I am installing a HP525 EFI in place of the 496 HO in my 2005 Donzi 22 Classic. I would like to keep the Q&Q but am getting a lot of conflicting info. In my application the Corsa diverter is very close to the header collector, especially on the starboard side. This motor has a fairly aggressive cam with duration @ .050 of 236/244 and high lift over .6 exh & int. My service manual says that this motor can be used with Q&Q but only up to 2,500 RPM which is OK with me as I'd only use it while idling around marinas or trying to talk while idling. There are a lot of 525s in service here and I wonder how many of you have Q&Q on them? Are your diverters located downstream or right near the collectors like mine? Should I just play it safe and order new longer tails and give up the Q&Q? Obviously reversion is my concern from water entering the exhaust so close to the collector. TIA.

I am not a expert here. But I use long exhaust risers that mix the water as far from the engine as posible. That cam has a lot of duration for short risers & diverters.

Some folks have had success with the Corsa Capt Call system. However, in 2006 when my motors had 90 hrs on them, I stuck valves in both heads on both motors. Merc Racing contributed the issue to my "modified" exhaust which is the Corsa system. I removed the system and went with the factory system per MR instructions. However, I continue to stick valves so I don't really have an answer for you. But the 525 efi is the most agressive cam system MR builds and at idle is where I was getting my issues. MR wants 750 rpm min at idle to prevent reversion so check yours when done.

Thanks guys. I'm leaning toward losing the Q&Q.

That is to bad, You should call corsa marine teck support and see what they say first, I believe all there systems are made that way. Good luck with it.

I personally don't like switchable exhaust systems in use now on any high performance big block engine.
For quite a few good reasons:
1. Quick and Quiet and Captains Call and Silent Choice were all developed back in the days of small block motors and mild big blocks only.
2. If you look at the hole at the bottom of the Y-pipe you will seen outlet which measures approxiamtly 2" by 2-1/2" in size and some constricted turns to get there. Think about it , you are going to squeeze exhaust gas thats flowing out two 3-1/2" to 4" pipes and route both through that single constricted hole-not a good idea -especially when you have a real high performance big block engine with a moderately agressive camshaft.
3. They should only be used at idle, but that's where potential reversion issues on an engine are at their worst.
4. What if you or an un-familar driver of your boat forgets to hit the switch and open them soon enough, it might be to late to stop the damage that could occur.
5. Most locales, states and Noise Nazis have currently & actually outlawed their use and more are subscribing to that requirement to outlaw switchable exhaust!
6. Get any manufacturer or distributor of these switchable systems to warranty the damage or potential damage you could do to most high performance marine engines -Ain"T Gonna Happen!!
I could go on with reasons but I think you can see how I feel about these systems. Not my preferred choice for noise control and good engine life combined. I could go on here but I think you can see how I feel about these switchable exhaust systems. Need to control the noise of your performance boat , then use some of the good muffler systems currently on the market!

I also think its about time some of our better boat builders started incorporating some of the noise chest technology symilar to Mercury Racings external add on units only done in fiberglass integral and internal to the hull.
The future will require a better noise control systems on performance boats, so lets get it done before the political beauracrats start over legislating the issue in the near future and create a bigger problem for our sport!

I know some of you think Aw- Screw It, we like the noise, the louder we can get it, but I don't want to think we all will loose the sport and recreation because a few performance boaters are to selfish to make a compromise for reasonable exhaust noise levels. Besides, noise is not a true determiner of the performance levels of engines and boats, as some turbine powered boats demonstrate!
No one likes the great sounds eminating from a high performance engine any more than I do, however I am not going to cut my nose off to spite my face and loose the sport I love! I'll put my soap box away now.

Best Regards,
Ray @ Raylar

Thanks Ray, you help a lot of people out here and I appreciate your advice. I think I will lose the Q&Q and maybe add switchable tips in the future. I do like to let it roar and on the Great Lakes I'm not bothering anyone. The Q&Q was mainly for idling around the marinas. I guess no more idling around the yacht clubs for a while to admire the big boats