I don't know why, but I wouldn't doubt Kurt (Biggus). He knows his stuff.

I have a used TB IV distributor, with a new cap and rotor, and a TBIV V8-22 module, that provides 22* of advance. Let me know if you want em.

There are 2 22* modules. One gives 22* by 3500rpms and the other 4500rpms.

For an other than stock engine with upgraded cam, I would either get a V6 module or an HP module. It will allow more initial timing and help with idle quality.

Thanks for the lessons. How do I tell the difference between modules, which one gives the advance earlier? I'd prefer that one.

My motor (5.7L, 350 Vortec Roller) is using the largest recommended Crane marine roller cam 109831 (HR-284-2S-12 IG), Edelbrock 750 carb, Edelbrock air gap Performer RPM, Vortec heads with guides cut down for increased lift, Crane recommended springs, full roller stainless Comp Cams rocker arms, aluminum GLM manifolds, thru-hull 4" exhaust. Short block is stock, but fairly high compression from 99' Vortec truck (9.5 or 10:1 if I remember right). Freshly re-ring, HV oil pump (I regret this).

This in a 1984 17' Formula, which originally had a 4.3L V6 4 barrel in it (did 50mph as tired as it was with a 25P prop).

I have so far not purchased any. Had Mallory Pro-Comp 9000 magnetic, but it has failed twice. Once just by leaving the key on! I would prefer to get one soon, and one with a V8-24 module with early advance curve to help the cam, which is a bit large, but pulls great over 4000rpm. Boat is now running over 65mph with V6 1.84 raitio and 25P @ 5700rpm, I have not had time yet to switch to 1.5 ratio.

When I start it at the launch, people come running and asking what is in it. I tell them it is a 4 cylinder, running on 3.

Those who have it for sale, please let me know or PM me. Thanks again.

The V6-14 module gives only about 10 degrees of advance because it "thinks" it's firing 6 cylinders, not 8. It determines rpm and degree advance by counting firing pulses. It also cause the ignition curve to shft to the lower rpm range.
If you get one, set your total timing at 3000rpm and dont wory about the initial. Total should be around 34 degrees depending on the engine build.
The other modules:
V8-22, 22 degrees advance in by 3400 rpm
V8-22A 22 degrees by 4400 rpm
V8-24S 24 degrees by 44000, but 20 of that is in by 2000rpm
V8-24 24 degrees by 3700rpm
V8-20R 20 degrees by 5000 rpm
These are all from Mercs manual.
Gary

The V8-HP module gives 20* advance and all in by 3000rpms.

Super information, thank you. I'm looking to have it all in under 4000rpm, the boat is very light so risk of knock is virtually zero. Now just need to find one used !!!

As an added note, I installed a nitrous oxide RPM switch to add a third mode of my exhauts diverters. No, I can switch them ope, closed, or automatically open above a set RPM.