So we really do not know if it is really the original carburetor for that year ? How do we determine what model that carburetor is with out some identification numbers ?
Seafoam is a SLOW acting solvent. It does not suddenly dissolve all the crud at once and block tiny fuel passages.
I use it 1 time about each year to regain the lost mileage do to crummier modern gasoline.
Just fully tilt it up and lock it there. Transom straps to trailer.
Bow winched tight and safety chain snug.
I know. I have the only good boat that Lowe ever built.
Todays oils are fantastic compared to any older oils. EPA super lean burning cylinders demand the best under the WORST conditions. Turbos on most engines send temperatures up a lot when flored to pass or towing up long hills.