1988 Johnson 70hp inspection

[cesandroid]

Howdy everone. Got a 1988 70hp that seemed to be running good other than possible 2 cylinders on idle but more specifically at top end was getting 38mph but now 32 with gps rpm 5400 rebuit 13.25x17 prop. havent gone into depth yet but thought i would the take head off and see. Firstly compression 1-127 2-117 3-117 cold, throttle closed. hmm i can see in the pictures why 1 is higher i believe. Bottom 2 bit of scoring on exhaust but no finger nail catching. unburned fuel on pistons and rebuilt whenever that was with 2 over on the pistons. new to me. Just getting thoughts on the pictures. plugs looked dark and kinda wet as well. Thanks

 

[racerone]

Motor has to come apart.----Does hose for the tell tale come off the side of the block or the top?

 

[cesandroid]

Top

 

[racerone]

Cooling mod was done.-----Motor will run , but I would take it apart.

 

[Crosbyman]

from chat gpt.. some don't like SEAFOAM some love it...Merc engine tuner seems good to

 

[cyclops222]

Time for a resurfacing of the block & cylinder head. Possible careful small SS wire wheel to clean piston heads. Very doable.

 

[racerone]

There are score marks on the cylinder walls.----Pistons are likely scored as well.----This motor can / will run.-----But it should be taken apart for proper repairs.----Little bit of carbon on pistons is normal and causes no harm.

 

[cesandroid]

Appreciate the feedback. It does run alright but could be better. I think Ill take on racerone's idea and open it up. Is there a recommended piston for this motor?

 

[racerone]

Post pictures of pistons after you open it up.----Need to try and determine what happened.