318 chryslers: rPM's dropped from 4500 to 3000 on starboard engine underload. engine will free rev. to 5500 and hold steady. When in gear the motor runs fine up to 3000 rpm's. Above that the engine acts as if its flooded. As soon as I drop back to 3000 rpm's the motor smooths out.. The carbs are 4 barrel. Carbs have not been rebuilt since late 90's. Do I have a diaphragm thats not functioning properly? Thank you in advance for any thought on this subject........slackard

Changed water/fuel seperator filters and fuel filters. Runs great. Planes off at 4000rpm-15 knots.Much more fun to troll and chase the salmon running up river.

First off 318 were rated 4000 to 4200 WOT.

Free reving over that can lead to very interesting and expensive noises so I would avoid that practice in the future.

1. You may have lost ignition advance

2. Carb problem

Suggestion: You can swap carbs in a half hour to see if problem moves. If it doesn't it's fuel supply or ignition related. Clean your filters.

Do you have points or electronic ignition. If points, and everything seems right swap out the resistor.

Make sure you back feed us what you find as we all can learn.