1989 Evinrude 110 hp

[crestlinermusky]

I picked up a 1989 Evinrude 110 hp with VRO oil injection system on it
Cylinder # 4 has 25 lbs of compression on it, the other three are 120 lbs
some one told me to check the compression by putting oil in the #4 Cylinder
If the compression reading changed (went up), it probably needs a ring job
If the reading did not change, it could be the head gasket
So,I tried putting oil in the # 4 cyl , nothing changed, still 25 lbs of compression
Has anyone heard of this method and does it hold any validity before I tear it down to see.

Any insight would be appreciated

Mark

 

[racerone]

Just pull the cylinder head off.----------Likely the damage will be obvious.--------Broken rings are very, very , very common on these engines.

 

[henleyhale]

the good news is, rebuiliding the motor isn't too scary, we are talking 600 bucks to put in new seals and new piston and rings and to have a machinist, bore over your bad cylinder, will take you 2 weekends tops if you work quick and dont put it off. I put my engine on my wifes kitchen table once and rebuilt it......... I DONT reccomend that, but I rebuilt it in the AC. alot of guys will say bore it all over or re sleeve the bad cylinder, thats for your pocket book to decide, but they are right, it will run best if all displacement is even. if you got lucky and its just a small scratch theres nothing wrong with just breaking the glaze and putting in new rings all around, check your other pistons retainer pin while your there if they are pushed in replace them or youll be back on the kitchen table quick.

 

[emdsapmgr]

Squirting oil into a cyl prior to checking compression may temporarily increase compression a little. As the engine continues to crank, the oil dissipates and you will soon see the original poor compression numbers. So the oiled compression number are meaningless. The best case scenario is that the head gasket seal ring is bad on once cyl. You'll need to pull the head to replace it. Once you get the head off you can inspect for any real damage-like a broken top piston ring.