Just wondering if I can do a compression test on a 1975 evinrude 40hp model 40555C while I have the lower unit off. I can't see any harm in it myself, but thought I would ask the pros. I want to know if the motor has good compression before I buy the water pump kit for no reason. You see, I found out that this motor came from a junk yard, and I am wondering why it was there. It runs good, but doesn't pump water. Well I took the lower unit off and found the impellor in pieces, but I want to know the compression before I go and get too far ahead of myself
I have always been told that a second of running the impellor dry would not only ruin it but the water pump as well. I realize that the plugs are all out, and the motor doesnt actually fire when testing, but does that do damage?? I always put my muffs on when testing, superstition?, i dont know. Another reason i do this is because i bring my motor to operating temps when testing, so the muffs are already on anyways, I created my benchmark at operating temp, so i try to compare at the same temp. I realize I havent answered your question, but Im sure you will get many valued opinions.