Weird Timing Issues

[brodie123]

Hi Everyone;

I have a 165HP Mercruiser I/O Inline 6. Timing calls for 6 degrees advance. I'm using 94 octane fuel minimum. The engine was rebuilt recently.

Recently, I installed a MSD 6A for easier cold starts and hopefully a little better gas economy. It for sure helps her cold start easier.

I quickly found that my dial timing light will not work - I had the distributor apart so timing needed to be done. MSD told me to use a standard timing light and that would work fine.

Here's the problem. If I time by ear - under load, let her rattle and back it off quite a bit - I'm getting around 20 degrees advance but runs great - no pings. If I set it back to 10 degrees the motor at idle shakes and starts sounding like she's going to stall. I also lose a lot of upper end hp.

Does anyone here have similair experience with MSD? It's been a while since I've needed to set the timing. Is it possible the timing mark is wrong? Is there a way to confirm the timing mark? Is the MSD mis-guiding the timing light? I really much prefer to be able to confirm my timing vs just by ear.

Please help and thanks!

 

[brodie123]

Re: Weird Timing Issues

here's a quick update. I took out the plugs and whent into cylinder 1 with a camera - the timing mark at 0, piston is right at tdc.

Any suggestions here?

 

[dubs283]

Re: Weird Timing Issues

what is a dial timing light and why can't you use it??

perhaps there is an issue with the light you are using

i use an advance timing light on all ignition systems and never have an issue with it

 

[bruceb58]

Re: Weird Timing Issues

What is your total advance at 3500 RPM?

 

[Pete104]

Re: Weird Timing Issues

What is MSD?

 

[NHGuy]

Re: Weird Timing Issues

MSD is an aftermarket performance company.
What year & model engine is this. And what ignition was in there originally.
If you go from that original info and then follow the MSD instructions maybe you missed something. The Thunderbolt V ignitions require some kind of jumpered connection in the distributor during timing setup to get the advance system out of the way, it's called setting base timing. If that is still needed due to some remaining Thunderbolt V component in the system or distributor it could be your issue.

 

[stonyloam]

Re: Weird Timing Issues

Doesn't the MSD give you multiple sparks? Could that be screwing up the timing light?

 

[brodie123]

Re: Weird Timing Issues

The engine is approx 1981. MSD is a company that makes aftemarket ignition systems. The original ignition was points - I bought the boat with electronic ignition. A dial timing light allows you to "dial" the precise timing but is not compatible with MSD due to multi-spark which is why I bought a straight timing light and use the engine markings. According to MSD support, the system is setup properly.


I guess the quetion is, do I judge by the timing light or is it "safe" to tune the timing by ear??

 

[bruceb58]

Re: Weird Timing Issues

I guess the quetion is, do I judge by the timing light or is it "safe" to tune the timing by ear??

Definitely not.

What is your total timing advance assuming you start at 6 degrees? You need to know this to see if you distributor centrifugal advance is working properly. This could be your whole problem.

 

[brodie123]

Re: Weird Timing Issues

I'll rev her up and post it here. Thx!