Timing at idle speed?

[iwaterdave]

All posts and repair book mention setting the timming at W.O.T. and need a special prop to put on to do this without the boat moving. Can't I just check the timing at idle like any other vehicle?

86' 125 Force Outboard

 

[Jiggz]

Re: Timing at idle speed?

Actually, you cannot. The reason being the timing mechanism is totally different with cars. Force motors timing is purely mechanical in nature and is not variant or do not change directly with the RPM; instead it changes with the throttle position.
You can still set the timing using static method. Using a TDC tool or dial indicator set the #1 cylinder to TDC and then check the setting of the timing park on the flywheel with the timing pointer.
This pointer is mechanically link to the tower shaft directly linked to the throttle position. With the idle screw set at minimum (the line on the cam should line up with the eccentric screw line) and throttle valve close, the timing pointer should be set at zero advance.
Now move the throttle to WOT position (verify throttle valves are in horizontal position) and the pointer should advance to 34 degrees (double check this). Now you are statically timed. Now you can set your idle screw again for the engine to idle at 750 RPM in gear or 1000 RPM in neutral.
Another method of setting timing is called dynamic timing using a timing light. This method is easier but requires a good timing light.

 

[iwaterdave]

Re: Timing at idle speed?

Actually, you cannot. The reason being the timing mechanism is totally different with cars. Force motors timing is purely mechanical in nature and is not variant or do not change directly with the RPM; instead it changes with the throttle position.
You can still set the timing using static method. Using a TDC tool or dial indicator set the #1 cylinder to TDC and then check the setting of the timing park on the flywheel with the timing pointer.
This pointer is mechanically link to the tower shaft directly linked to the throttle position. With the idle screw set at minimum (the line on the cam should line up with the eccentric screw line) and throttle valve close, the timing pointer should be set at zero advance.
Now move the throttle to WOT position (verify throttle valves are in horizontal position) and the pointer should advance to 34 degrees (double check this). Now you are statically timed. Now you can set your idle screw again for the engine to idle at 750 RPM in gear or 1000 RPM in neutral.
Another method of setting timing is called dynamic timing using a timing light. This method is easier but requires a good timing light.

Ok, so if I have to set it at W.O.T. can I just take the prop off since I don't have access to the test prop that is mentioned in the repair manuel? I do have a good timing light but thought it should be set at 30 degrees instead of 34 degrees you mentioned. I'm going to the docks tomorrow morning to try and set the timing so any input would be helpful.

 

[jerryjerry05]

Re: Timing at idle speed?

You set static timing with the motor off.
Check top post in the Force forum.
There is a post covering the static timing.
http://forums.iboats.com/showthread.php?t=449011
No need for special prop.
Make sure the plug leads are grounded.
If not you can blow the packs.

 

[Frank Acampora]

Re: Timing at idle speed?

Drain the fuel bowls of the carbs so the engine will not start. Now, set the control handle in full forward gear. set your timing light pick-up on the top plug wire and clamp the power cables to the battery. Turn the key to "RUN" position. Using a remote starter switch from battery to yellow wire on the solenoid, crank the engine while pointing the light at the flywheel. Set timing to 28degrees before TDC if it is an older Force. When running, the timing will advance to 30 degrees which is the correct setting. Don't know if the same is true for the newer Force with Mercury ignition. You can set it to 30 degrees--if it advances to 32 it will not harm anything Or you can set it to 28 and if it does not advance the two degrees you will lose a couple of RPM--Note--a couple, not a couple of hundred.

Timing at idle can vary around a couple of degrees (or more in some cases) so it can not be used to set the important WOT timing.

 

[iwaterdave]

Re: Timing at idle speed?

Drain the fuel bowls of the carbs so the engine will not start. Now, set the control handle in full forward gear. set your timing light pick-up on the top plug wire and clamp the power cables to the battery. Turn the key to "RUN" position. Using a remote starter switch from battery to yellow wire on the solenoid, crank the engine while pointing the light at the flywheel. Set timing to 28degrees before TDC if it is an older Force. When running, the timing will advance to 30 degrees which is the correct setting. Don't know if the same is true for the newer Force with Mercury ignition. You can set it to 30 degrees--if it advances to 32 it will not harm anything Or you can set it to 28 and if it does not advance the two degrees you will lose a couple of RPM--Note--a couple, not a couple of hundred.

