Looking for timing specs and the proper module number for carbed HP-500's with Thunderbolt-4 ignition. It appears there may be 2 diff modules in now with diff curves, but same total advance.

Help would be greatly appreciated.

If you got to www.mercruiserparts.com you can look up the engine by serial # and check to which module was used on it. I think it should be the HP module with 20* of advance.

These are re-man'ed engines so there are no serial numbers. They're Gen- 5 which pust them at about 90-95 vintage with Thubderbolt 4 ignition..

The TB IV ignition amp for the gen V HP500 merc part # 17316A1
is different then the TB IV ignition amp for the gen V 454/502 merc part #15248A1

Also the really early Gen V TB IV HP500 used 17316A2 but this was more like a big square box looks like a crane cap discharge thing , dif than the standard merc ignition amp on the triangular plate

Hey Ursus:

This is teh smaller type unit. So I assuming this woudl be the 17316A1? Any idea what the specs are?

Thanks

There are seven different modules available from Merc with advances that range from 14 deg. (used stock in V-6's but sometimes also in extreme hi-perf V-8's with idling problems) to 24 deg. The part you mention has a 20 deg. adv. With that one you would set the initial timing at 14 deg. adv to give you 34 deg. final at 3000 rpm. All pt.#'s and detailed info in Dennis Moore's "BIG BLOCK CHEVY MARINE PERFORMANCE" Hope this helps more than it confuses. --- Jer