90 hp 1999 Force (Mercury Marine) Flywheel problem

craazy

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Jan 18, 2014
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27
I have a bit of an issue and would appreciate a few suggestions. I posted a little while back about a magnet breaking on my flywheel. The original flywheel on my motor. The correct part number for it is 9008A54. The only place I could find that online was at boats.net. Ordered it and they sent a flywheel with a different part #. (859236T14) ... Before I go any further... I found a used flywheel locally that came off a 75 hp 1998 Force. Tried it on my motor and we just couldn't get the numbers on the flywheel to show up on the light on the timing gun. Ran it for a few seconds while playing around with the timing and couldn't get it to run right. I was told by a respectable mechanic in our area that if the timing marks on the trigger magnets are not the same, it will tell the trigger to fire at all the wrong times and cause the motor to not run right. Back to the new flywheel.. the first thing I looked at when it was shipped to me were the timing marks on the trigger magnets. They are set exactly the same as the one I found locally. About 180 degrees out compared to my original flywheel.

Talked to boats.net and a couple techs at Mercury. All say that flywheel 859236T14 should cross over to my motor. I'm a bit confused being told by a mechanic that if the timing marks are different, it won't work. Then I'm being told that this is in fact the correct flywheel that will work on my motor. What am I missing? Are the timing marks the problem or do I have the correct flywheel and possibly something else electrical is fould up? I will add two pictures trying to demonstrate the location of the timing marks. Thanks for any input!
 

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craazy

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Sorry the pictures came out smaller than expected. I don't have time to re-do right now but will try later. Thanks again.
 

craazy

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Hopefully this will work. This demonstrates where the timing marks on the trigger magnets are located on the original flywheel and the new flywheel. This makes the only difference between the two flywheels that I can think of. Yet I am told the new flywheel will work on my motor. I just don't see how. Any information will most defintitely be appreciated.
 

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Faztbullet

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Mar 2, 2008
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15,589
Check your year model as it looks like you putting on a CDM module flywheel on a switchbox style ignition...
 

pnwboat

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Oct 8, 2007
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Like Jerry suggested, you could use the magnets from the replacement flywheel.

If the zero degree Top Dead Center mark on the outer circumference of the flywheel is not in the same position in reference to the crankshaft keyway slot on the center hole of the flywheel, then I don't think the replacement flywheel will work.

The only other thing that I can think of is to play with the trigger wires that attached to the CDM modules (coil packs). They should be color coded so that you can tell how they were originally set up. If you can figure out which trigger wire fires number one coil at the right time you might be able to compensate for the trigger magnets not being in the same position on the replacement flywheel. All you need is 3 marks on the flywheel 120 degrees apart from each other numbered 1 thru 3 and a timing light. Count the teeth on the flywheel and divide it by 3. That'll tell you how many teeth between each mark.
 

Frank Acampora

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Jan 19, 2007
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12,004
Did you remove the trigger assembly? Mercury used the same trigger for various engines. If not an aftermarket trigger it will say how it is oriented on the engine.
 

craazy

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Jan 18, 2014
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Thanks for all suggestions so far. We had to replace the trigger since the arm on the other one broke when the magnet came loose on my original flywheel. We were careful and placed the stator back on exactly the way it's supposed to be placed. We haven't had the time yet to try this new flywheel. But after comparing my original and the used one I found locally, I have found a couple very small differences between the two. My original and the brand new one are identical in every way besides the timing marks on the trigger magnets. Maybe I'm worrying about nothing with the trigger magnets and my problem with the used flywheel is that it's just a little different perhaps. Hopefully we'll have a little time tomorrow evening to try the new one out and see if we can at least get the numbers on the outer surface of the flywheel to show up on the timing light. The zero degree is perfectly lined up with the keyway slot on all three flywheels.

I will keep you guys updated and maybe we or at least maybe I can learn a few new things about this whole deal. Thanks again.
 

craazy

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Jan 18, 2014
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Got to play around with it today and we finally have her running. We put the new flywheel on then put the timing gun on it and the numbers were showing up on the timing light. (Could not get that to happen with the used flywheel) Gave me a little hope. Got it set on the recommended 28 degrees on the high end. Hooked it up to the hose and muffs and started it up... it sounded awful.

Checked the fire on all cylinders and all were firing. We knew it had to be something with the timing/firing marks on the trigger magnets on the flywheel. They are 180 degrees out from my original.

Thought about what to try for a few minutes. Finally, we just simply switched the number 1 plug wire to the number 3 plug, and the number 3 to number 1. Cranked her up and she sounded perfect.
At least we now know for sure that it was the timing marks on the trigger magnets being 180 degrees out. It was telling my number 1 to fire when my number 3 was supposed to be firing, etc.

Anyways, I ran it up to the lake and it did not miss a beat. The only thing I noticed that was fishy was my RPM gauge was reading as high as 6800 RPMs when I ran it wide open. This motor normally tops out at 5600 RPMs as long as I have had it. My speed hasn't increased nor did the motor feel like it ran any different than it's supposed to. Hopefully just a faulty reading as I have messed around with nearly every wire in the regulator area.

Many thanks to each and everyone of you who have given me suggestions and insight. This site is great. Hopefully my post and all it's replies will come in handy for someone in the future if they happen to encounter the same issue.
 

pnwboat

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Oct 8, 2007
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Sounds like you've got it the timing issue fixed. Now on to the tach problem! If your tach has a selector switch on the back of it, make sure it's set for the correct number of poles on the stator. Yours should be set for 12 poles to read correctly.

Forgot to mention that the Rectifier/Regulator Assy. is where the tach picks up the signal, gray wire I believe. Double check that connection and make sure the Regulator assy. has a good ground connection. Make sure the charging voltage is around 13.5 - 14.5 volts with the engine running at a minimum of about 2000-3000 RPMs. If it's not charging properly, then the Regulator assy. may be bad and causing the RPM's to read incorrectly.
 
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