78 Johnson 70hp not charging?

ogishere · Apr 1, 2007

I dont think my engine is recharging the battery. The Tach quit working , I dont have a reading on the tach signal wire at all. The battery reads 12v with motor running. How do I test the charging system? What would be bad? I have another motor just like it so parts is not a problem.

Thanks in Advance
ogishere

R.Johnson · Apr 1, 2007

Re: 78 Johnson 70hp not charging?

More than likely it is the rectifier, but when you change it, check the battery connections. If it has wing nuts', replace with brass, or stainles steel nuts'.

ogishere · Apr 1, 2007

Re: 78 Johnson 70hp not charging?

Where is the rectifier located and what does it look like? Im kinda new to boat motors. Already use stainless steel on battery. Is this hard to change?

Thanks
ogishere

ezeke · Apr 1, 2007

Re: 78 Johnson 70hp not charging?

Your rectifier should be cylindrical, with a triangular base. It would have 3 or four wires connected to the terminal block near the flywheel. One of the other wires at the terminal block is/should be gray. The gray wire is the pulse wire that sends the signal to the tachometer.

If you go to the BRP parts catalogs and look up your motor, you can then open the "ignition" diagram and see the components:

http://epc.brp.com/default.aspx?brands=ej&lang=e

You might want to read this thread, where Joe Reeves describes how to test the rectifier. It is near the end of the thread:

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=28;gtid=1290805

ogishere · Apr 1, 2007

Re: 78 Johnson 70hp not charging?

ezeke said:
Your rectifier should be cylindrical, with a triangular base. It would have 3 or four wires connected to the terminal block near the flywheel. One of the other wires at the terminal block is/should be gray. The gray wire is the pulse wire that sends the signal to the tachometer.

If you go to the BRP parts catalogs and look up your motor, you can then open the "ignition" diagram and see the components:

http://epc.brp.com/default.aspx?brands=ej&lang=e

You might want to read this thread, where Joe Reeves describes how to test the rectifier. It is near the end of the thread:

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=28;gtid=1290805

ogishere · Apr 1, 2007

Re: 78 Johnson 70hp not charging?

Thanks alot this helps tremendously!!
will try it out tomorrow!

Thanks again
ogishere

ogishere · Apr 3, 2007

Re: 78 Johnson 70hp not charging?

the rectifier was bad. I had an old one on a donor motor but the wiring is dry rotted. Any suggestions on where to order one online? Iboats.com dosent have one. I found one on ebay for 19.99 it has the same numbers as the one I have. It also has a 14 day warranty on it so I think I will order it, only thing is it is used so I dont know how long it would last. Do these go bad pretty often or do they normally last a while?

Thanks for all the help!!
ogishere

tashasdaddy · Apr 3, 2007

Re: 78 Johnson 70hp not charging?

they rarely go out. just touching battery cable backwards can blow them tough.

ezeke · Apr 3, 2007

Re: 78 Johnson 70hp not charging?

I would not buy an unregulated rectifier on Ebay. Too often they have one bad diode.

These will work fine:

http://www.iboats.com/mall/partfind...ow=69&keywords=rectifier&session_id=443726537

http://www.iboats.com/Cdi_Rectifier...55660691--list_time.1175628135--view_id.47460

Some of the old ones have a ground wire. The new ones don't because the case is already grounded to the engine block.

ogishere · Apr 3, 2007

Re: 78 Johnson 70hp not charging?

Alright thanks I will just order the one off ebay today!
Trying to get boat ready for first outing this weekend I dont know who is more excited me or my 11yr old son!
probably me!

thanks again this board has been a God send!!!
ogishere

tashasdaddy · Apr 3, 2007

Re: 78 Johnson 70hp not charging?

did you know there is a cold front coming thru. suppose to be 40 here sat morn.

ogishere · Apr 5, 2007

Re: 78 Johnson 70hp not charging?

Your right to cold this weekend, I will have to wait maybe next weekend? hopefully! ordered a rectifier through Johnson dealer will be here Monday so I have to wait til next week anyway. My son cant wait he calls the first outing her maiden voyage and named the boat Old Glory! He loves fishing and being out on the lake. We camp alot. Glad the season is back! d

sweetmarie · May 13, 2007

Re: 78 Johnson 70hp not charging?

R.Johnson said:
More than likely it is the rectifier, but when you change it, check the battery connections. If it has wing nuts', replace with brass, or stainles steel nuts'.

Hi, I'm not doubting your suggestion but why do wing nuts not perform as well as s/s? I'm sure you're going to tell me that wing nuts promote corrosion and loss of contact, but why? I currently have a wing nut on the positive terminal, the wing nut is in good shape so far, been there a few years although I did have to clean the contacts at the end of the wires at times. Do they make s/s wing nuts? Thanks
ps: I recently changed my r/r, wasn't charging.

78 Johnson 70hp not charging?

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