Timing at idle can vary around a couple of degrees (or more in some cases) so it can not be used to set the important WOT timing.

Can't I just disconnect the fuel line so it won't start?

 

[iwaterdave]

Re: Timing at idle speed?

You set static timing with the motor off.
Check top post in the Force forum.
There is a post covering the static timing.
http://forums.iboats.com/showthread.php?t=449011
No need for special prop.
Make sure the plug leads are grounded.
If not you can blow the packs.

Can I just remove the prop to perform the WOT timing? Or is a special prop required? And I'm sure I need to set this timing eather way in a tank rather from the muffs right?

 

[jerryjerry05]

Re: Timing at idle speed?

The motor needs a load on the prop for WOT timing.
Static timing is done not running.
To set WOT timing you need to be under way(dangerous) or in a tank with the special wheel.
Just setting it to static is all you need to do.
I've ran mine like that since I bought them new in 88.
Still fuel in the bowls when you disconect the line.J

 

[iwaterdave]

Re: Timing at idle speed?

The motor needs a load on the prop for WOT timing.
Static timing is done not running.
To set WOT timing you need to be under way(dangerous) or in a tank with the special wheel.
Just setting it to static is all you need to do.
I've ran mine like that since I bought them new in 88.
Still fuel in the bowls when you disconect the line.J

Jerry,
I just did the static timing as you suggested. However after setting my light to 28 and adjusting the screw till the TDC lines up with timing line it runs worse and won't stay started when connecting the garden hose.
Suggestions?

 

[TwoFish]

Re: Timing at idle speed?

The manual I have has the static timing as 34 BTDC and the dynamic timing as 32 BTDC for a 1984-89 125hp.

All the static times are 2 degrees more advanced than the dynamic times in the manual.

I have seen two different versions of how to set static timing. One says to set it 2 degrees more retarded than the dynamic time and the other says to set it more advanced. I am only new to working on outboards and I?m very appreciative of the help I?ve received on this forum. Can anyone clear this up?

My thoughts on it are that the static timing needs to be more advanced than the dynamic.

My reason is that if there is any delay in the time it takes for the timing light to react it will move the timing towards top dead centre the faster the flywheel spins. 34 BTDC on the flywheel comes past the timing mark before 32BTDC. If there is a delay in the timing light this time allows the flywheel to turn more at 5000 rpm than at cranking speed moving the mark you see closer to TDC.

For the static time to be less than the dynamic time (eg static 30BTDC, dynamic 32BTDC) the delay time would need to be less at higher rpm than low rpm . I can?t see how this would happen.


I did some maths to work out how may degrees the flywheel turns at different speeds and how much time it would take for the flywheel to turn 2 degrees at 5000 rpms.

At 300rpm (guess of cranking speed) the flywheel turns 1,800 degrees every second. 300 x 360 = 108,000 degrees per minute. 108,000 divide 60 seconds =1,800 degrees per second.

At 5000rpm (dynamic timing speed) the flywheel turns 30,000 degrees every second. 5000 x 360 = 1,800,000 degrees per minute. 1,800,000 divide 60 seconds =30,000 degrees per second.

The time it takes for the flywheel to rotated 2 degrees at 5000 rpm is 0.000067 of a second.
2 degrees divided by 30,000 degrees = 0.000067 of a second

You only need a delay of 0.000067 of a second to make a 2 degree difference at 5000 rpm.

At 300 rpm the delay only makes a difference of 0.12 of a degree.
1800 degrees (degrees per second at cranking) x 0.000067 (delay time for 2 degrees at 5000rpm) = 0.12 degrees.

To my way of looking at it if you have set your timing statically to 28 BTDC it will be 26 BTDC dynamic. This makes it 6 degrees too retarded. I?m not suggesting you change it as I?m not sure I am right. It wouldn't be the first time I have I've put 2 and 2 together ang come up with 5.

