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Exciter voltage

J

Jen

Member
I read a post on these forums that exciter coil voltage should be about 100 V AC and have some questions.

My motor is a 1999 BF25A, electric start, remote. I am getting a no spark situation. The exciter was slightly out of spec resistance wise and the CDI matrix made me think the CDI was bad

I bought a parts motor that had spark when I bought it. We tested before buying.

I moved the CDI over to my engine and oddly, no spark.

The Bl/r wire is good and disconnecting it does not help

I moved the exciter over from the parts engine.

Am I really supposed to get 100 V AC from the green and black wire from the exciter when cranking the engine (not running)?

When putting the flywheel back on, am I supposed to do anything special other than torquing the bolt properly?

Thanks for all help.
 
I am not sure what the exact output is, but it should be somewhere around 100 vac peak/peak.

Just put the flywheel back on and tighten to 83.2 ft/lb.

If that does not get you spark, have to check the resistance or output from the pulsars under the cam shaft pulley?

Mike
 
Hi,
Welcome to the forum. Sorry you're having problems.

I don't know this outboard but I just wanted to say that, since you've got the parts and are already doing "swapnostics", try using the flywheel from your parts motor too. This would eliminate the possibility of the magnets in your old one being weak. Especially since you know that combo of coil and flywheel produce spark.

There shouldn't be any problem putting the flywheel back. The crank end is keyed so it only goes on one way. This is all dependent on, of course, if your parts motor is an exact match to your outboard.

Hopefully someone else here has better suggestions for you.

Good luck and let us know how it's going.
 
jgmo said:
Hi,
try using the flywheel from your parts motor too. This would eliminate the possibility of the magnets in your old one being weak.
Click to expand...

Thanks. The magnets on my old flywheel feel a bit stronger than the parts engine. I'll try your suggestion and report back.
 
Also check the circuit it may be down to earth , it is recommended you disconnect the kill /stop switch wires for the time being while you are trying to find the fault .once you have spark then reconnect the kill switch wires a faulty kill switch will cause a no spark too
 
you mentioned electric start you also have to check for down to earth on the ignition , easy way is to disconnect the 2 wires from the exciter coil with the meter place one terminal into the terminal where the exciter coil wire plugs into the other terminal onto a good earth do this on both terminal and check if your circuit is down to earth disconnect the battery cables .then turn the key to the on position and do the down to earth test
 
Last edited:
Tegweni said:
you mentioned electric start you also have to check for down to earth on the ignition , easy way is to disconnect the 2 wires from the exciter coil with the meter place one terminal into the terminal where the exciter coil wire plugs into the other terminal onto a good earth do this on both terminal and check if your circuit is down to earth disconnect the battery cables .then turn the key to the on position and do the down to earth test
Click to expand...

Oh, interesting. I will check.
 
I disconnected the exciter plug to the CDI and tested the two contacts on the CDI plug side to ground.

With the remote and battery disconnected;
The green wire is 2.3 Mega ohms
The black wire is pretty much 0 ohms.

With the remote connected but not battery connected and ignition on;
Green is 2.3 Mega ohm
Black is still pretty much 0 ohms.
 
Honda uses black as earth .to me it seems ok other members may know better .You can determine what voltage your exciter coil should produce at start up measure the amps and resistance V = I X R as you mentioned the resistance will vary depending on the heat ,using this formula will give you a +/- volts your exciter coil should produce to start
 
Good ? just to give you a rough estimate Yamaha 25 hp cranking at 1500 rpm produces 110 V we will find out what yours need to produce.Also check your plug leads.
 
You have 3 cylinders the ignition system works on a capacitor discharge system triggered off by the pulsar it goes through a diode which is like a one way street if the diode has packed up it wont spark either.
 
I think the suggestion of testing to ground is to check to see if the exciter has an internal short to ground. You do not need to get too deep in the technicalities of ohm's law.

You still have not said if you have any voltage output between the black and the green lead coming from the exciter. If you have no voltage there, the exciter has an issue or the flywheel has an issue. There isn't anything else in the circuit at that point.

If you have voltage there, then check the voltage from the pulsars. Those voltages will be very low, generally around .5v ac peak voltage. Blue/Yellow to Black, Blue to Black and Blue/Green to Black.

When cranking the engine to test these voltages, be sure to have the spark plugs removed. The flywheel will turn faster and voltages will be higher.

If you have voltage from the exciter and voltages from all of the pulsars, then check continuity in the wiring harness from the exciter and pulsar connectors to the cdi.

Be aware, if may be possible that your voltmeter is not sensing the voltages quickly enough and may just be giving you erratic readings.

If all the above fails....put the working parts back on your parts motor and measure the voltages on that motor. That will show you exactly (are at least super close) to what you should be seeing with the meter that you are using.

Mike
 
I get 22 V AC measuring across the green and black lead coming from the exciter using a Fluke 115 with the engine cranking by the starter on a charged battery.
 
The dva is a add on you can get one for around $30 or just make one. It is a capacitor with a resistor and diode. The capacitor stores the peak voltage so you meter can read it. The resistor bleeds the voltage down so you dont get bit when you disconnect the leads.
 
