Help us modify this Mercruiser 502 exhaust system.

[Philster]

I am doing some work on the Scarab soon. I was going to put CMI headers on her, but I really don't need them, or the cost. I canceled the install.

I want to lose the big red "exhaust cans" that are part of the 'whisper quiet' exhaust from Wellcraft. They make an annoying, sort-of-tinny, sound that is hard to describe; they look past their prime (paint and metal failing) and I do want just a little more growl. I don't need obnoxious sounds, so I am going to keep the basic exhaust manifolds and exit locations.

The exhaust exits below the swim platform, and the exit location tones down any serious, potentially obnoxious sounds.

How would you go about this project? Am I looking at running a stainless steel pipe to replace all the red metal parts of the exhaust?

I am cautious before changing anything on any boat, so I always like to ask first.

Note: this thread is not intended as a platform for anyone to comment on loud exhausts. I am not putting on an obnoxious set of headers straight out the back. Sound off (no pun intended) someplace else.

 

[Bondo]

Re: Help us modify this Mercruiser 502 exhaust system.

Ayuh,... It Appears your plan ain't gonna work...
The outlets thru the hull look Higher than the outlets of the risers...
The waterlift mufflers allow it to work now,..

If you don't have Continuous fall from the risers, you'll get water back into the motor...

 

[Philster]

Re: Help us modify this Mercruiser 502 exhaust system.

Bond-o, I think the engine compartment pic is making it appear as if the outlets really are higher, but they are actually lower.

The risers start up near the engine cover, and if you look at exterior shots, the exit points are lower. Believe me, I ain't arguing with you, just explaining the layout that the first pic might not show! I respect you far too much!

If I can continue a reasonable slope from the risers down to the outlets, that would make it acceptable?

 

[Philster]

Re: Help us modify this Mercruiser 502 exhaust system.

Here are pics of a modified 502 exhaust in the same Scarab model as mine. The out-the-back exit is higher than even my stock exits. He managed a mild slope.

This should show that my below-the-swim-platform exits are well below the risers.

 

[Bondo]

Re: Help us modify this Mercruiser 502 exhaust system.

I think the engine compartment pic is making it appear as if the outlets really are higher, but they are actually lower.

Ayuh,... IF there's drop in there,...
All you need is the piping to mate the risers to the outlets...
Being it's gonna Have to be Custom,.. Start calling around to see just how Bad it's gonna set ya back...

 

[jtybt]

Re: Help us modify this Mercruiser 502 exhaust system.

OOOOOOO...That's gonna be loud

 

[haulnazz15]

Re: Help us modify this Mercruiser 502 exhaust system.

I think I'd go straight out the back like the second pictures show. Just cap off the original exhast outlets (looks like they made some sort of SS cover). No reason to make it really complicated.

 

[Philster]

Re: Help us modify this Mercruiser 502 exhaust system.

I've grown to like the exhaust directed down at the water, but the more I think about it, the more I am inclined to keep it simple and run a straight pipe to each tip straight out the back.

Get two straight pipes and cut some holes.... and close two off...