Erratic Timing Light Reading on '96 Force 120

[Murph007]

Motor died 20 miles out on Lake Superior when I brought it back to idle to anchor. Was not able to restart the motor except at full throttle but would die when trying to shift into gear. Got back to the house (Towboat US) and did a bunch of maintenance ( re-build the carbs, check the reeds, re-build the fuel pump, new filter, clean the spark plugs, etc) I finally got to the timing stage and I'm stumped to why the timing light will show the timing marks for a second or two then the marks will disappear. Light still flashing but no timing marks showing. Is this a symptom of something to do with the motor or possibly a bad timing light?

 

[Jiggz]

Could be a bad timing light. Remember, the best timing light for this motor is a simple induction type that connects to battery power and the sensor to the #1 spark plug. Start checking the timing tower and its connection to the trigger plate making sure it's all tight. And then inspect all the wirings going through especially under the flywheel that none is corroded or rubbing off any metal parts. Lastly, check the flywheel to make sure it is not loose.

 

[Murph007]

Could be a bad timing light. Remember, the best timing light for this motor is a simple induction type that connects to battery power and the sensor to the #1 spark plug. Start checking the timing tower and its connection to the trigger plate making sure it's all tight. And then inspect all the wirings going through especially under the flywheel that none is corroded or rubbing off any metal parts. Lastly, check the flywheel to make sure it is not loose.

And the winner is: Jiggz!
I just got back from buying another (more simplistic) timing light and Bingo!! - have my timing set and ready to take out for a test run.

Thanks for the reply!

 

[Redbarron%%]

Try the other leads, remembering that they flash at different places around the flywheel. You may have an intermittent timing light or trigger coil or wire. They are small wires and cab break under the insulation.

 

[Murph007]

Try the other leads, remembering that they flash at different places around the flywheel. You may have an intermittent timing light or trigger coil or wire. They are small wires and cab break under the insulation.

Thanks for the reply. It was the timing light that was the problem. Now I'm trying to figure out how to adjust the idle. Not the idle mixture screw but the idle stop bolt at the bottom of the timing tower. Wondering if I need to disconnect all throttle linkage before making the adjustment.

 

[Jiggz]

Thanks for the reply. It was the timing light that was the problem. Now I'm trying to figure out how to adjust the idle. Not the idle mixture screw but the idle stop bolt at the bottom of the timing tower. Wondering if I need to disconnect all throttle linkage before making the adjustment.

If you did not mess with the original timing, it should stay the same. And that means you did not made any adjustment with the timing tower and its connections to the trigger plate. Just to be sure, idle speed around 1000 RPM on muffs and neutral, the timing should be around 8~10 degrees BTDC. Or do the static WOT Timing first which is 32 BTDC.

 

[jerryjerry05]

The 96 120 used the Mercury ignition.
Find the steps for setting the Mercury ignition.

 

[Murph007]

If you did not mess with the original timing, it should stay the same. And that means you did not made any adjustment with the timing tower and its connections to the trigger plate. Just to be sure, idle speed around 1000 RPM on muffs and neutral, the timing should be around 8~10 degrees BTDC. Or do the static WOT Timing first which is 32 BTDC.

I did the 32 BTDC WOT Static. Will get her in the water tomorrow and fine tune the air/fuel mix. What my manual is missing is the idle set screw procedure (located at the bottom of the timing tower arm). I'm assuming that if I need to adjust, I will need to disconnect all throttle linkage to insure that the throttle cam is not being engaged when in neutral idle.

 

[Jiggz]

I did the 32 BTDC WOT Static. Will get her in the water tomorrow and fine tune the air/fuel mix. What my manual is missing is the idle set screw procedure (located at the bottom of the timing tower arm). I'm assuming that if I need to adjust, I will need to disconnect all throttle linkage to insure that the throttle cam is not being engaged when in neutral idle.

