You mean mechanical advance and virtually all distributors are. What have you got now?  MSD makes a nice piece in the ready to run version.
A vacuum advance can be locked out.

Well, let me ask this first.

What do you think it will do?  When an engine takes advantage of vacuum advace, it is under part throttle at a light engine load with high manifold vacuum.

I have never had a boat do that.

A boat engine (especially a jet boat) has a linear torque curve and does not have to "pull a gear".

Love to hear more discussion on the matter,  I'm bored as shit.

Speaking specifically car.

The vacuum advance is attached to a ported vacuum signal on a carburetor,  this port only has manifold vacuum above idle. On a high performance car,  the vacuum advace will be hooked to manifold vacuum,  this will actually "retard" the timing under heavy acceleration and in my personal opinion, making the term "vacuum advance" somewhat backwards.

On the jet boat engine, the vacuum advance can never really amount to any real performance or economy gains. Mainly because the conditions that make it work happen virtually never. You could argue that it will improve part throttle running efficiency, but mechanically advancing the timing for all in early sort of does the same thing.


Add to that that there is no such thing as a marine approved vacuum advance distributor,  then I guess it would make the argument moot.

GT