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525 Silent Choice use

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Old 07-12-2007, 08:00 PM
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Question 525 Silent Choice use

I've reading in the tech forum about someone who lost their engines, most likely from Corsa diverter use. I have a Silent Choice system on my 525 and although I rarely use it, I don't want to cause any problems with my motor. On a longer cruise I would like to use it so I can listen to the stereo and sometimes I have to use it at boat ramps in residential areas along with canals with homes. I have read somewhere that 3500 rpm is the max and I've read 3000 is the max. I read don't use them at idle and I read it's ok to use them at idle. I've noticed that my system does not completely divert everything down under. I still see water coming out of my pipes at an idle along with some noise. (My system just gets rid of the low end rumble and I can still here the normal "ticking" noise associated with exhaust.)

Do not need another repair bill!!! The last one was big enough!!!

Very confused....
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Old 07-12-2007, 08:29 PM
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Welcome to my HELL! Good luck getting 2 answers that are the same.
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Old 07-12-2007, 08:29 PM
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Blue motors don't like back pressure above 3000-3300 RPM. That's why many builders use the Corsa Speed Switch. It's wired into the tach to open the diverters at that rpm.That insures that you won't forget to open them yourself.
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Old 07-12-2007, 09:10 PM
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Running at idle or low speed(under approx 3000 thru the prop )should be fine,over 3000 is where a problem could develop,hence the speed switch to open the diverters
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Old 07-12-2007, 09:18 PM
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I don't use the Corsa though. I have Silent Choice (air-actuated) I don't know if there's a difference between how the two run. I do know that my system does not fully seal off the thru hulls and the best I can tell, it looks like all the water comes out of the thru hulls. I have ran it on the trailer and at least at idle, I saw no water come out the Lower unit. I have run the setup at idle before and briefly a couple of times at 3500 rpm. The longest stretch I have ever run the system was through a big manatee zone on the St. John's. I was at 1500 rpm pretty much the whole time. I will also call Merc tomorrow, but still need as much input on this as possible. THX
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Old 07-12-2007, 10:09 PM
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If I understand this correctly, we are not supposed to close the Silent Choice when cruising above 3500rpms on the 525EFI motors?
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Old 07-12-2007, 10:18 PM
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Not sure on Silent Choice. However, most are saying don't run over 3000 rpm's with Corsa Captains Call exhaust. This type of exhaust has a "Y" pipe that diverts the exhasut/water down through the drive in lieu of thru hull.
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Old 07-12-2007, 10:25 PM
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Quote:
Originally Posted by THLWL View Post
Not sure on Silent Choice. However, most are saying don't run over 3000 rpm's with Corsa Captains Call exhaust. This type of exhaust has a "Y" pipe that diverts the exhasut/water down through the drive in lieu of thru hull.
I still have the same type of diverter but I've noticed that I'm still putting out some noise and a lot of water thru my thru hulls even though the butterflys are closed and sending the noise "downstairs" Maybe this system is different than a Corsa as far as water flow and I have less to worry about. That is the big question. Not only will I call Merc, but I will call CMI tomorrow as well.
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Old 07-13-2007, 08:51 AM
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Quote:
Originally Posted by UNSANE View Post
I still have the same type of diverter but I've noticed that I'm still putting out some noise and a lot of water thru my thru hulls even though the butterflys are closed and sending the noise "downstairs" Maybe this system is different than a Corsa as far as water flow and I have less to worry about. That is the big question. Not only will I call Merc, but I will call CMI tomorrow as well.
My Corsa Captain's Call behaves in the same manner. Some exhuast and water still route out through the thru hull pipes even with the exhaust in the closed position.
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Old 07-13-2007, 10:41 AM
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You will always get some noise and water out through the thru-hulls. With my old system the overlap in the cam combined with where the water entered the exhaust stream caused water to get back in the engine and go kaboom. If your diverters are really close to where your risers end this can be a problem. The guy that rebuilt the engine said it is the worst after running the quickly backing off to idle. Still lots of water coming out he exhaust combined with little back pressure combined with high overlap of high performance cams equals big $$$$$$$$$ repairs. I miss the system when idling and listening to music. But then again if I wanted to go slow and listen to tunes all day I would have gotten a sailboat.
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