I suppose the only way of testing this is to set the timing statically and then remeasure it at 5000 rpm. I haven?t done this yet. I?d be interested in what other people think

 

[iwaterdave]

Re: Timing at idle speed?

The motor needs a load on the prop for WOT timing.
Static timing is done not running.
To set WOT timing you need to be under way(dangerous) or in a tank with the special wheel.
Just setting it to static is all you need to do.
I've ran mine like that since I bought them new in 88.
Still fuel in the bowls when you disconect the line.J

Called around and no one sells the special wheel to do the WOT timing. So had the wife drive the boat in a straight line and set timing to 30 degrees. (86' 125 Force Outboard) However at idle it runs rough. Any idea's? I have the idle screw all the way in as if I back it out it struggles and dies. What should the RPMs be at idle speed or just barley in gear?

 

[Jiggz]

Re: Timing at idle speed?

You cannot set dynamic timing with idle not properly set. I highly recommend you set it statically first and then fix the idling issue. If you have the idle screw all the way in, it means to say your idle port or idle circuit is not even working. Are you sure the engine is not misfiring? compression tests? As for the timing advance, for 125 HP with prestolite ignition it is set 2 degrees retarded at cranking speed which is 26 degrees. For thunderbolt ignition (CDI and CDM) it is set 2 degrees advance at cranking speed which is 30 degrees. In short, the WOT timing is 28 degrees.

 

[TwoFish]

Re: Timing at idle speed?

Thanks for that Jiggz.

Two different ignition systems accounts for the why I have seen both retard and advance settings for static timing.

 

[Jiggz]

Re: Timing at idle speed?

It makes sense but then checking on a different manual it states for 125 HP the maximum advance is 34 degrees at static and 32 degrees at WOT ??? I'll start with the conservative 28 degrees and test for max rpm every two degrees.

 

[jerryjerry05]

Re: Timing at idle speed?

The IDLE screw is an AIR screw.It should be set at 1 turn out for initial testing.
Do a compression test.

 

[Frank Acampora]

Re: Timing at idle speed?

Twofish: You can do all the math you want, but degrees turned at RPM is not the reason the static and dynamic timing is different. Electricity moves at the speed of light and practically speaking there is absolutely no "delay" in the timing light. Essentially, at the exact moment the sparkplug fires, the timing light strobe will fire also.

The real reason that static and dynamic timing is different is because there are magnets under the flywheel that tend to move the trigger within the "slop" of the linkage more at running speed than at cranking RPM

 

[jerryjerry05]

Re: Timing at idle speed?


The pics are of the wires I fixed up to ground out the plugs for testing.

(I just did the static timing as you suggested. However after setting my light to 28 and adjusting the screw till the TDC lines up with timing line it runs worse and won't stay started when connecting the garden hose.)
The timing light should be set at zero if it's an adjustable.
The 28deg is the first hash mark of the 3 marks together.
The single hash mark is for finding TDC while the motor is off and using a screwdriver or a special tool.That tells you if the key is sheared.

You do a compression test?Just checking??

 

[iwaterdave]

Re: Timing at idle speed?

View attachment 159341View attachment 159342
The pics are of the wires I fixed up to ground out the plugs for testing.

(I just did the static timing as you suggested. However after setting my light to 28 and adjusting the screw till the TDC lines up with timing line it runs worse and won't stay started when connecting the garden hose.)
The timing light should be set at zero if it's an adjustable.
The 28deg is the first hash mark of the 3 marks together.
The single hash mark is for finding TDC while the motor is off and using a screwdriver or a special tool.That tells you if the key is sheared.

You do a compression test?Just checking??

Thanks for the info. I have to say I'm a bit dissappointed in the compression I got.
#1 30lbs
#2 60lbs
#3 70lbs
#4 70lbs

So anyone thinking the same thing I am? Rebuild...

 

[jerryjerry05]

Re: Timing at idle speed?



You pull all the plugs when you did the test?
A screw in tester or a push in?
Screwin is by far better!
It's a wonder it starts at all???

Remove all the plugs.
Key OFF use a jumper box on the solenoid..
Throttle open all the way.
Screw in tester and turn over till the guage stops going up.
Repeat on the rest.
Then post the results.