Control cable mercury 1983 70HP 3CYL

[TONYMURRAY]

Can anyone help? i have recently put a recon engine on my boat, and having lots of trouble setting the gear shift cable, i have taken it out in the water a few times and all works fine until mid rev range when at this point the engine starts bucking violently, when i back off the revs it runs fine.
It all worked perfect on the donor boat, i have adjusted the cable a couple of times myself but im not sure if there is a marker the cable should be set too.
Thanks tony.


any one out there with ideas?