What ignition system do you have.If you did not dyno the motor the only way to tell what the motor likes for base is to take the boat out and have a friend drive,have him put it in gear and idle around while you advance the distributor and watch the vaccum gage and look for the highest vaccum,then lock it down and look at it with a timming light,when done return the timming back to the 12* and tell me what you found.My motor liked 38*but since I was allready running a thunderbolt IV system I went with the V6 module which gives me 10* of advance and I run 24* base.Also make shure the you are not on the timed port when you hook up the vaccum gage.

For the record Berry Grant carbs you divide in half the vacuum reading for the power valve Holly is the one that you step down 2

Thanks for the help / it hard learing carbs even more on the water..... Well I ran in the sunsation run today and the boat did good. Ran WOT for over an hour (had to keep up) LOL But still some tuning needed....

What Ing.system are you running.

Go to junk yard , buy a HEI and run with it and save they work great. Ran one for years and carried a spair coil pack.