power problem on the water

[ahcliffsr1]

I have a problem with power when I put the boat on the water. It runs fine in the drum , but not under power on the water. It will start back up ok . It just won't run under pre***ure . I have serviced it , tuned it up , It has good compression , Any ideas ? 1976 Evinrude 35hp model # 35652S ser # E0001807. I've reached the point that I think I may need to start all over from scratch . Thanks for any help .

[JUST-IN-TIME]

did you check that timing is increasing?

what was compression