They can rate it at whatever they want to rate it, but this is the deal on a 5.8 Ford.
The intake used by pleasurecraft is the ultimate torque-monster, making all of the torque at about 2400rpm, this is what makes it easy to lay on power to get someone up, then let it off easy so the skier doesn't fall. If you have ever put a hot 350 in a boat, then you know it is somewhat hard to control (with high horsepower).
The carbureted 5.8's can spin to about 5000rpm or so with the stock intake and 13x13 prop, if you replace it with an edelbrock Performer RPM, or other de-restricted manifold, it will spin quite a bit faster.
Just like with Chevy's LS-1 motor, the H.P. rating is all about where the rev limiter is set. If it set to 5650rpm, it is 345hp, if set to 6250rpm, it will make 405hp. The torque is about the same on the Camaro SS and the Corvette, with 50hp difference in what is basically the same engine. Torque is what matters on tow boats, and the HP rating is all about where the manufacturer, PCM, decides it to be.
If anyone wants to see the stock restrictor plate that came with my 1988 PCM 351 Windsor, I can email it to you, my email is
[email protected]
It is the smallest V-8 manifold I have ever seen, the plate only lifts the carb or lengthens the intake track length.