In your jet boat application, they might not be as effective in a couple of ways:
- You may not feel any difference in power because your jet pump is not hooking up until about 3000 rpm and above, and so any gain in torque will be unnoticed
- The D3VE head has the poorest flowing exhaust port of all the 460 passenger car heads, and they begin to back up at about 4000 rpm. And since the jet boat engines typically run above 4000 rpm, you might not see any upper rpm gain either.
However, this is all correctable.
If you install a set of ported, large-valved D3VE heads on your boat it will make significantly more power, expecially with the tunnel ram and headers. And it just so happens that I have a set of ported D0VEs on the shelf ready to go and also just finished a set of ported D3VEs ready to be machined and then they are done, too. These particular ported D3's are a budget porting setup. Aren't you somewhere around Modesto? I am in San Jose.
I just watched your video again and to me the engine sounds like it runs nicely....are you sure you want to mess with it? At least maybe enjoy the summer and then you can do the head swap in the off-season.