Wrong Carburetor?

[rolmops]

1984 rebuilt 3 liter 140 Mercruiser with EST Voyager ignition
After rebuilding, this engine runs fine and smooth but still does not want to go over 3200 rpm while pushing a 1984 Starcraft Islander with a 14.5x 19 prop when it is properly trimmed out.
Trying to find the problem,I discovered that the carburetor on the engine #1389-9564 is for 165 and 170hp engines. The carb that is supposed to be on these 140 engines is #1389-9350 or #1389-9562.
Can this wrong carburetor cause the low performance? If it does,should I replace it with a #1389-9350 or a #13899562?
Thank you for your advice and opinions,
Cornelis.

 

[NHGuy]

Did that carb & prop run the boat previously?

 

[rolmops]

The prop is original,but the carburetor was installed after I found that the original one was leaking because of bad screw threads.I was told that this was the right carburetor. This was before I ever did run the engine. I never got it to run over 3000 rpm.

 

[rolmops]

I just found out that the 165 engine is 3.7 liter where as mine is only a 3 liter. So it is probably a good idea to change out carburetors

 

[Walt T]

That is not the cause of your low power assuming it runs okay otherwise. Check:
Throttle plates opening all the way
Ignition timing
condition of ignition components
Exhaust shutter not damaged
correct prop
Hull condition

Thats just for starters Dont assume the carb is causing this without checking everything else first

 

[rolmops]

The throttle plates are wide open,ignition timing is at 1atdc with shunt 23 btdc at 3400 rpm and 24 btdc at 4400 rpm,ignition components and alternator are new ( one month old) and in good working condition.prop is what this setup calls for and is brand new without dings.
Hull is good,this is a trailer boat.
I never did see an exhaust shutter in this engine.
I just did adjust the linkage a bit. I'll see if that helps.
Thank you for the reminder that I should check things in a systematic manner and not just shoot from the hip.

 

[tinkerguy70]

I just found out that the 165 engine is 3.7 liter where as mine is only a 3 liter. So it is probably a good idea to change out carburetors

I am certain that is not your problem.
I have the exact same year 3.0, and for reasons I would bore you with, I rebuilt and used one I had from a 3.7 (470) mercruiser. It is a GM rochester 2bbl, the original was a mercarb.
That carburetor has been performing perfectly since the day it was all dialed in and adjusted. That was over 3 years ago. Those carburetors are so similar, you could almost use the same rebuild kit (but you can't, I said almost).
I think you have problems other than the make of the carburetor. It could have some issues and need a good rebuild by somebody that knows what they are doing, or it could be something totally unrelated.
If the engine is running smoothly other than not reaching WOT RPM, I would say go with Walt T's suggestions.