1988 johnson 120 powerhead removal

[muddyfishin]

ok so final have got the engine all back together this weekend and was able to get her started, seems to run a lot better than previous to the new rings, before the tear down it had 120 psi in all three except the top port side was under 90,, and it used to surge from 1500 to 2000 rpms at idle,, now that ive done one piston in that low cylinder due to blow by marks and rings all around,, before I started the motor its had low compression all the way around which scared the hell out of me,, so I decided to run it and hopefully get the rings worn in with the fresh honed walls. after idling for about 15 minutes I came across a problem with the killswitch not doing a damn thing and my black yellow wire seems fine, maybe the connection in the power pack is bad?? anyways I did a compression test after running and both starboard cylinders are at 120psi, the lower port is at 110psi (which was at 120psi before tear down) and the top port which was my trouble is at 100 now so the question isss,,, what the heck man lol expert advice appreciated

 

[racerone]

Putting new rings in worn out grooves is not a good idea.------Did you really , really look at the ring grooves with a magnifying glass or microscope ???-----I have done some and it is not a pretty sight.-----Did you measure the cylinder bores accurately with a bore gauge or good experienced hands with telescopic gauges ?

 

[muddyfishin]

I checked the cylinders with a bore gage and all seemed to be in spec and believe me I didn't just check once I went through all four multiple times as I was waiting for parts, I didn't look at the ring grooves under a scope or anything I did soak each piston in cleaner for about 3-4 days each and cleaned and visually inspected. that one cylinder got a new piston with rings and is still my lowest compression tho maybe there is a section of the bore slightly out of round I will say that one psiton was harder going in than the others until it got past the first inch of the cylinder opening

 

[Bosunsmate]

Remember to retorque it after its first heat cycle that youve just done, that may help with compression numbers
So you didnt replace that piston with the loose ring?
Hows it run on the water?

 

[muddyfishin]

when you say retorque are you referring to the heads? I should probably just retorque anything I can get to lol I only replaced the piston that had low comp, all the others seemed good after a few days soaking in parts cleaner and scrubbing all carbon build up away. haven't got to get it in water, I have to refoam the hull and do some fiber glass work then paint and then I can test run.. its going to be a busy month if I want to hit the water this season

 

[Bosunsmate]

Yep retorque what you can, id put her in before the paint if you are going to miss the season!

 

[muddyfishin]

sounds like a good plan. and yea ive just ordered all my glass and materials and should be good on time , really the season here just started and I dont quit until the water is locked up with ice! I think ill be out within a month if all goes smooth, river here is still flooded a bit so not missing too much action just yet, ill get back to ya when I get a chance to work on the engine again, im waiting for the gasket on the primer solenoid and probably the weekend to get done and run another test

 

[Bosunsmate]

Where do you live? Must be quite far north

 

[muddyfishin]

northeastern usa, in Connecticut. get the full range of seasons, seems the winter lasts the longest though haha