Soldier,
First off let me say a HUGE THANK YOU for serving our country! There are still some Americans who know how lucky they are to have brave men like yourself defending our country. Never forget the Vets!
I just want to chime in on your problem. I have the same engine with a Thunderbolt IV. Mine is a 1988. I thought for sure with your's being a 1995 it would have Thunderbolt V. But if you say it's IV, I believe you.
On your timing:
If you have a pointer (on block) and a V-groove/line (on balancer) then that is your 8 deg. In other words, that mark is not Zero. You want to time your engine so that when your timing light flashes, the mark on the balancer meets up with the pointer.
Don't try to set the timing to some imaginary 8 Deg. before the V-goove/line. The V-groove/line IS 8 Deg before top dead center. When setting ignition timing, Zero is useless. Zero is only used for mechanical timing of the Crank/Cam. They have to be set so Zero coincides with their operation.
You must have Advance in ignition timing. Do you know why? The expansion rate of the ignited air/fuel mixture is a constant. Engine RPM however is not. Even at idle the spark has to go off at 8 deg (or so) before top dead center in order for the expansion of the ignited air/fuel mixture to kernal into it's most powerful force. As engine RPM increases, the spark must fire sooner and sooner in the stroke to compensate for the piston moving faster and faster in the bore.
If you are getting any kind of popping and missing, you have something wrong. Get the ALT back on there and then do the following procedure. One thing before you do this. If you bought a SIERRA dizzy cap. Return it and get a real Merc Quicksilver unit. The SIERRA IS JUNK. It will throw the timing off because it's made poorly. Trust me!
1.Start the engine.
2. Forget timing lights and everything technical for right now
3. Loosen the distributor hold down clamp.
4. Turn the distributor counter clockwise until the idle settles down and the engine runs OK.
5. Let it run until it reaches operating temp.
6. Set the idle to the correct speed. On my 4.3, it's 650-700 RPM. DONT USE THE TACH AT THE HELM! Use a correct engine analizer from SEARS or where ever.
7. Once you have the engine running in the correct speed range, take out your timing light and point it at the balancer and the timing pointer.
8. You should be close to the correct timing. Now, from what perspective you look at the pointer can make a bit of a difference. I try to look down and from the right (port) side so that my eyes are in-line with the plane of the pointer.
9. Turn the Dist. base until the timing marks align. Hold here.
10. Check your engine RPM.......it changed didn't it? Reset the engine idle speed back to specs.
11. Check the timing again. Move the Dist. until it's back on the mark.
12. Follow steps 10-11 until you are within specs on both the idle and timing. Lock the dizzy down and check again. It can move.
One more thing. Merc. wants you to set timing so that the balancer mark is to the advance side of the pointer. (just a hair) This is negligible. On the mark to a hair before is fine. You will notice that the mark dances a bit with the flash anyway. This should just be a tiny amount, don't worry about it.
Now open her up to 2000 rpm for a few seconds. If you have no back firing/popping/missing, you have the engine timed correctly. You can also observe the advance when doing this. The timing mark will walk towards the Starboard side of the balancer.
I hope this helps. Thank you for your sevice to our country! Any more questions feel free to ask me.
Johnny.
