Tohatsu M40 not charging

[Boatdrinks1965]

Hooked up battery backwards and motor quit charging. Replaced rectifier but still not charging. This was a manual start motor with the conversion kit added. Probably need to pull the flywheel but need to know what to look out for. Thanks

 

[Sea Rider]

Welcome to Iboats,

Check fuse, probably blown, check flywheel alternator if circuit is open, test both wires that comes down from alternator and provides electricity to the rectifier, probably was shot too when reversing baterry polarity.

Happy Boating

 

[Boatdrinks1965]

Fuse not blown. If I disconnect red wire from rectifier while running it shows 5 volts. Don't know what to check on the 2 wires coming from alternator. Should each have voltage? If so how much?

 

[pvanv]

The M40D has 2 alternator coils in series. What is the impedance across the alternator wires? Did you test the impedance across the replacement rectifier?

 

[Sea Rider]

Which M40 is it, 2 cylinder 40C or 3 cylinder 40D ?

Happy Boating

 

[Boatdrinks1965]

It's the 40d 2 stroke 3 cyl. 2 wires come down but I haven't taken flywheel off yet to get a look. Dealer tells me I need special tools and he's too far to tow it with my trailer. Should I have continuity between the two leads with it off and what should I have with it running? Any other possibilities before I tear into it? The rectifier is brand new and the wire going to the battery is good. I know very little about electricity. Thanks

 

[pvanv]

Alternator resistance should be 0.3 - 0.5 ohms using an ohm meter.

 

[Sea Rider]

No need to pull flywheel off just check impedance as suggested, will need to pull flywheel off only if alternator coil is found dead or altered. Paul is it possible to change just one coil or comes as a 2 coil pack ?

Happy Boating

 

[Boatdrinks1965]

So the 2 leads that go under the flywheel should read .3 to .5 ohms if I connect one lead to each? Are there diodes or anything else up there? Can't find a schematic anywhere for it.

 

[pvanv]

Yes, the resistance across the coil set should be read that way, of course when not running. The alternator coils come as a set only. Diodes are in the rectifier/regulator, not under the flywheel. Full diagrams are in the Factory service manual, available from your dealer.

 

[Boatdrinks1965]

No reading between two leads so I pulled the flywheel and one of the alternator plates is shot. Thanks for all your help and a final question. Does anyone know what the torque should be on the flywheel?

 

[Sea Rider]

Does anyone know what the torque should be on the flywheel?

Flywheel nut torque is : 88-108 NM (Newton Meter) 100 NM should be fine.

Happy Boating

 

[Boatdrinks1965]

Thanks again!