About the only thing that can go wrong is the fuel pump diaphragm.----I have about 6 diaphragms on hand to repair that simple little pump.-----I would never buy a new big $$ pump.-----And no I would not use an " amazon special " on these wonderful motors.
Just solved an Evinrude 15 HP.-----Stalling repeatedly.------Before even looking at the motor I looked INSIDE the fuel tank.-----Pick-up hose on a cheap plastic tanh was loose and sucking air.----Easy fix.
Step # 1 is to use a 50:1 ratio.------Ignore that 100:1 sticker.----Pull it off and throw it in the garbage !!----Factory bulletin came out many years ago on that issue.----I think throttle plate is opening too soon.-----Post video of it idling at slowest speed for 20 seconds.
The EVINRUDE is a smooth runner if in good condition.------One issue with them is a weak head gasket when new.-----Replacement gasket ( SIERRA ) is improved with metal rings.-----May need to adjust slow speed mixture.-----I own many of these 6 HP models ( 66 to 79 ) and they are fantastic...
???-----The boat moving on the water is the LOAD on the motor.------Your motor produces POWER to match the load.----At 3800 RPM your motor is NOT producing 60 HP.-----There for you have to reduce pitch to get motor running at higher RPM.-----Try a 9" pitch and see what RPM you get.
Old time fish finder.------Old timer told me he would go to the lake.-----Watch for " active seagulls " diving on the shoals.------Minnows on / near the surface means big fish in the area.-----Time to launch the boat.
The different fuel pump was used on many other motors before 87.-----Those simple pumps are often replaced when nothing really goes wrong with them.-----Other than a new diaphragm one every 15 years or so.