1999 mercruiser base timing, Thunderbolt V ignition

[onebighead]

I am working on 1999 305 chevy mercruiser with tbi system. Serial is L619326, with a thunderbolt V system. Now needing to set base timing, and I can't find a stand alone purple white wire near the distributer. My system has 2 wires leading into the dist., one is a purple white in a connection, but when I disconnect this wire and ground it, my engine will not start. Where am I going wrong here? Is there another purple white wire that I am missing? and is it a free-standing wire? would like response, thanks

 

[Don S]

Re: 1999 mercruiser base timing, Thunderbolt V ignition

Stbd side of the engine, next to, or just slightly in front of the carb is where you will find the wire.

 

[onebighead]

Re: 1999 mercruiser base timing, Thunderbolt V ignition

Thanks Don S for the reply. This boat does not have that purple white wire as described. It does have a gray wire that is quite obvious with a rubber cap in the area. I have examined the cable of wires around the tbi, and I see no purple white wire. As mentioned above, there is a purple white wire going to distributer, but when grounded, the engine will not start. Is it possible that this gray wire is "the one" to ground for base timing?

 

[achris]

Re: 1999 mercruiser base timing, Thunderbolt V ignition

Gray wire is tacho signal....

 

[achris]

Re: 1999 mercruiser base timing, Thunderbolt V ignition

Ummm. My system says that engine doesn't have Thunderbolt V, it has one of the MEFI systems... And yes, the purple/white wire DOES have something connected to it.... And if you only have 2 wires going to the dissy, it's MEFI-3, with a Mercury distributor ....

Give me a couple of minutes and I'll find the timing procedure for you...

Chris.....

 

[achris]

Re: 1999 mercruiser base timing, Thunderbolt V ignition

Ohhhhh, you're really not going to like this.....

Got access to a timing tool? (or scan tool)



The 'timing tool' part number is 91-805747A2. It's only $12 from a Merc dealer... I guess that's a bit of comfort....

HTH,

Chris.........
EDIT: With Don's help we found that all you need to do to put it in 'timing mode' is short terminals A and B in the diagnostic connector (DLC). That's a blk/wht and a black wire... The DLC is a 10 pin connector with a cap on it. Half a paper clip will do just nicely.

 

[Don S]

Re: 1999 mercruiser base timing, Thunderbolt V ignition

I just looked up the serial number too, and sure enough, EFI. I didn't look it up before because I ASSUMED it was a carbed engine.

PS: Chris, your picture didn't show up.

 

[achris]

Re: 1999 mercruiser base timing, Thunderbolt V ignition

I am working on 1999 305 chevy mercruiser with tbi system. Serial is L619326, with a thunderbolt V system. Now needing to set base timing, and I can't find a stand alone purple white wire near the distributer. My system has 2 wires leading into the dist., one is a purple white in a connection, but when I disconnect this wire and ground it, my engine will not start. Where am I going wrong here? Is there another purple white wire that I am missing? and is it a free-standing wire? would like response, thanks

I just looked up the serial number too, and sure enough, EFI. I didn't look it up before because I ASSUMED it was a carbed engine.

PS: Chris, your picture didn't show up.

^^^^

We're getting old Don....

Picture ok now?

 

[onebighead]

Re: 1999 mercruiser base timing, Thunderbolt V ignition

Thanks so much achris and Don S. Now I think I can get it done. Sorry for misleading info. stating it was tbV system. I will now procede and keep you posted. thanks

 

[Don S]

Re: 1999 mercruiser base timing, Thunderbolt V ignition

Glad you posted, couldn't remember which thread it was.
There is an old thread that shows how to put your ecm into service mode without the special tool if you want to try it.
http://forums.iboats.com/mercruiser...timing-tool-make-1-00-a-49800.html#post448079

 

[onebighead]

Re: 1999 mercruiser base timing, Thunderbolt V ignition

Don S and achris, thanks again. This is just a follow up. All is well now. I did use your information to make a tool to read any codes in the ecm. . (The led and paperclip in the dlc plug) It worked like a champ. later