Port side engine won't advance past 1800rpm

Took my 1966 Californian out today anticipating a good run on flat seas to "Blow" her out. Got to the end of the jetty and started advancing the throttles. She has twin early carburated 350's. Starboard advanced fine. Port side would not advance past 1800/1900 rpm. It felt as if someone was holding the propeller. The engine just felt bound up. Pushing the throttle past 1800rpms would only generate a notable resistance and a rumbling/vibration type of sensation. With the transmission out of gear the engine freely rev's as high as you want to push the throttle. Tranny problem? Older Velvet Drive model 71 I believe. Never experienced this before.
Thanks
Jim

I would probably start with pulling the plugs to see what they look like. It would be an obvious indicator as to running rich or lean. Rich would probably be more noticeable with smoke and smell. What type of fuel setup does this have? Change filters to see if you get a noticeable improvement.

Possibly something drifted in and fouled the prop? net? rope? even a kelp ball?
Ted

First things first, check for prop fouling. A plastic bag, rope or similar will do that.

If the engine is fitted with a 4bbl carb , some open the secondaries with a vacuum method.

Could just be the secondarys are not being opened.

check prop, check prop, check prop

Will swap carburetors between port and starboard engines. Will change out fuel filters and check counter weights in the distributor. Test run will have to wait until Sunday.

Swapped carbs between engines. Replace fuel filters. Fair amount of water. Bad gas around here lately. Test run this morning. Ran flawless 2700rpm 23knots, 19 mile round trip run.

Sounds like you got it

Jclays glad to hear you had a good run

Bad gas around here lately

NOPE!

Bad gas is the result federal requirement to dump ethanol in the fuel.

It picks moisture out of the air in your fuel tank, as well as reducing mileage by its content percentage.

Solution is to store with bare minimum fuel in tank , and fill the tank at the first boating outing.