Switching from Thunderbolt V, to Thunderbolt IV, which module would be best?
 

I have a 1997 Mercruiser 5.7 that started out as a 2bbl, with standard style heads and a 1.62 gear ratio, and thunderbolt V with a 4200-460 rpm range, and no knock sensor. Built a new engine, basically stock style bottom end, with modified vortec heads, 600cfm Edelbrock carb, Edelbrock RPM AirGap manifold, and a Howards cam with .495/500 lift, and 217/225 [email protected]. Cam rpm range is 1300-5500. Installed the engine, and the boat pulls like an animal until it hits the rev limiter at 4750rpm. Wanting to get away from thunderbolt V, and go to a tbolt Iv system without a rev limiter. Which ignition module would be the best? Camshaft company is looking for 32-34 full advance. Should I use the standard tbolt IV v8-24 module, and set it at 8-10 base timing? Or would there be a better module to use with it? Looks like there are many v8 module options. Thanks in advance.

1997 Larson 206 SEI, 5.7, Mercruiser alpha one Gen2

I would go with the EST or the DUI

I'd just go with the stock v8-24 module. Check your timing at full advance though after setting initial. Never trust what something electronic is suppose to do. Ran them for years on upgrade builds. If you had more cam a issues idling etc I'd maybe consider looking for the golden v6-14 module or what ever it is but your call. I'd stick with the std one.

The standard 24 degree advance module will work fine. The v6 module will allow about 16 to 18 degrees initial depending on your total which can clean up idle quality with bigger cams.

Or like AllDodge mentioned. I'm always in favor in HEI/DUI when applicable. I kinda thought you maybe already had your replacement tblV. You can get a pertronix for under 260.00 and comes with extra springs etc to Taylor advance curve to your needs. Either way get that rev limiter off. Lol

24* module with 8* initial. Always verify with timing light, as mentioned. A billion of sbc's are running a similar cam with that module.

Thanks guys. Just bought a v8-24 from a member here. Already found the correct harness locally. Looking forward to seeing how it does without the limiter. Thanks again