Mercruiser Thunderbolt IV Ignition Module
#13
The V8-22(second column) would be my second choice and then V8-24 closely behind it.
Its nice to be able to run a little more initial timing to smooth out idle.
The V8-24 will still work fine in most cases though and was probably used the most by Merc.
Its nice to be able to run a little more initial timing to smooth out idle.
The V8-24 will still work fine in most cases though and was probably used the most by Merc.
#14
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Joined: Nov 2004
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From: On A Dirt Floor
Absolutely surprising what just an extra 2*-4* of idle can make on some motors with a little extra cam and/or aluminum heads have, especially for cold start. Typically makes non choked carbs start easy too.
#18
#19
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From: Lake Ozark, MO USA
Sorry, I have not been keeping up with my own post. Been busy fixing house issues, hot water tanks and humidifier. Hot water tanks done for now and parts on order for the Humidifier. Here are my thought on the timing for my particular set up. Engines are bone stock 502Mags with QJ Carbs. I am running 34 degree total timing with the stock 20 degree modules. Issue I see is that these are not full in until 5000RPM. Original thinking by Mercruiser back in the day was these engines have to run everywhere and good gas was sparce and engine life could be reduced with crappy gas and tooo much timing. I am not concerned with the gas issue. I run clean gas with no alcohol and usually higher than 87 octane. Never had issues with fuel, so that is out of the equation. I have so much initial advance, that engines crank hard and slow when warmed up. I also am wanting to see how engines will work with all in advance at a lower RPM.
#20
What is your normal cruise RPM now? Would be curious to see what your EGT's are currently at normal cruise speed. Since you are bone stock the 24's should work out well for you with taking some initial timing back out.





