Flywheel magnets

albert1

Cadet
Joined
Jul 16, 2009
Messages
9
Hi,
I have replaced 5 magnets on my 1996 90elpt force flywheel with magnets I salvaged from a similar year date and size Mercury 3 cyl engine, the magnets are the same size and shape but do seem slightly weeker.
I am getting a spark to all 3 plugs but the engine will not start, sounds the same as when you try with the kill switch off.
prior to replacing the magnets the engine was running ok at low to medium rpm despite having 5 smashed magnets.
The stator looks fine and I have not touched the trigger so the timing should not have changed
Can anybody suggest a probable cause for the engine not starting.
Best regards.
Graham.
 

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: Flywheel magnets

Have you checked the resistance of the stator? Just because it looks good doesn't mean that it is working properly. You should be seeing 500 to 700 ohms between the White/Green and Green/White on the stator. Make sure you disconnect the wires from the harness when checking.
 

albert1

Cadet
Joined
Jul 16, 2009
Messages
9
Re: Flywheel magnets

Hi,CPO
Thanks, no I have not had the stator checked, how will the stator resistance prevent the engine from starting if I have a spark on all 3 plugs and the engine was runing ok prior to changing the magnets ? I have not touched the stator, so not sure how orwhy the stator should be an issue now, have only replaced 5 magnets, please can you explain further.
Thanks again,
Graham.
 

albert1

Cadet
Joined
Jul 16, 2009
Messages
9
Re: Flywheel magnets

Hi John,
Thanks, I will give that a try, but think I will take the flywheel back off to check the key has not broken off first, Do you think the new magnets being weaker could be the problem ?
Best regards,
Graham.
 

john from md

Commander
Joined
Apr 13, 2008
Messages
2,184
Re: Flywheel magnets

Anything is possible but here is what I know about ALNICO magnets, the type commonly found in the era these machines were made.

There are two ways to make them loose magnatisim; one by heating them real hot and the other is to pound on them with a hammer.

If you had to pound them out of the flywheels they came from, that could have weakened them but I doubt that you had to beat them that much.

You have a better chance of the key being broken or the plugs to the stator being incorrectly connected.

John
 

albert1

Cadet
Joined
Jul 16, 2009
Messages
9
Re: Flywheel magnets

Thanx John,

when I get the flywheel off I will double check the polarity of the magnets in case i glued them in wrong, maybe the timing is ok but the weaker magnets are somehow producing a weak spark, when I checked the spark it was in bright sunlight and so was hard to tell if the spark was nice and blue.

regards Graham.
 
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