120 hp Evinrude 1989 runs good one day then not

[Steve135]

Hi, This is the third engine that doesn't have a plate or any other ID on it that I have worked on the past year. This motor runs perfect one day then not the next. Heres what I mean runs at 5800 rpms and the boat runs great. the next time I use it runs 3000 rpms max and can't get out of it own way! ok did all the checks and rebuilt carbs.The last day before pulling the boat out, the engine ran so good I was afraid to pull the motor off as I was going to swap it out for new motor. Heres what I have found on compression check 1,2,4 all about 125 # 3 was 0 I mean it was zero nothing! Now how is this possible if the boat ran perfect the day it came out. I mean the speed as checked by GPS was the same as it ever ran since I had the engine new? Ok the piston is moving I checked that. Does this mean its a hole? Never seen zero! <br />steve

 

[jy118lfd]

Re: 120 hp Evinrude 1989 runs good one day then not

Pull the head on the offending cylinder they come off very easy and that will tell the whole story. If the cylinder is really zero(gauge not wrong)you will most certianlly see the damage. Intermittent problem like you stated could not be compression though once the cylinder is at zero it will not come up at all. <br /><br />If you do not want to pull the head you could also get another gauge and test again?

 

[rodbolt]

Re: 120 hp Evinrude 1989 runs good one day then not

hello<br /> first determine if in fact one is zero. if it is its most likely rebuild time for the mechanical part. then you have to find out what killed the mechanical part of the motor. easyist way is to pull the head. does your alarm horn go beep when you turn the keyswitch on? when was the last oil tank cleaning if its still oil injected?after the mechanical part is repaired its imperitive to fix the subsystem that caused the piston failure.<br /> good luck and post back

 

[cbelgum]

Re: 120 hp Evinrude 1989 runs good one day then not

When you get the head off, have a look to see if the piston hasn't actually separated from the crown - I have exactly that problem on my Johnson 115 (1974)- and the engine still runs (ran) but it would explain a zero on the compression. Even with a hole in the crown you would see some pressure.<br /><br />Intrigued

 

[cbelgum]

Re: 120 hp Evinrude 1989 runs good one day then not

When you get the head off, have a look to see if the piston hasn't actually separated from the crown - I have exactly that problem on my Johnson 115 (1974)- and the engine still runs (ran) but it would explain a zero on the compression. Even with a hole in the crown you would see some pressure.<br /><br />Intrigued

 

[Steve135]

Re: 120 hp Evinrude 1989 runs good one day then not

Hi ok lessons learned, never believe the owner of the motor! I spent a little time and finnally removed the head even though the onwer asked me not too because of the expence of the head gasket if I were wrong! I first found the head gasket blown at that cylinder. This caused water to enter the cylinder,probally last season. This year on start up that cylinder was rusted from a poor winterizing. This alowed the rings to scar the cylinder as well as a chip off the piston to gauge the hell out of the pistion wall.Beyound repair! The combo of the these events lead to zero compression. Anybody needing 120 parts can email me at Nevetsd@aol.com