Replacing a Flywheel Magnet and Rewinding a Stator

[eSCHEn]

I've got a 25HP outboard here and I'm in a wee dilemma as to how to fix it given its faults. Here's a bit of back story.

It's a mid-nineties two stroke Mercury Sea Pro made in Belgium. It stood for about five years and started no problems when it was brought back into commission (not by me). Unfortunately towards the end of its 15 minute commissioning session it abruptly stopped and wouldn't restart. Problem was diagnosed to a cracked magnet in one of the coilpacks. This was replaced but the engine still wouldn't start and it's at this point I inherited it

The engine's symptom is no spark. Not a weak one, just absolutely nothing. There's two problems I can see causing this: (a) one of the flywheel magnets has broken off and (b) it's damaged a stator coil. Pictures show the damaged bits.


Now here's my dilemma. It's originally an engine that was more US based in sales by look of it. That means all the decent second hand gear is overseas. That makes is expensive to ship. The stuff over here isn't that good as the selection is small and that also makes it expensive. So I got to thinking; the only things actually wrong are a broken off bit of magnet and a damaged wire.

So what I'm thinking is to remove the broken magnet and replace it, probably doing the other side at the same time for peace of mind. The stator coils should be rewindable so that's what I'd do to them.

My only issue is that I've never done this before and never heard of anyone doing it. That generally means it's a less than stellar idea! So I'm looking for anyone who's done similar to what I'm thinking about and to ask:

• What level of success did you have?
• What was the cost like?

I'll be very grateful for any (useful, natch) responses to the above

 

[Tinbasherdan]

I cannot imagine they would go to the extent of making a completely different stator and pickup magnet just for one model, I would put money on it being interchangeable with another model, it's just finding which. Any merc dealers local? Or engine breakers? Or even tohatsu, I believe a lot of mercs under 30hp are built by tohatsu

 

[mart13]

I rewound a 3 phase bike alternator with great success.
You need insulated copper wire of the correct diameter and plenty of time and patience.
I made a plan/note of the pattern as i unwound the old wire and took loads of photos.
Once I understood how it was supposed to be it was quite easy if not time consuming.
Once rewound and tested for continuity i found (on the net) some aerosol insulation spray(3M if memory serves)and gave it a good coating with that.

 

[eSCHEn]

That's the problem I'm finding Dan, the model and its superseded numbers seem to be ones that were primarily US sales. The market is small over here and the quality isn't great.

It's a bit of beater cosmetically but seems sound enough internally. Has good compression etc. I want something reliable but not sure on the quality over here and don't want to throw parts on it that I'm not happy going out to sea in you know?

 

[eSCHEn]

I rewound a 3 phase bike alternator with great success.
You need insulated copper wire of the correct diameter and plenty of time and patience.
I made a plan/note of the pattern as i unwound the old wire and took loads of photos.
Once I understood how it was supposed to be it was quite easy if not time consuming.
Once rewound and tested for continuity i found (on the net) some aerosol insulation spray(3M if memory serves)and gave it a good coating with that.

You're braver than me I'd considered rewinding myself but had sort of thought a professional outfit would be where I ended up due to time. Good to know you had success though. What size engine was it? I think this one's about 450cc ish.

 

[Tinbasherdan]

That's the problem I'm finding Dan, the model and its superseded numbers seem to be ones that were primarily US sales. The market is small over here and the quality isn't great.

It's a bit of beater cosmetically but seems sound enough internally. Has good compression etc. I want something reliable but not sure on the quality over here and don't want to throw parts on it that I'm not happy going out to sea in you know?

If you can find a breakers, measure them up and ask if they have anything similar? I can ask a mate in America if you send me the part numbers, hes big into his boats and only uses merc, so he has a good relationship with the dealer

 

[pedrobedro]

We used JB weld to glue the magnets back in a bike flywheel and it's still going years later.

