Timing help please

[sawblade723]

OK, I have removed the advance module from my 1986 merc 150 XR2 because of corroded wiring. My manual says timing should be 11ATDC throttle pickup - 26BTDC max - 22BTDC@cranking speed. With the module removed do I stay with these numbers or do I need to alter the timing to make up for the electronic advance being removed?

 

[sschefer]

Re: Timing help please

OK, I have removed the advance module from my 1986 merc 150 XR2 because of corroded wiring. My manual says timing should be 11ATDC throttle pickup - 26BTDC max - 22BTDC@cranking speed. With the module removed do I stay with these numbers or do I need to alter the timing to make up for the electronic advance being removed?

23-25 for WOT at cranking speed.
Start with 11 on initial and then adjust it so that the engine idles around 850 on the hose and if you quickly rap the throttle the idle does not drop off and stall that engine.

The intital timing is just a starting point that the engine should run at. WOT at 23-25 is safe, you could push it up to 26 but keep a sharp ear out for detonation. If it doesn't happen, enjoy the ride!

 

[sawblade723]

Re: Timing help please

Thanks, thats what I needed to know, I will stop it at 25 BTDC to be on the safe side. My hearing is not that good and I may not hear the detonation.

 

[j_martin]

Re: Timing help please

Thanks, thats what I needed to know, I will stop it at 25 BTDC to be on the safe side. My hearing is not that good and I may not hear the detonation.

If yer running 87 octane pump gas, back it off a bit. (23) That would be fine with the classic car gas, 91-92 octane no alcohol.

All the module did was advance the idle timing a bit if it got too slow.

hope it helps
John

 

[sawblade723]

Re: Timing help please

Yeah, I usually run the pump gas, I will back it down to 23. I dont want to sling it apart just want it to run good.

 

[j_martin]

Re: Timing help please

Yeah, I usually run the pump gas, I will back it down to 23. I dont want to sling it apart just want it to run good.

I put in a toggle switch and resistor to kick the timing up 2-3 degrees at will. At WOT it really didn't make much difference. Engine note changed very slightly. Speed or RPMS didn't change.

It was a bone stock XR4 (except the advance module is removed) at 6100 RPM. That pretty well max's out the vertical front and porting on that motor.