TB 4 ignition timing question

[chris008]

I just replaced my ignition sensor, coil, dist cap/rotor, plug and wires on a 1987 Mercruiser 5.7 with a TB 4 ignition. The boat is now running rough and wont idle. It ran fine before I did the work with the exception of an intermitted "worn't run" problem that I attributed to an overheated ignition sensor. Do I need to adjust the timing since I replace the ignition sensor? If so, what is the correct timing?

 

[Don S]

Re: TB 4 ignition timing question

It sure wouldn't hurt to check it and make sure nothing moved. Also make sure your plug wires are in the proper firing order. That could be your rough running.
Also be sure to check the advance timing.
You can find a link to the OEM service manual up in the Adults Only sticky at the top of this forum. Then you will have all the information.

 

[chris008]

Re: TB 4 ignition timing question

thanks for the reply, but I am not finding the Adults Only sticky. can you point me in the right direction?

 

[Don S]

Re: TB 4 ignition timing question

It's the first post in the list of posts for this forum.

 

[chris008]

Re: TB 4 ignition timing question

thanks. i found the manual. It states the timing should be set to 8 deg BTDC at idle. I found other publications that stated it should be 10 dg BTDC. Do you know which is correct. Again, 1987, TB4 ignition, carburated.

 

[JustJason]

Re: TB 4 ignition timing question

8 will do ya just fine.

 

[Don S]

Re: TB 4 ignition timing question

You have an 87 engine, you need to look at manual #9, it says 8? BTDC, why would you be looking at other publications that DON'T have your model in it.?????

 

[jtybt]

Re: TB 4 ignition timing question

Also, Your ECM will have a number on it stating the model. It will say something like V8-24 or V8-24S or even V8-HP or V8-22. That tells you the advance designed into the ECM.