Tohatsu M-18A Battery charging.

[Bote]

I own a early eighties Tohatsu M-18A 2 stroke. It comes with 2 pin electrical plug for running lights.
I believe that I need some kind of rectifier to charge battery for electric motor.
Does it need to be a Tohatsu rectifier or one from electronics store will work as well ?

 

[pvanv]

Re: Tohatsu M-18A Battery charging.

Yes, you need a rectifier to do charging; The alternator's raw output was intended to supply lighting (only) as is, and can be rectified into DC for charging.

That motor's an oldie. I don't even have a parts manual that goes back that far, so getting an exact Factory rectifier may be a problem. The p/n 34676-1601M (now superceded to 346761602M), which is the rectifier for the 8B thru 40C motors should work. There are still a few available from the factory, at a price of $95.95.

However, as an electronics engineer, I can say that any suitable bridge rectifier of adequate rating (and equipped with adequate cooling) will work. Since that alternator probably makes at least 5 amps, you will want a unit that can handle say 10 amps or so.

 

[Bote]

Re: Tohatsu M-18A Battery charging.

Thanks Paul.
Motor is an oldie but goodie. Despite its age runs like new.
Alternater is rated at 6amps (info from old japanese website).

 

[Silvertip]

Re: Tohatsu M-18A Battery charging.

Keep in mind before spending money on the charging system that at 6A output, you would need to run wide open for hours to add a significant charge to a trolling motor battery. Look at it this way. A trolling motor (50 - 55# thrust) draws in 40 - 45 amp range. If you ran the motor for two hours you would suck 80 - 90 amps from the battery. To replace that divide 80 or 90 by 6 and that would be roughly the amount of time it would take to replace that used energy. Hardly worth the effort. Install an on board charger and plug in at the dock.

 

[Bote]

Re: Tohatsu M-18A Battery charging.

Yes, it hardly makes sense.
I may just stick to original purpose and just run the boat lights.
Thanks.