Changing to center riser exhaust manifolds.

There's a good chance that I'm going to end up having to replace my exhaust risers, and if I end up having to, I'd almost just as soon replace the whole mess.

I hear the center riser exhaust system flows better, is less susceptible to water flow reversion problems, and they seem to be cheaper and more readily available. I'd rather just replace the whole mess now, and sell the (still good) manifolds to recover some cost. Even if the risers are still okay, I might go ahead and do it now...

Anyway, couple of questions. Obviously the risers are different. What else am I going to have to buy to make these risers mate up with my Y-pipe? Is there anything else involved in doing the swap?

Also, is it better to go with aluminum or cast iron? I'm thinking Aluminum would weigh less, last longer, and dissipate heat better.

Is there a reason that Aluminum ones are less common?

Re: Changing to center riser exhaust manifolds.

From what I've read and heard, the aluminum risers don't hold up as well in salt water. In addition, the difference in coefficient of heat (expansion/contraction rate) between the cast iron heads and/or manifolds and the aluminum risers leads to leakage at the joint. In addition to the risers themselves, you're going to need the short 3" or 4" hoses leading back, the elbows down, and the short hoses to the "Y" pipe, plus all the hose clamps. Depending on your original setup, you may need some bracket changes to mount the starter relay, ignition module, and/or shift mechanism. It is definitely a do-able change, and well worth the effort. You can usually pick up a kit that contains all the necessary parts, down to the mounting bolts. That's what I did on my previous boat's 350. Worked like a charm. Good luck. Hy

Re: Changing to center riser exhaust manifolds.

So for a freshwater boat, would aluminum manifolds be the way to go?

Re: Changing to center riser exhaust manifolds.

So for a freshwater boat, would aluminum manifolds be the way to go?

Click to expand...

Ayuh,.... That's the way I'm going with 1 of My project motors.....

I gotta believe you'll be cuttin',+ fittin' something Custom to get the riser outlets to line up with the Y-pipe,...
Probably need another elbow to make the turn down...