One thing on the offseason boat to do list for my Pops is manifolds on his 312 Fastech with 6.2s.

Other than stock replacements what else have people used? Stainless Marine, Imco etc? Any gains or feedback on them?

Thanks

Salt water is going to drastically reduce the options available to you. I know I did my homework when I did mine, gains weren't anything amazing for the extra money you'll dish out. Some claim 2-3 mph increase. Not sure if that's because they actually perform better or because of the weight reduction factor.

I'm pretty happy with my GLMs.

On a warmed up 350 mag with vortec heads and a comp XM270 roller cam I saw very little improvement running Stainless Marine exhaust. I would wager a guess the bit of improvement I saw was more from weight reduction than flow improvement.

I agree with above, with stock engines I don't think you will see any change going to a SM/GLM exhaust. I know I didn't, and have run both brands (GLMs were aluminum). I have SM now, but the GLMs were really nice for the price. They are near impossible to find in the aluminum version now.

The small single engine boat saw an improvement planing off due to reduced weight on the back, although I don't know if it would be much of a factor on a 312 that already has small blocks.

She does great getting on plane, just exploring all options before just bolting on stockers again.

Stainless Marine for the win. You cannot beat their longevity. Pricey, yes, but they'll last forever and should be a positive factor with regard to resale.

Ever thought about installing HITEK Exhaust's?

Those things are expensive, and I've heard that support is very difficult to obtain. The story goes that it could take months to get a warranty fix/replacement.