Thanks TJ,
If I understand you correctly, I think I'm looking at it the same way. The motor as it is now, N/A, I run 36 degrees in full by 3200 rpm so I'm assuming that if I see the same MAP at 3500 rpm as I do now (I'm sure it will be a little different) I should be able to safely run the same timing.
The ECU will read and adjust timing by what the pressure/vacuum is in the manifold so maybe something like -3 @ 3500 rpm will get 35 degrees, 0 @ 3500 will get 32 degrees and +3 will get 30 degrees.
Hmmmm?
What do you think?
Dave

That makes sense, Im interested in that FAST system also. Does that ecu have the knock sensor? You might want to sneak up on the retard slowley so you cant feel it happening. Greg

The turbo motor I had I had a hobbs pressure switch plumbed to the intake manifold. When the intake saw boost the switch would close thus causing my MSD retart to back the timing off. Motor has so much toque at that point I never felt the timming being backed off.

As far as what you are seeing now with your N/A motor will be different after blower if you are using RPM's as your refrence point. You will need to use your boat speed as refrence point. Remember you will be running a larger prop or gears so the motor is going to be loaded at a lower RPM than before. As engine RPM goes up the motor has less time to detonate. I would look at what your timing is now when motor is not under boost at the higher speeds & then back timing down a little from there to keep motor from detonating. I guess when you posted your question you should have asked not only vac/pressure but also speed at that RPM. If I am not mistaken at 3500 rpms I am running about 65 mph, 4k = 75 mph.

Great observation TJ.....bigger prop = more speed = more engine load at same rpm.
Guess I won't know until I'm sitting there with my laptop monitoring the real world readings (A/F, EGT, MAP, etc....)

HPJunkie, I did not upgrade to the knock sensor. I did upgrade to the wide band O2 sensor however.

Thanks,
Dave