compression help on johnson v4 needed

[crankbait cowboy]

long story shrt, i have a 1973 johnson v4 115 horse i am in process of getting running. last dec checked compression in 20 below weather and got 95 psi on 3 cylinders and 85 on other. this engine had been sitting idle for years.i had fog oiled carbs and cylinder holes a bit , held carbs wide open,and all plugs out . it was cold and cranking was not great so i felt i would get better numbers with better weather for cranking and engine a bit looser. well tonight i tried again and am a bit befuddled. i did everything exactly the same and my numbers now are 75 on 3 and 50 on other.
3 questions, any ideas as to why my numbers fell off ( all i can think of , is poor battery cables, but they are same as ones used before) am i doing something wrong? and probably most importantly these latest numbers are below acceptable aren't they? any input would be greatly appreciated and thanks

 

[boobie]

Re: compression help on johnson v4 needed

Make sure it's spinning over fast enough and you may want to try a different compression gauge.

 

[racerone]

Re: compression help on johnson v4 needed

Pull the bypass cover on the low cylinder and have a look at the piston and rings.----6 small bolts and a 99 cent gasket.

 

[emdsapmgr]

Re: compression help on johnson v4 needed

Any additional oil, or lubricant added to the cylinders will affect compression-for a while. For instance, if the engine was fogged during annual winterizing, this gooey oil will serve to increase compression as long as there is residue still clinging to the cyl walls. That oil will gradually dissipate and when it does, the engine's compression will return to it's "normal" compression readings. Especially, once fuel/oil mixture flows thru the carbs, it will increase the dissolving of that fogging oil, effectively washing the cyl walls and returning compression to what would be it's "normal" compression. So, the earlier (higher) compression is probably an anomaly and wont' be repeated. The lower compression is probably that engine's "normal" compression. Normal compression on that engine should be at least 125 lbs per cyl. So, yours is really low. You may want to pull the heads and see if the seal rings are shot on the head gaskets (leaking compression.) That would be a best-case (cheapest/easiest) scenario.

 

[boobie]

Re: compression help on johnson v4 needed

Have you had it running yet ?? Try that before you pull the heads.