the rpm is a couple of hundred less than when the exhaust is open.

Powerboat Magazine, Teague on Tech, Sept. '03

Re: When can you use silent choice?
 

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

Re: When can you use silent choice?
 

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

Re: When can you use silent choice?
 

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.

Re: When can you use silent choice?
 

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...

Re: When can you use silent choice?
 

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. :eek:

Re: When can you use silent choice?
 

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.

Re: When can you use silent choice?
 

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.

Re: When can you use silent choice?
 

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 :rolleyes: ... 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.

Re: When can you use silent choice?
 

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