15 hp johnson high voltage charge problem

[efddd]

Hello,
I'm hoping for some help here. I have an unusual situation. Let me try to explain this. I have a 1979 15 hp 2 stroke that I use as a kicker on a salmon boat. It is an electric start model with a charging stator. Last year I decided to put a throttle servo on it to controll trolling speed. After I installed it I found that the servo motor was chattering and doing things it shouldn't. I called the mfr. of the servo unit and they said my charging system was emitting an electrical "noise". We tried shielding cables to the servo and all sorts of trial and error things and got nowhere. I ended up taking the servo control off and went back to controlling the speed with the tiller handle. Now I get to looking around and I see over the years Johnson has made several styles of ignition systems on these engines and they for the most part wwill interchange. I bought a ignition/stator setup from an 89 (10 years newer) thinking maybe they changed the electronics end of this enough that it may be worth a shot at getting rid of my "noise". I changed it all over. Got rid of the power pack mounted to the back of the block and changed out the coils and all of that biz. I started it and it fired right up and runs like a champ but when I checked the voltage output on the charging side of it the thing has like 20 volts idling and increases up to like 55 volts if you rev it up at all. I changed out the rectifier with the old one and have the same thing. Is my charging stator bad or what am I missing here ??? PLEASE HELP!!!
Thanks

 

[HighTrim]

Re: 15 hp johnson high voltage charge problem

The 89s are a bit new compared to what Im used to working on, but did it have a regulator?

 

[Fed]

Re: 15 hp johnson high voltage charge problem

Is it connected to a battery?

 

[efddd]

Re: 15 hp johnson high voltage charge problem

No it is not. I am reading with a meter at the plug to connect it to the battery.

 

[Crosbyman]

Re: 15 hp johnson high voltage charge problem

next step is to connect the battery and see how the charging circuit voltage across the battery is precisely.

Reading voltage across open connectors is not indicative of what the voltage will be when the stator output faces the internal resistance of the battery itself.

as far as "noise" is concerned you can try a fat capacitor across the battery itself (respect polarity !! ) A large capacity capacitor/condenser will regulate short battery fluctuations. If the noise is high frequency noise add a small capacitor across the big one. the small one will short out high frequency noises, the fat one will absorb/flatten short power burst . .

 

[Fed]

Re: 15 hp johnson high voltage charge problem

Connecting it to a battery will pull the voltage down & even the voltage out.

 

[WernerF]

Re: 15 hp johnson high voltage charge problem

The only thing that can be operated from the stator without a battery are incandescent lamps with the right power rating. Anything else is too sensitive to voltage fluctuations.

 

[gm280]

Re: 15 hp johnson high voltage charge problem

You can even install a heavy current type of induction coil to remove even more noise. Put the inductor in series with the battery and the capacitors parallel making a normal LC filter. The voltage you are reading is an open circuit voltage . Once you connect it to a battery (load) that voltage will certainly come down a lot. But remember, in order for the charging circuit to be able to charge a battery it has to put out a higher voltage then the battery voltage or nothing will happen. Capacitors allow AC or varying DC voltage levels to pass through while blocking steady DC voltage levels to pass and coils allow DC levels through while blocking AC varients to be blocked or increased resistances to them.

 

[efddd]

Re: 15 hp johnson high voltage charge problem

I hooked it to a battery and that part of the problem is solved. It reads 13 volts at idle and up to 15 at higher rpms.
You guys are awesome!! I hooked up the servo and still have the same thing though. If you hold the servo motor in your hand and get it anywhere within 6 inches of the engine when it's running it flutters all over the place up and down. It is reallly bad the closer you get to the coils. Unfortunately it mounts just ahead of the coils right in front of the starter. I'll try the capacitors and see if that works next. If anybody has any other ideas I'm all ears. I'll be back with results. Thanks to all !!

 

[gm280]

Re: 15 hp johnson high voltage charge problem

Are you totally sure the problem is coming from the supply voltage and not via RFI? Reason I ask is because you stated that it gets worst if you put the servo closer to the coils. SO maybe it isn't all supply voltage problem. Try sheilding the servo with some type of metal shield around it and see if it improves the servo operation. If it does, you may need to build a shielded container or box of some sort to install the servo in...

 

[efddd]

Re: 15 hp johnson high voltage charge problem

I wish I knew for sure. I already tried the shielding thing. Tried shielding the servo itself, the cables, sepeateing all of the servo wiring from power wires and everything else I could think of. No luck with anything I tried. I guess I'll give up on it and go to a vernier type cable or something.