1970's Johnson 20

[b sullivan]

When Testing This Motor On The Boat It Would Not Pump Water Above Half Throttle, When Going Slow It Is Perfect. It Has A New Impellor , Housing Not To Bad.
Changed Both Again , Put In A Much Better Housing , Still The Same.
Confused ???, Any Help Would Be Appreciated.
Thanks In Advance, Dave

 

[F_R]

Re: 1970's Johnson 20

Is the screen in the leading edge of the exhaust outlet snout? Is the plug in the hole below the screen? Is the bypass plate in place on the side of the gearcase?