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drilling exhaust/midsection mercury?

All the XS racing outboards have exhaust exits right above the cav plate. They are "built in" so to speak. They are louder than the non XS motors but not an annoying loud. My 300XS motors were only "loud" at 5000 rpms or more.

I use to drill the mid sections on all my older mercs and install the Bob's snout which would do two things: cover the holes so it doesn't look stupid and enable you to plug the holes if you want quiet. Again louder but not annoying. No hp gain but enables certain props to move out better. You won't gain any hp unless you remove the can or "inner liner" and modify the tuner...then it will be loud.

-Craig
 
Craig said:
All the XS racing outboards have exhaust exits right above the cav plate. They are "built in" so to speak. They are louder than the non XS motors but not an annoying loud. My 300XS motors were only "loud" at 5000 rpms or more.

I use to drill the mid sections on all my older mercs and install the Bob's snout which would do two things: cover the holes so it doesn't look stupid and enable you to plug the holes if you want quiet. Again louder but not annoying. No hp gain but enables certain props to move out better. You won't gain any hp unless you remove the can or "inner liner" and modify the tuner...then it will be loud.

-Craig
Click to expand...


hey man! i have twin 1998 225 promax motors. i just drilled my mids like the factoty ones your talkin about.(above the cav plate) and removed my liners and drilled my exhaust tuners like Jay Smith suggested.

what kinda gains are possible with this mod??? gnna be testing tomorrow.

thanks!
 
enchanted said:
see this sounds really good, where did you drill it and what size holes? pics would be very helpfull. ive seen people drill the bottom of the mid section pointing straight down at the cavitation plate and also at the back of the mid section pointing out to the sides above the cavitation plate. i was thinking of doing it pointed out the sides at the back. any thoughts?
Click to expand...

I drilled one 2 inch hole and then installed a Bob's Machine exhaust snout as per the directions that came with the snout.

http://www.bobsmachine.com/Products/engine_exhaustHousing.cfm


John
 
2tonchevy said:
hey man! i have twin 1998 225 promax motors. i just drilled my mids like the factoty ones your talkin about.(above the cav plate) and removed my liners and drilled my exhaust tuners like Jay Smith suggested.

what kinda gains are possible with this mod??? gnna be testing tomorrow.

thanks!
Click to expand...

I don't know....5hp maybe...50-75rpms? -Craig
 
Relieving the exhaust only... will make it louder. To gain performance you must also do something with the water. Either dry stacking or a poppet diverter helps with low to midrange acceleration. These re-route the water away from the exhaust. Without any water to "push out" you have a truly free flowing exhaust.

Personally I like the loud 2 stroke sound. However, when you have any non boater passangers with you they tend to cry about the noise a bit.

Hope this helps.


EDIT: Get over on scream and fly and do some searching on this topic. You will learn what many others have done.
 
There is no whining allowed on my boat. :)

Seriously though, I've had a lot of non boaters on my boat like my mother in law, friends of my wife, and never had any complaints. If I ever have the powerhead off I'd love to dry stack mine.

John
 
I would maybe do it if there was something to gain...but dont enjoy noise much any more.does it run better?Faster?better on fuel?i went fishing last week and only burned 3 gallons of fuel and i was blasting around alot! OMG i sound like a sailboat guy talking about how much fuel i used:eyecrazy:
 
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