No need to disconnect throttle linkage when adjusting the idle screw located at the bottom of the timing tower. All that is required is that you have a 7/16" open wrench to loosen the nut locking the idle screw. And then turn the idle screw in or out depending if you want to increase or decrease idle rpm while holding on the nut with the open wrench. This while you are watching your tach/odom meter. In water neutral, usually you can start with 1000 rpm idle (mine is around 1200 rpm). And then check also the rpm in gear idle and should be around 700~800 rpm. These rpm numbers are not written in stones but more from personal experience. For each boat and motor has their own characteristics that could affect idle rpm in gear, i.e. size of props, size and type of boat, loading, etc.

As for the throttle cam engaging, the only time the throttle cam is not engaged is when you have zero throttle meaning you cannot even start the motor since the throttles are fully closed. You do this only when doing a link and synch and setting the zero timing on #1 spark plug at TDC. Thereafter, as soon as you adjust the idle screw the cam will obviously engage to slightly open the throttles. Hope this helps.

 

[Murph007]

No need to disconnect throttle linkage when adjusting the idle screw located at the bottom of the timing tower. All that is required is that you have a 7/16" open wrench to loosen the nut locking the idle screw. And then turn the idle screw in or out depending if you want to increase or decrease idle rpm while holding on the nut with the open wrench. This while you are watching your tach/odom meter. In water neutral, usually you can start with 1000 rpm idle (mine is around 1200 rpm). And then check also the rpm in gear idle and should be around 700~800 rpm. These rpm numbers are not written in stones but more from personal experience. For each boat and motor has their own characteristics that could affect idle rpm in gear, i.e. size of props, size and type of boat, loading, etc.

As for the throttle cam engaging, the only time the throttle cam is not engaged is when you have zero throttle meaning you cannot even start the motor since the throttles are fully closed. You do this only when doing a link and synch and setting the zero timing on #1 spark plug at TDC. Thereafter, as soon as you adjust the idle screw the cam will obviously engage to slightly open the throttles. Hope this helps.

Thank you! That information seems to be confusing quite a few DIY'rs. Finally found a video that confirms what you said.

 

[jerryjerry05]

Hey mod!! Maybe put a link to this in the stickies ????
THANKS!!

 

[Murph007]

No need to disconnect throttle linkage when adjusting the idle screw located at the bottom of the timing tower. All that is required is that you have a 7/16" open wrench to loosen the nut locking the idle screw. And then turn the idle screw in or out depending if you want to increase or decrease idle rpm while holding on the nut with the open wrench. This while you are watching your tach/odom meter. In water neutral, usually you can start with 1000 rpm idle (mine is around 1200 rpm). And then check also the rpm in gear idle and should be around 700~800 rpm. These rpm numbers are not written in stones but more from personal experience. For each boat and motor has their own characteristics that could affect idle rpm in gear, i.e. size of props, size and type of boat, loading, etc.

As for the throttle cam engaging, the only time the throttle cam is not engaged is when you have zero throttle meaning you cannot even start the motor since the throttles are fully closed. You do this only when doing a link and synch and setting the zero timing on #1 spark plug at TDC. Thereafter, as soon as you adjust the idle screw the cam will obviously engage to slightly open the throttles. Hope this helps.

Update: Got the Bayliner in the water today and turns over strong but no start...... Back to the drawing board!!

 

[Jiggz]

Update: Got the Bayliner in the water today and turns over strong but no start...... Back to the drawing board!!

Oh common! Before you go to the water you need to make sure the motor is running by doing it on the driveway with muffs. Did you try putting the throttle in fast idle? That is pulling the throttle control handle towards you or pushing a center button and pushing it forward. This will give the carbs' throttle some opening to get the motor started.
Now back on the driveway, make sure the throttle cam is engaged against the eccentric screw and that the carbs' throttles are slightly open. Place the throttle control in fast idle position. With a flash light check the carb's throttle to see if its open slightly. DON'T CONFUSE THE CHOKE BUTTERFLIES ON THE FRONT FOR THROTTLES! The throttle's butterflies are behind almost at the "throat" of the carbs. Worse comes to worse, you can hold up the carbs' tie bar (one that connects both carbs throttles) manually while cranking it over. Just to make sure it starts. And if this does not make it start, have a small spray bottle in hand with fuel/oil mix and spray it directly into each carb while cranking. If this still does not make it start or at least cough, then you have spark problem. If it starts with fuel/oil mix spray, you have fuel related or carbs problem. Good luck. Don't forget to rig in the cooling water on muffs. Just make sure you throttle the hose a bit, too much water pressure will dislodge the muffs.

