Flywheel Magnets (six of them)

dlcx1

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Aug 17, 2005
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I looked at all of the posts I could find about flywheel magnets, but have not seen anything about ALL of the magnets coming loose anywhere. I have a 1998 V6 175 Sportjet that I was hearing an odd noise from. Turns out the flywheel is rusty on the underside and the magnets were loose. I have successfully re installed/glued 3 loose magnets on my previous 120 Sportjet, so I know what I need to do. The question is with all of the magnets loose, what do I need to worry about as far as correct positioning? All of the magnets are still in one piece, with only a little bit of the corner on one missing. The boat has been running fine. The underside of the flywheel just has too much rust on it to confirm the locations of any of the magnets except for maybe one of them. I am thinking that as long as I have the polarity correct and the spacing equal all the way around, I should be OK. Can anyone verify this? I can tell by looking at the magnets which way is up from the paint remaining on them.
 

sschefer

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Re: Flywheel Magnets (six of them)

I looked at all of the posts I could find about flywheel magnets, but have not seen anything about ALL of the magnets coming loose anywhere. I have a 1998 V6 175 Sportjet that I was hearing an odd noise from. Turns out the flywheel is rusty on the underside and the magnets were loose. I have successfully re installed/glued 3 loose magnets on my previous 120 Sportjet, so I know what I need to do. The question is with all of the magnets loose, what do I need to worry about as far as correct positioning? All of the magnets are still in one piece, with only a little bit of the corner on one missing. The boat has been running fine. The underside of the flywheel just has too much rust on it to confirm the locations of any of the magnets except for maybe one of them. I am thinking that as long as I have the polarity correct and the spacing equal all the way around, I should be OK. Can anyone verify this? I can tell by looking at the magnets which way is up from the paint remaining on them.

Magnet positoning is pretty critical. If you're off by too much you will have weak spark. If it's a 16 amp system it's not a big deal because you can rotate the stator to accomdate the problem. With a 40 amp system the stator can only be mounted in one position.. At least that's the way it is with the three different styles that I have.

You can buy a used flywheel on ebay pretty cheap. It might be worth it considering the rust problem and all.
 

Dave1027

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Re: Flywheel Magnets (six of them)

I'd for sure get a new flywheel. Not getting the magnets exactly correct would throw off the timing. The motor would never run right.
 

dlcx1

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Messages
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Re: Flywheel Magnets (six of them)

The rust is mostly surface and fairly light. (mostly red dust) It will clean up easily. With the motor starting easily and running well with loose magnets, I question really how close to an exact position do they really need to be? I believe I can position one of them from the marks on it. The others would be evenly spaced around the flywheel. I stopped working on it and will look more closely to locate at least one tomorrow.
 

j_martin

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Re: Flywheel Magnets (six of them)

Magnet positoning is pretty critical. If you're off by too much you will have weak spark. If it's a 16 amp system it's not a big deal because you can rotate the stator to accomdate the problem. With a 40 amp system the stator can only be mounted in one position.. At least that's the way it is with the three different styles that I have.

You can buy a used flywheel on ebay pretty cheap. It might be worth it considering the rust problem and all.

I'm going to have to disagree with you. If they're reasonably evenly spaced, and the polarity is right, the sinusoidal output of the stator should be fine. Stator output is not time critical. Only the trigger output is time critical, and that is generated from a different set of magnets in the hub.

hope it helps
John
 

dlcx1

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Re: Flywheel Magnets (six of them)

That probably explains why it was/is still running good, even with the magnets all bunched up one side of the flywheel. I think I will still locate least one if I can make out the marks and go from there.
 

Dave1027

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Re: Flywheel Magnets (six of them)

I'm going to have to disagree with you. If they're reasonably evenly spaced, and the polarity is right, the sinusoidal output of the stator should be fine. Stator output is not time critical. Only the trigger output is time critical, and that is generated from a different set of magnets in the hub.

hope it helps
John
John I was thinking about trigger timing when I posted. I thought the same magnets were used for both. Where are the trigger magnets located?
 

j_martin

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Re: Flywheel Magnets (six of them)

John I was thinking about trigger timing when I posted. I thought the same magnets were used for both. Where are the trigger magnets located?

Trigger magnets are in the hub. there's only 2 poles. There's 3 coils in the trigger, each puts out a sinusoidal waveform, one cycle per revolution, 120 degrees out of phase with the other 2.
 

Dave1027

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Re: Flywheel Magnets (six of them)

Trigger magnets are in the hub. there's only 2 poles. There's 3 coils in the trigger, each puts out a sinusoidal waveform, one cycle per revolution, 120 degrees out of phase with the other 2.

Hub? Do you mean the crank?
 

j_martin

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Re: Flywheel Magnets (six of them)

Hub? Do you mean the crank?

The splined hub part of the flywheel. It separates from the outer flywheel on some with a flexplate. On most of the 40 amp flywheels, it's solidly built in. There is a smooth cover over the magnets.

The trigger is under the stator. It isn't any where near the flywheel magnets that run the stator.

hope it helps
John
 

sschefer

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Re: Flywheel Magnets (six of them)

The splined hub part of the flywheel. It separates from the outer flywheel on some with a flexplate. On most of the 40 amp flywheels, it's solidly built in. There is a smooth cover over the magnets.

The trigger is under the stator. It isn't any where near the flywheel magnets that run the stator.

hope it helps
John

The center hub of the flywheel houses two sets of magnets in layers. The lower set is oriented with opposite polarity of the upper. This why with 3 trigger coils you get six trigger pulses in a single rotation.

The magnets attached to the outer portion of the flywheel either by glue or screws have a dual function in that they serve both the stator charging coils for the battery and the stator ignition coils, (not to be confused with the coils connected directly to the spark plug wires).

There are two sets of ignition coils. One set is for low speed operation and the other for high speed operation and some point around 2000 RPM both are functional but only as the transition from low to high is occuring.

When a magnet passes over the ignition coil it creates a voltage of a certain amount that charges the capacitor in the switchbox. The desire is that the switch box capacitor be at full charge when the trigger voltage is produced that causes the switch in the switch box to close and allows the voltage from the capacitor to flow to the spark plug coil.

If the magnets are improperly adjusted there is the possibility that the trigger will fire before the capacitor is fully charged and the result would be a reduced spark or possibly no spark at all. This would be most common in the 9 amp stators but can also occur in the 16's and 40's.

40 amp flywheels have removable center hubs that can be adjusted to compensate for magnet placement problems. The 16 amp flywheels may or may not have them so the 16 and 9 amp stators are adjusted by moving them one screw hole in either direction. The 40 amp stators are fixed position when installed correctly and cannot be adjusted so you would move the center hub instead.

Newer 40 amp flywheels are sometimes marked with a white dot to indicate where the stator should be in relation to the flywheel.

Late additon edit: Forgot to mention this but if you have a timing light with an advance feature, you can set your max timing (WOT) then adjust the advance feature to that number and try to hit "0". If your stator or your magnets are off, it won't hold steady because you'll be misfiring and possibly double firing the spark plug coils. Just to add another wild and crazy merc ignition problem to the list..:)
 

dlcx1

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Aug 17, 2005
Messages
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Re: Flywheel Magnets (six of them)

Cleaned everything up and glued 'em all back in. Starts and runs fine. Everything almost back to normal now. (I've still got other problems with it) Thanks for everyone's input.
 
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