I have a fresh 454/365 mag in my 26 scarab/alpha with a 19" 3blade prop. Mods are a 420 cam, and fast glass risers. Initial timing is set at 8, and total advance at 3500 is only about 24 deg including the inital. Im only seeing about 4200 wot, and the engine runs strong to that point. Cam timing was set to 0. Throttle plates are wide open and there is no flattening at the top. Is it possible that the 24 deg module is not allowing full advance? Local service tech has told me that the modules either give full advance or not at all when bad, and that there is no partial. Also, on a 87, is there a rev limiter?

what would be expected that this might turn for revs with this prop and everything functioning ok?

No rev limiter.

Total advance would be 8 + 24 +32 assuming the module is a 24. Simple to check with a timing light.

Last the boat should be turning more rpms than that.

checked it with the light and Im only seeing 24 total. Can modules fail with only partial advance?

Full timing on a V8-24* module does not come in until closer to 3700rpms, but thats only about 1-2 mre degrees of advance. If you have a different module, it could come in higher or lower depending on what you have.

its a 24 degree module

1) try a different timing light
2) try a different module
3) rev it to at least 3700 rpm, set total advance, dont worry about initial