Compression values for 1964 75hp starflite

[JB]

Re: Compression values for 1964 75hp starflite

You keep insisting that an engine that compresses all 4 in a 10% span needs to be torn down. (The 4th cylinder was 50psi).

It is clear that the test was done improperly, accounting for the low numbers, and it is clear that the engine runs. There are a thousand things that can give a neophyte operator the feeling that an engine is low on power. Without hard numbers that feeling is meaningless. Same for the "feeling" that it is hard to start.

With respect, he doesn't have a clue how the engine works and you want him to tear it down.

I'm sure as heck glad my heart surgeon doesn't think like that.

 

[Monte1961]

Re: Compression values for 1964 75hp starflite

Hey guys, got a quick question for you. What should the compression be on a 1964 75hp evinrude starflite?

I just did the test and got some low values, 55 55 55 50(on cylinder 2). Are these values ok or are they too low?

Thanks.

Lets see if I understand this right heryg2711. These values on compression test correct? Also with 3 spark-plugs remaining installed right? To me looking at them, they are within the 10% +/- rule! Now you say with the spark-plugs uninstalled your compression values dropped to like 35psi? Not possible!!!!! Either you are not reading the gauge right or gauge is faulty. My suggestion is go to the store and buy a quality compression gauge and follow the directions on the package on how to use it! Also make sure battery if fully charged and no spark-plugs installed. Spray some oil in to cylinders and spin it over for about 3 to 5 seconds to coat rings and cylinders. Now recheck all four again by turning engine over 3 to 5 seconds on each cylinder. Repost your results of compression test. At this point, we can better understand the condition of yer engine and make educated suggestions on where to lead you. JB in my opinion is right on the money with the fact that the motor supposedly runs? Therefore no need to rip the head off at this time. There are to many indications that say OP. and or gauge are not preforming correctly and this alone needs to be answered first! Good luck and welcome to iboats.

 

[BonairII]

Re: Compression values for 1964 75hp starflite

I vote for getting a new gauge.

 

[aerobat]

Re: Compression values for 1964 75hp starflite

did you made the test with open throttle? i think for a 1964 engine every compression where the engine runs is good compression and there is no need to pull the heads off and risk to break the bolts or something other . when the engine misfires sometimes- let it misfire. man- this thing is more than 45 years old !

 

[wilde1j]

Re: Compression values for 1964 75hp starflite

No need for full throttle with a 2s motor.

 

[heryrg2711]

Re: Compression values for 1964 75hp starflite

Hey guys, sorry for the absence, been busy.

Quick question regarding compression:
How much of a difference in values will one see if the engine is not warmed up?
I think that's the blunder that caused this stir

Right now, i'm adjusting the timing. I got a new belt and adjusting breaker points. Belt's already in now it's time for the points.
After that, i will try to do the compression again, this time properly.