Is this something I'm overthinking?

[onlybillhere]

So we went out this weekend for Labor Day festivities. Normally it's just me and wife and not a lot of other things (a small cooler and maybe an extra 5 gallon gas tank and that's about it), the pontoon will get me up to 18mph turning around 5500 rpm (pretty much the sweet spot at WOT). So we brought another person with more stuff (bigger cooler), probably added another 300-350 pounds including the person than what we normally do. was turning 4500rpm (wot) and about 13mph.

so my question is should I be dropping that many rpm's for the extra weight added?
Also If I change the prop to get me back into the 5500 rpm with the extra weight i would need to lower the pitch (currently running 10.6" x 12 pitch) but would that make sense to even do? I normally run the boat with just me and the wife half the time and loaded with extra person(s) the other half.

[riplipper]

350 lbs is probably close to 15% weight gain for your boat so yes it will hurt performance.
Your wide open RPMs with normal load should be equal to the engines maximum RPS.
If you cannot get to max rpms for your motor, there is most likely a prop issue which fixed will help with the additional weight issues.

[BobL]

The load lugs the motor rpm's down just like climbing a hill in high gear in your truck. Now throw in hundreds of pounds of concrete in the back of the truck, unless the wheels are losing grip, the RPM's will go down. The truck performance under load can be controlled with gears but the only "gear" control you have on a boat is via the prop.

Same thing on a boat. With extra weight, and slower top speed, the only way the prop is going to spin as fast is if you have a lot of slip (prop pitch).

Enjoy the boat and friends and go slower when there is a lot of beer on board.