Merc 4.3 timing Q

[Jacalore]

'96 engine, timing spec says 8 btdc. Owner says it's a thunderbird iv. No grounding necessary. Timing reads tdc. Changed it to 8, runs like Crap, no top end, backfires at low rpm. Somethingwrong here. Could owner be wrong about ignition id?

 

[Bt Doctur]

Re: Merc 4.3 timing Q

ThunderBolt IV no base timing wire, just point and shott with the timing light.Are you sure you hooked up to #1 plug wire?

 

[Jacalore]

Re: Merc 4.3 timing Q

Hooked up to wire labeled #1 on distributor cap. Arrow pointing away, towards plug.

 

[Jacalore]

Re: Merc 4.3 timing Q

I'm thinking maybe it's a T5? I'll try looking up the engine serial number.
Know of an ID photo somewhere on the web?
Thanks

 

[Fun Times]

Re: Merc 4.3 timing Q

I'm thinking maybe it's a T5? I'll try looking up the engine serial number.
Know of an ID photo somewhere on the web?
Thanks

Just Google search TB 4 then search TB 5, get to know what the ignition modules looks like and see what one you have.

Or post the engine serial number and we can tell you. 1996 most likely a TB 5 and needs grounding.

Good luck.

 

[Jacalore]

Re: Merc 4.3 timing Q

Engine #0F761165

 

[Jacalore]

Re: Merc 4.3 timing Q

Just Google search TB 4 then search TB 5, get to know what the ignition modules looks like and see what one you have.

Or post the engine serial number and we can tell you. 1996 most likely a TB 5 and needs grounding.

Good luck.

Not my boat, trying to help out a friend. I didn't take a photo of the distributor, but did grab the engine serial number: 0F761165

Any help appreciated. Thanks!

 

[Fun Times]

Re: Merc 4.3 timing Q

Engine #0F761165

Ok, this is very strange, your serial number comes up as a TB 5, but looking at your ignition module it shows it as a TB 4 both by looking at it and looking up the part number.:facepalm:

Engine comes up as an MERCRUISER TB5, W/PS, TWOPCEX, WORO 4.3LX ALPHA

MERCRUISER - (4.3LX H.P. (1996)
Serial No: 0F761165 Model No: 443L100JS

Here's the complete parts catalog for this serial number
http://www.mercruiserparts.com/selectDocs.asp?doc_nbr=801874+96

Ignition module item number 35,
http://www.mercruiserparts.com/Show...desc=WIRING+HARNESS+AND+ELECTRICAL+COMPONENTS

Your going to have to do my first suggestion to see what you really have or post a photo of the Ignition module.

Usually the TB 4 will say it on the front of the module while the TB 5 has a cigarette sized pack look to it that can be found on the 6'th photo down in the next link.

805361T1 | eBay

 

[Jacalore]

Re: Merc 4.3 timing Q

Thanks for that info. Ok, I'll have to get a pic of that module. Odd that both are listed for this engine... Maybe a crossover year, from 4 to 5?

Thanks again for your help.

 

[Bt Doctur]

Re: Merc 4.3 timing Q

assuming the dist was clocked correctly ,you can do it that way. If not, go to the #1 cylinder wire at the plug.#1 is port side ,very first one.

 

[Fun Times]

Re: Merc 4.3 timing Q

Maybe a crossover year, from 4 to 5?

Most likely!

 

[Jacalore]

Re: Merc 4.3 timing Q

If the Dist wires were mismatched, I would think the engine would not run smoothly. that's the thing, just wanted to check the timing, the engine is not running badly, just not optimal. But something is not right. Tdc is not correct, so I need to find where the error is... I'm leaning toward mis identification of the ig mod

 

[Bondo]

Re: Merc 4.3 timing Q

If the Dist wires were mismatched, I would think the engine would not run smoothly. that's the thing, just wanted to check the timing, the engine is not running badly, just not optimal. But something is not right. Tdc is not correct, so I need to find where the error is... I'm leaning toward mis identification of the ig mod

Ayuh,... Like BD said, if the distributor is clocked off a hole or two, yer on a wrong cylinder,...

#1 can be any of the 8 towers on the cap,...

Clamp to #1 wire at the plug end,...

 

[Jacalore]

Re: Merc 4.3 timing Q

Unlikely that both Dist and Plugs are miswired together, but anything's possible! I'll check it out!

 

[Bondo]

Re: Merc 4.3 timing Q

Unlikely that both Dist and Plugs are miswired together, but anything's possible! I'll check it out!

Ayuh,.... You don't seem to understand that #1 can be Any of the towers on the cap,....

That doesn't make anything mis-wired, just clocked off by a tower or 3,...

 

[Jacalore]

Re: Merc 4.3 timing Q

Ayuh,.... You don't seem to understand that #1 can be Any of the towers on the cap,....

That doesn't make anything mis-wired, just clocked off by a tower or 3,...

Gotcha, will check that first.