merc 4.3 not running at full RPM

[springer07]

I am new to the site and hope someone can help me out. I have an 89 cheetah boat with a 4.3 mercrusier. When I bought the boat it ran really well. RPM's where about 4200 to 4500 I can remember exactlly. The Problem I am having now is that it will go to about 3000 RPM's really quick and it takes along time to get to about 4000. I have changed nothing(Prop, wieght,ect).
I have changed plugs, coil, new battery, timing set, lower unit oil, engineoil, new alternator, all new wirering(batt terminals and all the wires that run to the key switch to make sure I had correct voltage a the coil which I do).
If I try to ski behind the boat it takes along time get on plane and it never used to be that way. I have taken it to several places in my area and nothing they have done seem to work. The only thing that has not been replaced is the thunderbolt ignition modual I dont now if that would cause my problem or not Please help thanks

 

[Coors]

Re: merc 4.3 not running at full RPM

Did you change fuel filters?

 

[Apocalypso]

Re: merc 4.3 not running at full RPM

I had a similar problem with my 4.3 when it was about five years old. Turns out it was the power valve in the carburetor. The mechanic at the marina showed me a neat trick to determine if the porblem is a fuel delivery issue. Hove someone drive the boat up to the point where it starts to bog down and then slowly close the choke. If the boat speeds up then it is starving for fuel. My problem went away after I rebuilt the carb which included replacing the power valve.
HTH, Jim