Logo
FULL SITE MENU

Exhaust Risers

J

jphillips13

New member
I have twin Crusader 220 engines in my boat. I have owned the boat for over 12 years - previous owner put OSCO center riser manifolds on the engines. It is a half system. I'm getting 4 years from each replacement so I can't complain but I'm preparing to replace the manifolds again and I'm considering changing them to the 4" exhaust risers. Has anyone increased the riser size from 3" to 4" exhaust to increase water flow? The 4" risers look to have a better casting and less restrictive water jacket - using OSCO / Barr center riser manifolds.
 
Going to a 4" exhaust won't change the water flow thru the system...the only other reason to go to 4" over 3" is to mitigate exhaust system back pressure and I'd be hard pressed to say a 220 would be in that condition....

We did a similar swap (to center riser manifolds and from 3" to 4") on the big blocks a while back...not hard but much more extensive than originally thought.
 
Have you noticed the difference between the water jackets on the 4" vs 3" risers on the exhaust end? I've replaced risers on OP fresh water cooled boats and it looks to me like the 4" risers should maintain better flow longer. Maybe I'm just being an eccentric old man.
 
Agreed the VOLUME is larger but the water still needs to exit out the little hole in the elbow and I can't say I've ever seen a difference there....maybe the casting have changed but I'd bet that hole didn't change much, if at all.
 
Back
Top