85 horse johnson, bawgs down at open throttle

by Bob Stigall
(Muncie, IN)

I have a 69 Glastron fish/ski boat. It has a 85 horse johnson, that has always ran perfect for me since ive owned her.. (about two - three years).

Work that known that has been done. water pump went out, over headed melted one side of the head. Certified mechanic, (ivy tech teacher) rebuilt it. new water pump and head/pistons, etc. runs like a scalded dog for two years..

This past weekend, launched it. idles fine, runs fine, take off wide open throttle runs great. pulled a tube for about twenty min. then started bawging down... wide open throttle, used to get me about 5200 rpms, now when it bawgs down, 2000 rpms, thats it, feels like im going 10mph. I can put it back into neutral, runs fine. flip up the warm up fast idle, speeds up to 4000 rpms.. runs fine.. drop in gear, full throttle, bawwwwggg.. no power.

I made the few the same as always did.
I changed plugs, thinking fauled plug.. NOPE.
checked the fuel filter, (small screen) looks fine
ran it with the ear muffs on in my back yard for 20 min. ran fine..

my marina here is backed up, cant get it in for about three weeks.. Can anyone help me with some ideas to do, or maybe someone has had the same problem..

Thanks, Bob, Muncie, IN.