I have a 24 baja outlaw that I am getting ready to put a 565 in. I have a set of stainless marine manifold and what I think are standard risers. They go up about 4" and are 6" long. My question is would it be fine to just cut the risers in half and add say a foot extra pipe. I have a friend that can weld stainless that said no problem. I just dont see people on here doing that didn't know if I was going to affect the water cooling or not. We can do it for around 100 and that is way cheaper than having them do it.

i sure you know that the riser is double walled 3"ss pipe.it can be done.i just had my risers cut and shortend.

3" and 4". My question was more if I would be hurting anything like cooling. I don't want any reversion. So I was going to try and make them as long as I could. Didn't know if I should just try and make them go out the back of the boat.

If you can make them I would say go for it and I would be interested on how and what you do.
No cooling issues. Merc sells riser extensions it's just they are cast iron and suck.

yep, works great! just obviously make sure you extend the inner and outer tubing on the riser. i had to have this done on my danas cause i was getting reversion from my new cam

I just had this done 2 weeks ago. stainless marine exhaust with standard risers. Had them extended all the way through the tips. No more rubber hose. I had about $600 in stainless tubing. Also make sure to use the good graphite gaskets and not the green cheap ones, they are junk.

just be sure you are cutting risers before the holes that allow water to mix with exhaust. otherwise you aren't changing anything.

I extended the risers on my Imco's all the way to the tip and just used a short rubber coupler to join the riser to the tip. worked great, but is LOUD. I cut off about 1" from the outer pipe so that I could weld on the new inner pipe and then welded the outer pipe in place. Be sure to install o2 bungs while you are working on them. They will come in handy at some time.