1999 volvo penta. 4.3

was boating and it was running great. all of a sudden it would not go past 2100 rpms. It has the old prestolite ignition module. I have changed the gas filter, carburetor, wires, plugs. compression check was good. engine only has 500 hours. set the timing and it really wasnt off. did all of this and it is still doing the same thing. starts right up, revs to full throttle. put it under load and wont go over 2100 rpm, is not missing or backfiring. if i keep try to give it gas and after about half throttle you can smell the gas. at witts end any help out there.

... and the distributor cap and rotor were last changed...? Cap and rotor are a change annually item for many engines. Check to see if advance weights in disti move freely.

I have a '96 4.3 and i don't think there is advance weights in that model?? I could be wrong?

No, you could be correct...I don't know off hand when change was made.