1981 Mercury 25hp No Top end power

[Kawaiikeno]

On the way in from fishing the 1981 Mercury 25hp suddenly started to run very badly above 1/2 throttle at first I thought it just fouled a plug But it didn't.
So far I've installed new plugs cleaned the coil terminals cleaned the carburetor and fuel pump and replaced all the gaskets changed the fuel lines and verified everything is assembled correctly. less than 10 hrs. before that it had a new CDI (switch box) and water pump installed.
It starts and idles perfect runs great until just past 1/2 throttle then it falls flat on its face.
Carburetor is a BC 1B and the only thing I can find is there is no #32 a Jet, the exploded view doesn't show where it goes. Directly opposite the slow jet is a threaded hole with nothing in it. I thought the #32 jet might have gone there so I ordered one but it won't thread in.
Any help would be Greatly Appreciated!
Thanks Mike

 

[Scott Danforth]

compression?

my first thought is go back to the carb

 

[Calebwitdafro]

If this is a two stroke, inspect the reeds by opening the throttle plates. Does the primer ball stay hard? Is your throttle linkage in sync? With the engine in idle, spray a little brake cleaner around the engine and listen for it to bog down. Around the intake, carbs, and the power head. You might be sucking a lot of air and don't realize it.

 

[Texasmark]

Does your engine have a fuel filter? Since you redid your plumbing, you may have included that. Otherwise, a clogged filter will give you those symptoms.

 

[Kawaiikeno]

Thanks for the replies
It is a two stroke single carb
It has within a pound or two of 125psi on both cylinders.
The reeds are not visible without removing the carb and plate.
I do not believe the throttle is in sync.
I have sprayed carb cleaner around everywhere a leak could be (case halves, reed plate, carb base gasket only place I didn't is crank seals only because I couldn't get at them.
The fuel filter is not plugged and is now always full.
Because of the way it acts ( Runs perfect until a certain rpm / throttle position) I do not believe it is starving for fuel if anything it acts like its going way rich as in pulling the choke out.
That is why I keep going back to the carb, on the right side of the throttle bore at 2 O clock is the idle screw directly opposite at 10 O clock is a identical hole that goes to the other side of the metering chamber that has nothing in it.
The exploded views of the carb show a #32 it is a Jet , The carb I have does not have this jet anywhere and the exploded view doesn't show where it goes so I bought one but it will not thread into the hole
Thanks Mike

 

[flyingscott]

Do a compression and spark test.