Engine runs but has low power

[DCHunt]

We have a late model Atomic 4 in a Pearson 36 sailboat, built in 1972. We have only used it in fresh water (Lake Erie) and have maintained it over the years with parts from Moyer. About 5 years ago, we replaced the head gasket, cylinder head and exhaust manifold because of a crack in the cylinder head. It has run fine since until about 1/2 way through the summer when my brother was running it at speed and he heard a couple loud pops. After that, it will run but has low power.

I have replaced the spark plugs. The first two closest to the flywheel appear to have more carbon on them than they should. I checked compression and it is 75 to 80 psi in all four cylinders. A guy that knows a heck of a lot more about engines than me took a look at it and found that when it was running and he opened the throttle, it took 3 or 4 seconds or more for the engine to rev up. He thinks it may be a carburetor issue. We replaced the carburetor about 10 years ago.

What other things should/could I look at that would cause this low performance? I'm ready to order a new carburetor from Moyer but wanted to check to make sure there wasn't something else I was missing.

Thanks,

Dan