OMC 120hp timing specs needed

[Lgsr]

Can't locate the correct specs for timing my 120hp I/O. Not sure of exact year '71, '72 or '73.<br /><br />153 ci<br /><br />Any help?

 

[retodd]

Re: OMC 120hp timing specs needed

Its a GM block and the early mercruiser ones were to be set at 6 degrees.