 

[Murph007]

Oh common! Before you go to the water you need to make sure the motor is running by doing it on the driveway with muffs. Did you try putting the throttle in fast idle? That is pulling the throttle control handle towards you or pushing a center button and pushing it forward. This will give the carbs' throttle some opening to get the motor started.
Now back on the driveway, make sure the throttle cam is engaged against the eccentric screw and that the carbs' throttles are slightly open. Place the throttle control in fast idle position. With a flash light check the carb's throttle to see if its open slightly. DON'T CONFUSE THE CHOKE BUTTERFLIES ON THE FRONT FOR THROTTLES! The throttle's butterflies are behind almost at the "throat" of the carbs. Worse comes to worse, you can hold up the carbs' tie bar (one that connects both carbs throttles) manually while cranking it over. Just to make sure it starts. And if this does not make it start, have a small spray bottle in hand with fuel/oil mix and spray it directly into each carb while cranking. If this still does not make it start or at least cough, then you have spark problem. If it starts with fuel/oil mix spray, you have fuel related or carbs problem. Good luck. Don't forget to rig in the cooling water on muffs. Just make sure you throttle the hose a bit, too much water pressure will dislodge the muffs.

Thanks for the advice. It appears I have a spark issue. Finally got around to checking the spark. I have a spark on 1 and 4 plug but not on 2 and 3. Will have to do diagnostics when I have time.

 

[Jiggz]

Hopefully, this is only a case of bad ignition coils. Since 1 & 2 cylinders are fed from the same CD module and 3 & 4 does the same on the 2nd CD module. However, there's also a possibility of both CD mods being faulty. Next step is to switch the ignition coil one at a time, i.e. move #2 to #1 and see if the spark problem follows. If it does then the ignition coil is bad. If it doesn't follow then could be the CD module. Do the same with #3 and #4. Remember, moving coils is not just a matter of switching the spark plug wires but physically moving the coils and its wiring entirely. Goodluck.

 

[Murph007]

Ah, will do and will advise. Thanks again!!

 

[Nordin]

If you are getting confused when switching coils and CDI packs around, have in mind that there is a blocking diod in each CDI pack that have the purpose to block the CDI to interfere with the other one.
This diod can be bad and you can not replace it.
It is in the CDI pack, only way to fix it is to change CDI pack.

 

[Murph007]

I'm done checking everything as per manual ( DVA tester, multi meter, crank switch, etc.) and everything points to the stator - AGAIN!! I just replaced it 2 years ago. Is there something that likes to destroy stators?? Bumpy seas?

 

[Jiggz]

The stator is basically nothing but coils of wire, albeit in these motors there are two separate windings in it, the alternator side which has large windings for charging the battery, usually wire color is yellow. And then the other winding is for the ignition or in your case feeds the switchbox (Thunderbolt ignition system) or the CD Modules (Prestolite System). For 96-120HP the ignition should be Thunderbolt system. On the last stator you replaced, was there any indication of burnt wires or broken wires?

 

[Murph007]

The stator is basically nothing but coils of wire, albeit in these motors there are two separate windings in it, the alternator side which has large windings for charging the battery, usually wire color is yellow. And then the other winding is for the ignition or in your case feeds the switchbox (Thunderbolt ignition system) or the CD Modules (Prestolite System). For 96-120HP the ignition should be Thunderbolt system. On the last stator you replaced, was there any indication of burnt wires or broken wires?

Look like the wires were cooked.