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I have a 1991 Yamaha 90TLRP ignition timing is jumping all…

I have a 1991...

I have a 1991 Yamaha 90TLRP ignition timing is jumping all over the place.

Mechanic's Assistant: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.

Compression is 120psi in all three cylinders. I have a manual that want's 8 degrees ATDC at idle and 20 degrees BTDC WOT

Mechanic's Assistant: Is there anything else the Marine Mechanic should be aware of?

The engine sputters and will stall but it coincides with erratic timing movement if you have a timing light on it. I was suspecting a pulser coil or CDI?

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Customer reply replied 8 months ago
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Answered in 1 hour by:
10/21/2017
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 17,428
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
Verified

Hello my name is***** to electromagnetic interference that outboards experience, not all timing lights will work on all engines. The interference ends up effecting the light itself. Have you tried a different timing light yet in order to rule out that possibility?

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Customer reply replied 8 months ago
I actually do have another timing light and I can try it ( not today) I do politely but strongly doubt this because the engine is stumbling in time with the timing blips and I have used this light on my suzuki dt65 and it is a MAC light with a two stroke switch for tach

I keep 3 different timing lights in my tool box for exactly this reason. I have 1 Snap on, 1 Equus, 1 Stephens brand. 1 of them is self powered with D batteries and the other 2 clip the battery like a standard light. I can tell you that not all lights work on all engines. There is no rhyme or reason for this other than manufacturing differences. Sometimes my cheapest light works when my most expensive one doesn't and vice versa. What you want to keep in mind is most timing lights are designed to work on automotive engines, were there is very little magnetic interference. Your outboard huge magnet on the top of it that spins with engine RPM. That washes the entire engine with electromagnetic interference. So try a different light first and see what happens. If it still does the same thing then the most likely issue is a bad CDI box or a loose flywheel on the crankshaft. There is a woodruff key that locks the flywheel to the crankshaft, if that key ever shears (and they do) The flywheel will become loose on the crankshaft and throw it out of time. If your 2nd light does confirm the timing is jumping you would pull the flywheel and inspect the key as well as check the flywheel out for broken magnets. If those do end up looking good as well, then you would replace the CDI box. Does that all make sense. I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

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Thanks in advance, and good luck
Jason

Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 17,428
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
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Customer reply replied 8 months ago
Jason thanks. I had previously pulled the flywheel to check the woodruff key because that happened to me on my suzuki engine. I will use the other light tomorrow.

Good morning. You are very welcome. Let me know how you make out.

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