 

[Seadog]

From what I can make out in your picture the damage is confined to two turns of the coil. They're both on the same layer, so unlikely to make much of a difference, unless there is a break in one or both of the conductors. If not broken, and you gently pry them apart so no bare copper is touching then that will be sufficient. Also, the chip off the magnet I would not imagine to be that serious and ought to allow some spark, although perhaps not full energy at higher revs. Have you checked the points and the condenser? Is there continuity throughout the circuit. It doesn't look too difficult a rewind, I think you could do it by hand. If you need copper wire I've a fair selection so could probably help there.

 

[eSCHEn]

If you can find a breakers, measure them up and ask if they have anything similar? I can ask a mate in America if you send me the part numbers, hes big into his boats and only uses merc, so he has a good relationship with the dealer

Nothing local that I know of unfortunately Thank you for the offer re you mate - I'll let you know if it comes to that

From what I can make out in your picture the damage is confined to two turns of the coil. They're both on the same layer, so unlikely to make much of a difference, unless there is a break in one or both of the conductors. If not broken, and you gently pry them apart so no bare copper is touching then that will be sufficient. Also, the chip off the magnet I would not imagine to be that serious and ought to allow some spark, although perhaps not full energy at higher revs. Have you checked the points and the condenser? Is there continuity throughout the circuit. It doesn't look too difficult a rewind, I think you could do it by hand. If you need copper wire I've a fair selection so could probably help there.

Yes, it's just on the two turns shown as far as I can see. I'd never even thought of removing the continuity and just keep using it. The lump of chewing gum made me think - if prying them apart does work then I can make that fix robust and reliable by potting that small section with a lump of epoxy Thank you very much for the offer of wire, I'll see how the fix works and I'll let you know

The engine's currently at a mate's who had the right socket sizes (I've lost mine) so I'll get the bits back and see if I can put a fix in. At least that way I can hear it running and assess whether it's worth fixing further.

It's a CDI model so no points to check but I will be checking the output from both coils. As I said only one has been replaced and I suspect that both are gone.

 

[Gareth J]

As above, you should be able to effect a repair to that coil without a total rewire.

It's worth checking the rest both visually and with a multimeter to be sure there aren't other bits of damage.

Then, if it ends up being impossible to repair just by teasing apart, you could try cutting the wire and undoing a loop. This will give you access to more wire and let you put some heatshrink over it. You won't get it back so neatly as it sits now but so long as there is room for a bit of a carbuncle, should work fine, at least fine enough to get a good spark anyway. Less hassle than re-winding it anyway.

I also glued some delaminating magnets onto a lawnmower flywheel with chemical metal a while ago....ok so far

 

[mart13]

Hi again
sorry for the late reply
It was a Yamaha TZR 250.
I had nothing to loose as it was scrap before I started....

 

[eSCHEn]

Got the engine back today. It's been with a mate who had the pullers etc which I didn't.

So it's not looking good. The magnets have been reattached and the coil wires separated. Still absolutely no energy produced from the pull start when tested on the meter

As it could be one of a few things I think this engine has come to the end of its life with me. I need something more reliable for the places I'll be going with it. Will try and recoup some of the cash by flogging it but I don't think there's a great deal of value left in it.

Thanks to all who participated, your input is much appreciated

To the bay of fleas via the tree of gum, onward!

 

[Bill Edwards]

It's probably of no interest but you can get stators rewound. I've just had one done for somebody for a quad, £140 plus vat. Painful, but under half the cost of a new one.

 

[eSCHEn]

Thanks Bill, yes decided to not repair this engine and go for another. Just too many variables and I will be putting out of a very fast tided area so just want something reliable. Cheers for the info though :thumbsup:

Amazingly found a local seller with a nice old unit, 20HP and about as old as me

Fuel pump outer plastic split when me and the seller were trying to start it so not heard it run yet. Has good compression, turns freely and looks straight but tatty cosmetically. Now off to find a fuel pump