Could not get on plane
 

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? :head:
Merc 200hp

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.

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.

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

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.

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

It could be any number of things. Did it run even under load or was it rough? Did you drop any cylinders at WOT? Check fuel, carbs, timing as already mentioned. See if you can diagnose it as spark or fuel problem. If you put it in the water you can test spark under load. You might try choking it while trying to plane. If a float is stuck it would enrichen the mixture and make it better. My 250 was laying down similar to what you describe and I had a bad stator. Let us know what you find.

I checked compression and I have 4 cylinders at 116 and 2 at 120, so we're good there. I took out the sound box and sprayed a can of carburetor and choke cleaner on all three. The timing advance arm moves freely and I would like to check the ignition timing adjustment, but I have misplaced my manual and don’t remember the setting or procedure for this Merc 200hp.

try running the boat again and see if it picks up when you push teh key in for chaoke, it sounds like thte carbs need to be gone thru, spraying carb cleaner down thru the carbs dosen't do much, you have to dissasemble the carbs to clean them out properlly

Spare, if I understand you guys correctly, even if the motor ran and idled perfectly when I was by myself and the problem only started when I had an additional load (six people in the boat), I still could be looking at a fuel issue?