Twin 93 Mercury 200's have low RPMs at full throttle

[93Robalo]

I have twin 93 mercury 200's 2 stroke carbuerated on a 2320 Robalo. I bought the boat about a year ago (bad mistake) and have had problems since. BOTH motors only hit around 2100 RPMs under load, full throttle and will NOT get up on plane. I've replaced both primer balls, fuel filters, and water seperators. Any help would GREATLY be appreciated. Ive been pulling my hair out trying to figure out whats going on. Ive had a compression test a few month ago and was told they checked out ok. Its weird that its happening on BOTH motors and not just one. Could it be dirty pick ups in the gas tank? Also the props that came with the motors are 21p's could they be to big for the motors? I dont know if its a fuel issue or electrical? The fuel pumps seem OK.

 

[aussieflash]

Re: Twin 93 Mercury 200's have low RPMs at full throttle

The only thing they share that could cause that problem at the same time would be fuel and load.
Carbs may have clogged jets and need service/cleaning etc.Check tank and fuel pickups are clean and vents are working.
Wet/water logged hull could make planing difficult,though unlikely with twin 200s.
It has to be fuel related.

 

[93Robalo]

Re: Twin 93 Mercury 200's have low RPMs at full throttle

Thats's what I thought maybe its fuel related I had the carbs rebuilt a few months ago but I found water in the fuel this time around. It might be a good idea to rebuild them again. I definately need to get to get to the pick ups and see how they look. Do you think it could be the power packs that aren't allowing me to get proper RPM's under load?

 

[Robs88]

Re: Twin 93 Mercury 200's have low RPMs at full throttle

I would bypass the fuel tank on boat, run engines directly on a 6 gallon portable tank see if engines do the same thing.