Popping Sound from throttle body

today I ran down to fuel up. I ran on plane for a short while without issue. Trolled for about 20 mins to the fuel dock and fueled up. I added additives to the fuel before leaving the fuel dock and then I trolled for another 20 mins before I jumped back on plane. When I tried to get on place I heard what sounds like popping coming from my port engine. Limped back home and did some testing. The engine. accelerates fine slow up to 3400 rpms when not in gear. If I rev it quickly up to 3k rpms it pops, But when under load as stated there are a constant series of pops along with loss of power. Planning to check plugs and wires tomorrow. Also note I replaced risers and cool fuel modules this spring. I took it for a shake down cruise after and it performed fine. I ran on plane for about 30-34 mins.

I don’t think it the fuel as the other engine runs fine.

I had a similar issue at the end of last year.
2007 350 MAG with 300 hours.
It still had the original cap and rotor. I replaced them both with mercruiser OEM parts and it cured the popping/misfiring and loss of power.

Sounds like a possible lean fuel condition. Be careful as you can do serious engine damage....as in a hole in the piston.

Pulled the plugs and it was definitely running lean. I swapped the cool fuel module with the starboard engine and it runs much better in neutral. So it seems it could be the low pressure pump. Will take it for a ride and see how it performs under load.

So it turned out a low pressure pump was the issue. Since i wanted to get back up and running I just purchased and replaced the CF3 the same day as my local marine shop had one in stock. I'm going to see if i can pick up a low pressure pump and rebuild the unit as a spare.

CF3 units have known issues with paint delamination on 8.1s and maybe it's the same with yours. Mercruiser had a TSB out for a series of motors where they'll provide the parts for free and you pay the labor to install. You'll get the CF3 unit, fuel rail and new injectors.

If one has failed then more than likely the other won't be too far behind.