Strange Timing Issue

[pbxcomm]

Hi all..
I appreciate all of your input past and present... Thank you.

To my issue.. I've never run in to this before (after 40 years). I own a 2000 125HP 2 Stroke (yes, 2+2) hold the comments, hahaha..
It has 150 LBS compression on all cylinders so it been a reliable gem for my 22' pontoon.
Quickly here is my issue. I checked static timing it was off a few degrees. I set it to 23 degrees as stated on the air box. By the way I check timing with an INNOVA Pro Digital Timing Light. When I'm out in the lake WOT (my wife is driving) I check the timing and its more than 8 degrees difference than static (approx. 15 degrees BTDC).
Do I have a bad stator? Thoughts? I have a DVA meter and test harness, but its the holiday weekend and thought perhaps any one here may have experienced this issue?

Thanks

[pbxcomm]

Hi all..
I appreciate all of your input past and present... Thank you.

To my issue.. I've never run in to this before (after 40 years). I own a 2000 125HP 2 Stroke (yes, 2+2) hold the comments, hahaha..
It has 150 LBS compression on all cylinders so it been a reliable gem for my 22' pontoon.
Quickly here is my issue. I checked static timing it was off a few degrees. I set it to 23 degrees as stated on the air box. By the way I check timing with an INNOVA Pro Digital Timing Light. When I'm out in the lake WOT (my wife is driving) I check the timing and its more than 8 degrees difference than static (approx. 15 degrees BTDC).
Do I have a bad stator? Thoughts? I have a DVA meter and test harness, but its the holiday weekend and thought perhaps any one here may have experienced this issue?

Thanks

Hi all..
Here is an update..
I checked the Stator, Trigger and all four CDM's. They all checked ok with a DVA/Harness/Meter.
Static timing is still close to 30 degrees, yet out in the boat/lake at WOT the timing is spot on at 25 degrees. Idle timing is set to 2 degrees.
Any thoughts on how these timings can be so far off?

Thanks..

[Jim Speros]

Years ago it was suggested not to use an advance timing light. Anyway there will be some variation at cranking speed. Are you cranking with plugs in? Varying voltage will effect engine timing and timing light advance.
The important setting is at speed. I used to set timing to prepare for ramp then When I got there I checked and adjusted as needed with boat ramped and still on the trailer. With proper height and trim you can pull a full load at max advance with running voltage near 14 volts.

[pbxcomm]

Hi Jim..
Thank you for your reply..
I do check static timing with all plugs out, fully charged battery (12.8 volts). The number one plug I have grounded to block. You mentioned not to use advance timing light, coincidentally, I found someone with a new Merc timing light, the timing light that the service manual recommends. I'll start there, I'm hopeful this will resolve the issue.
When out in the lake, I check timing at or around 4000 to 4500 RPM, the timing mark is steady from launch (1100 RPM) to 4500. If I revert static timing to 23 (25 is recommended full advance), then lake test reveals a timing at or around 18 to 20 degrees. I'm wondering if a bad rev limiter is at fault? Anyway, I'll connect the new timing light and chime in with results.

Thanks again. I do appreciate your input.

- Marc

[pbxcomm]

Hi all.. Could use some additional input, I'm stuck..
I purchased a Mercury timing light as I thought my pro timing light was giving me incorrect timing readings
The timing light: Mercury 91-99379 (new in box).
Re-check timing at idle, I set to 2 degrees
Static timing (at cranking) is 29 degrees and should be 23 at cranking.
WOT timing out on the lake is steady at 25 degrees.
Looking at the plugs, they look as they always do somewhere between ideal and rich.

Any thoughts why the static timing at cranking would be 6 degrees advanced from where it should be yet WOT is exactly where it should be at 25 degrees?

Thanks much

[pbxcomm]

Hi all..
To summarize.. (I have tendencies to over function)..
In order to achieve 25 degrees WOT timing (out on the lake over 3000 RPM) I need to compensate for the 6 degree difference with the timing screw.
If I set static timing to 23 degrees, it also affects the advance timing by 6 degrees, so I need to advance the timing screw accordingly to achieve 25 degrees.
I would normally be concerned, but I check it each day i go out and WOT timing is 25 degrees steady.

[OnPad]

Do you have a service manual that has timing specs?

I know nothing of your particular engine, but my service manuals for it's bigger brothers specify a cranking number. This could be 16 to 25 degrees depending on the model. The manual also has timing spec at a certain rpm, or throttle setting. This number could only be 1, or up to 6 degrees different than cranking. This variation is caused by different modules, that most people around her throw in the garbage. You say you have cdm coils, this indicates to me your engine is new enough that throwing modules in the garbage is likely not a option.

I'm in the process of retrofitting older electronics on a 2000 mercury 200. The manual states that it has a 6 degree difference, 24°cranking, and 18° at 5800rpm.

[pbxcomm]

Thanks for the reply..
The sticker on the airbox indicates 25 degrees at 300 RPM, or cranking and 23 degrees @ 3000. I've been playing with timing attempting to find a medium.
So, it is 2 degrees difference according to the service manual and airbox, however I'm reading timing now at 6 degrees difference. So, cranking is at 29 degrees while WOT on the lake is 24 - 25 degrees.
something is affecting my timing 6 degrees. There is a REV limiter on this motor (the only module) but I don't believe that this specific module affects timing it only cuts out the ignition temporarily. I could be wrong and have a bad REV Limiter?

[pbxcomm]

I can deal with 2 degrees + or - .. 23 at WOT or 25 at WOT, but I'm dealing with 6 degrees difference between cranking and 3000 RPM.

[OnPad]

Idk if that engine has a bias test that could be done?
I think that wire is used to control timing. On my cdm engine, bias is the test for a defective control module.

[pbxcomm]

Thanks again for your reply..
I see there is a forward bias test and a reverse bias test for the CDM's.
Interestingly enough the REV limiter is listed as a 821889A51 "reverse limiter assembly".
There is no mention in the service manual of the REV limiter affecting timing, but it does connect to BLK/YEL which is the bias circuit.
I'll check this out.. Thanks for the advice. Always helpful to have another perspective..

Regards/Marc

[Jim Speros]

Blk/yellow is kill. Wht/ blk is bias.

I have never been comfortable with the variation of timing between cranking speed and running. I always final check at ramp while still on trailer where I could pull r's with full load.

[pbxcomm]

Jim.. I believe your correct.. I'm sticking with WOT timing on the lake with full load. To add to this is my own ignorance. This motor requires 25 degrees BTDC cranking, 23 Degrees MAX BTDC. I was setting the timing in reverse (23 cranking/25 WOT).

I had attended Mercury school Fond u lac and Oshkosh and became certified back in 1976. I work on Mercs from time to time since then and think I know enough to ignore the obvious. This is a good example.

I want to thank you ALL for taking time out of your busy schedules to help me here. Your input forced me to re-think and focus on the obvious.

Thanks to Screamandfly! They have been here for everyone!!

[Aaronhl]

What do you mean cranking/WOT would you open the throttle all the way while cranking? Or are you really riding the back at 6000