1998 225 off-shore, carburated.

I traded for this engine from a source I trusted. First time out engine idled fine at 900 rpm. Engine would not run right, above 900 rpm. with a load on it, on the water.
The carburetors were serviced over a year ago and the boat sat until this weekend. The service tech said he didn't remember if he drained the fuel before the boat sat. So it could be the carbs need to be redone. That's my fault.
I did see some other things on the engine that concern me. I'm not a mechanic. I would like more info/diagnostic input before I continue on with this motor.
Thanks!
PS. This is a mercury outboard

check the compression and the spark with a gap tester...then get back to us...if you do not know how to do this then insist that the tech do this first...tell him if the compression is bad then stop..you have to make a decision on whether to repair it as you are looking at a lot of money..especially if you pay for it..if the spark is bad let him do further diagnosis....

Thanks papyson,
I have a best friend who is a real good mechanic. I don't trust the boat guy, so my buddy and I are going to do the diagnostic work. We're going to test the compression in a couple of days. We already re-set the plugs.
Will let you know.
Thanks again!

Have him check the TPS sensor also....

Will do

Pappy,
Compression all cylinders 100 to 102. With a little oil sprayed into cylinder, 110 all around.
Should this engine have oil injection?
There is a small solenoid on the starboard side of motor, mid-ship, that has 3 hoses that each run to top of carbs. There is a hose nozzle on the other side of this solenoid, with nothing connected to it.
We're learning a lot, but need a engine repair manual to help us with this project. Do you have a recommendation?
More questions, but we need to go step by step to see if it's worth repairing.
Thx!

What's the TPS sensor.

Disregard my question on small solenoid. I found out that's the fuel enrichment pump.
Found the ser.# it's a 1996 manufactured.
The engine was cold when we did compression check.
Thx!