4.3L Mercruiser timing

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Pipster

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I have a distributor and coil, but have electronic ignition. Where does the shunt clip from and to when trying to make the electronic advance go to 'base' timing? What does a 'shunt' look like, and can I make one myself?
 

bjcsc

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Re: 4.3L Mercruiser timing

The shunt plugs into the ignition module. You'll see there's two sockets, one is used and one is covered. It plugs into the covered one. I think the pins are too close together to make your own, and they're cheap so it's not really worth it anyway. It looks like a plug with a loop and another wire...
 

Don S

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Re: 4.3L Mercruiser timing

I think the first thing one needs to know is what distributor you have, and what year?
The Thunderbolt IV or V doen't take a shunt at. The TB4 times like a point system, the TB5 has a method of putting into base timing, but it's not a shunt.
Only the EST distributor requires a shunt.
 

Pipster

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Re: 4.3L Mercruiser timing

It's a common looking 6 cylinder distributor like in a car. It has 2 wires coming out the front base-one white/green stripe and one white/orange stripe. On the back of the distributor is a mounted module with part # 807829-1 on it. It's about 2 1/2 " by 3 1/2 " by 1/2 " thick. It says 4.3LX/LXH Alpha on it. I believe it is an electronic advance system and the distributor has no points inside. I am not familiar with the Thunderbolt IV/V terminology. I hope this helps. Thanks.
 

Reel Poor

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Re: 4.3L Mercruiser timing

Could you post the engine serial number?
 

Reel Poor

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Re: 4.3L Mercruiser timing

TB520timing20instructions.png
 

Pipster

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Re: 4.3L Mercruiser timing

Thanks for that Reel Poor. Here are a couple of tidbits from Mercruiser Tech in Stillwater, OK I found. I hope it's ok that I post their # here. 405-743-6566
I spoke with a great guy named Brad and he shipped these items down to me lickity split. It really helped. I found the Purple/White wire at the bow/starboard of the engine just laying there waiting to be used! It had a female push plug attachment. I made a wire with a male push plug attachment/round hole connector and voila' that's all there was to it.
Got the timing set to 8 deg/BTDC, tightened the distributor and it was still right on 8 deg/BTDC. Thanks to you all for your help.
 

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Reel Poor

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Re: 4.3L Mercruiser timing

Not a problem but will have to pass on the thanks to Don S for originally posting the outline. :)
 

Pipster

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Re: 4.3L Mercruiser timing

Then my thanks to Don S as well. Cheers! Happy boating all.:p
 

Merc4ever

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Re: 4.3L Mercruiser timing

All well and good for the Thunderbolt V, but I have a Thunderbolt IV on a 1989 4.3 Mercruiser and I'm trying to time it right now and can't find how to put it into base timing mode. Service Manual doesn't mention it in the timing section and I read on Iboat forums that there is no purple wire on the Thunderbolt IV.
 

Don S

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Re: 4.3L Mercruiser timing

Start a new thread with your question. not a dozen posts in on someone elses 2 year old post.
 
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