Could not get on plane

[BuilderFL]

Took the boat out yesterday for a test drive by myself and was working fine.
1. One person on board (200lbs)
2. Idle was steady at 800-850 rpm.
3. Throttled up real good and got her up to 39 mph at 5200 rpm.
Believing everything was good to go, I called the wife and kids for an inter-coastal night ride.
1. Six persons on board (965lbs)
2. Idle was steady at 800-850 rpm.
3. Could not get on plane, would not go beyond 7.6 mph and would not throttle more than 2200 rpm.
All other things equal.
I did notice that on neutral, the throttle would rev up to 5500 rpm but in gear did not have the power to move the boat.
Any ideas as to what’s going on?
Merc 200hp

[bcmarinamanager]

Could be that one or more of the carbs, decided to quit working. It would still rev up high, but when under a load you get almost nothing. I would bet either the fuel pump or something else with one of the carbs. I had a similar problem with my 1992 200 merc not long after I bought it, and it turned out to be the fuel pump was sticking.

[THEFERMANATOR]

Also go back and look at the timing advance mechanism. When engines set-up for awhile the timing mechanism is known to stick and you don't get full timing which will knock you down to about 2K RPM's and just feel doggy.

[spareparts]

5200 @ WOT is a little on the low side with a light load, has it ever turned more rpm with teh prop you have, you may need to drop down in prop size to carry a load

[BuilderFL]

Done almost 40mph at 5600 rpm but don't like to push this old motor that far. I've had this prop for many years and has served me well, both with or without a load. What's mind boggling is that with the throttle all the way down ( and the fuel consumption that goes along with that) it would only do 7-8 mph at no more that 2200 rpm.

[spareparts]

like ferm said, check the timing advance, its teh arm on the side of the block that moves the pick up under the flywheel