D.U.I Ignition timing question

With your initial at about 10 degrees the engine should fire easily.

The sticker was for the ProTec system which controlled timing electronically and could do things electronically like give you a certain amount of advance at any speed and load based on inputs to the computer  and make an advance curve that a set of flyweights and springs can't duplicate.

DUI says it has 24 degrees of advance on top of your initial setting. People around here seem to get somewhere between 20 and 24 when they check it.

Not knowing what your gas is like over there, 10 to 12 at idle is a good starting point

If you watch your timing marks as you raise the RPM you should see a nice advance curve that is smooth and does the exact same thing every time you raise the RPM's.   As noted the DUI may show you advance total between 20 and 24*.   You need to know what you are getting to get the best performance.  

As you watch the timing advance pay attention to the RPM.  Somewhere between 2,800 and 4,000 it will stop advancing and your timing will stay the same as you raise the RPM higher.  Most refer to this number as Total Advance.   So once you know your total and at what RPM it is fully advanced you can tune your base timing setting.   If as mentioned you get 20 or 24* advance and you want 32-36* Total you determine your base timing from the difference.   If you want 36* Total, and the distributor gives you 24* advance at 3,200 you would set your idle at 12*.  12 + 24 = 36 Total, and you are good as long as the boat runs well at 12* at idle.  The Total advance # and a smooth advance curve gives you your best performance and power, the base timing # really only affects your idle   Having too much Total timing will move you into detonation and that can rob power or damage an engine so don't get carried away.  If it runs outstanding at 34, great, if you try 36 and it starts to ping or the power lays down at top speed back it off.  There is no perfect number for all 351W engines, your compression, fuel quality, Octane, fuel mix, Lean or rich, all affect how much timing your 351W will run best at.