Thanks for the info about a DVA. Pretty sure my meter gives me peak voltage.

The exciter is putting out 22 Volts AC. It's resistance is between 200 and 220 Ohms depending on temperature. The manual says resistance should be 272-368.

If the exciter is putting out low power does that mean the CDI should be putting out weak or intermittent spark or is there a cut off?

I have been all over the schematics but there is a processor in the CDI that does timing advance and they don't give any details of what else the processor does.
 
According to the splecs on your Fluke...it measures true RMS voltage. Theoretically, to get the peak voltage from rms, you multiply the rms voltage by √2 or 1.414. So your peak voltage "theoretically is 22 x 1.414 = 31.108v.

Reading in the manual, it says that there is a voltage doubling capacitor in the cdi circuit. I can not see it in the diagram. As for the timing, it is advanced based on the speed of the engine, and there is a separate circuit in the cdi that varies the action of the pulsar gate circuit.

Bottom line.....since I have never had an spark issue with any 25HP, I can not say for sure what that voltage should be. The 35 - 50 HP are around that 100v mark.

Anyway....with all that theory....you still have that parts engine. Put you old exciter back on that motor and see what various readings you get. If the voltages are the same in both engines, then, the voltage is probably fine.

If the pulsars are in question....other than testing output, I have verified a faulty pulsar or timer base (on Evinrudes) by disconnecting the pulsars and connecting a 1.5 v battery to one set of the pulsar leads going to the cdi through a momentary switch. Assuming the exciter voltage and the cdi are good..... if you intermittently activate the switch, while cranking the engine, it applies 1.5v to the leads (simulating the pulsar output). There should be a spark at the corresponding coil - every time you push the switch.

Anyway....hope I did not lose you in all that extra stuff.

Just check the voltages on that other engine.

Mike
 
i have a Suzuki 4hp in good running order with the DVA meter i get 18V pull starting , your reading of 22v is not far off being electric start .
 
hondadude said:
According to the splecs on your Fluke...it measures true RMS voltage. Theoretically, to get the peak voltage from rms, you multiply the rms voltage by √2 or 1.414. So your peak voltage "theoretically is 22 x 1.414 = 31.108v.

Reading in the manual, it says that there is a voltage doubling capacitor in the cdi circuit. I can not see it in the diagram. As for the timing, it is advanced based on the speed of the engine, and there is a separate circuit in the cdi that varies the action of the pulsar gate circuit.

Bottom line.....since I have never had an spark issue with any 25HP, I can not say for sure what that voltage should be. The 35 - 50 HP are around that 100v mark.

Anyway....with all that theory....you still have that parts engine. Put you old exciter back on that motor and see what various readings you get. If the voltages are the same in both engines, then, the voltage is probably fine.

If the pulsars are in question....other than testing output, I have verified a faulty pulsar or timer base (on Evinrudes) by disconnecting the pulsars and connecting a 1.5 v battery to one set of the pulsar leads going to the cdi through a momentary switch. Assuming the exciter voltage and the cdi are good..... if you intermittently activate the switch, while cranking the engine, it applies 1.5v to the leads (simulating the pulsar output). There should be a spark at the corresponding coil - every time you push the switch.

Anyway....hope I did not lose you in all that extra stuff.

Just check the voltages on that other engine.

Mike
Click to expand...

Thanks Mike. My pulser coils are giving me 0.5 volts which I guess I should multiply buy 1.414 because of RMS so about 0.7 volts.

Looks like I have some fiddling to do.
 
Mike. I am just about to get back into the motor.

I bought a DVA which gave me the same voltage output on the exciter as my Fluke did which is 22 volts. Seems awfully low to me.

Jen
 
So we have spark, consistently. It feels weak to me but I think it is right for Honda CDI.

The exciter measures about 200 Ohms so slightly out of spec. With a DVA I am getting 35 V on a decent crank speed. I have ordered a new coil from a newer Honda outboard that uses the same flywheel . They seem to be calling exciter coils "power" coils now. Is that correct? The new coil should be here next week.

Yesterday we nearly had start. Was definitely firing a couple of times. Today we rebuilt the donor engine's carbs and tried that on the engine but no joy. Now we are rebuilding the engine's carbs to give that a try.

We tested the fuel pump by removing the output hoses and cranking. Fuel came out so I think that is good.

We checked the timing belt is right by aligning the cam shaft marks then looking at the flywheel marks and they line up.

One of my neighbours here has a BF40 and told us that he sometimes has to drain the float bowl. I wonder if I am pumping too much fuel into the float bowls by squeezing the priming bulb until it is hard.

Would love any thoughs. As a reminder, this engine was running then the previous owner said the CDI unit died. They took it to a mechanic who said CDI and exciter were out of spec and since they could not buy replacements we got the engine. We then bough a parts engine with a good CDI and checked spark on the parts engine before buying. I swapped over the CDI and we now have spark on the main engine. This is a BF25A with remote. We have the remote plugged in but no gear or throttle cables rigged.

Cheers
 
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