Charging system voltage

[Gamerse]

Can someone run out to their boat with voltmeter, and measure the voltage while its running. Don't care which model, must be two-stroke, non merc, 717 engine prefered, but I'll take almost anything at this point.
I've never measured a seadoo product's running voltage before, but I'm pretty sure mine is wrong. I just need to know I'm not crazy and this isn't just some weird seadoo thing. Anyway, just let me know what it does, and what the voltage is.
:cheers:
Ernest

 

[CaptSteve]

There is no correct voltage when the boat is running. All the regulator does is limit the voltage to less than 14.5 - 14.8 volts. The output of the magneto is AC current and is changed to DC current by the rectifier. You should normally see voltage from 12.5v to <15v when the boat is running.

The reason you can not get a constant reading is that when the boat is at idle the magneto may not produce 12v. However, what you will measure is the battery putting out ~12.5v. When the engine revs higher, what you read is the voltage coming from the magneto and regulated down to no more than 14.8v.

The battery gets charged because the magneto is putting out more current (amps) then is being used by the system. With the engine at 5500 rpm, you should read about 5 amps and 12.5v - 14.8v at the battery. If you read more than 15v at any time, then the regulator is bad.

 

[Gamerse]

^Thanks for the explanation. I am well aware of how things "should" look, I just needed confirmation that seadoo isn't using any weird trickery that would cause the bad readings I am getting. (the schematics say they are not) IE voltage changing faster than my dvom can read. Since idle speed out of the water is about 3,000rpm, and my starting voltage is about 12.5, the stator should be excited and producing power. I am at the point that I belive I have a bad stator that is not producing any power, or is shorting. The low voltage and intermittent shorts account for mpem resets that would require key removal and reinstallation. (also blown charging fueses but not mpem) All this adds up to why the longer the boat sits, (surface charging) the less often it dies, or why shutdowns may or may not occur more often at higher throttle. My boat was equipped with a full size battery set-up before I purchased it. While this is great for adding accessories, (I currently have none) it is overkill for normal operation. I think it is masking the low voltage that I should have noticed a long time ago, by having enough reserve power to run the mpem at minimum voltage without charging. I didn't have time to test that theory yet as I only gave myself an hour to work yesterday. The only other option is the mpem itself is shorting, as I will have removed all other circuits during this next round. That doesn't make a whole lot of sense though as shorting badly enough to affect readings at the battery, would surely draw more than 5A and pop the mpem fuse. I'm off to charge the battery and retest.
p.s. steve, your avatar, keeps interrupting my thoughts....
:cheers:
Ernest

 

[CaptSteve]

Hum, very curious. If I understand it correctly, when you put a voltmeter on the battery, the voltage is not constant, but quickly changing. You also say you are blowing the 15A charging fuse, but not the MPEM fuse.

If this is correct, there are a couple of things to check. In order for the rectifier to produce a solid voltage, it needs a good ground reference. You should check the ground leads in the rear box. This is where the battery connects to the solenoids and then the starter. If the ground is loose, or corroded, you could be creating a higher amp load as the voltage drops. If load is constant, as voltage drops, amps increase. You could also check the ground lead on the engine as this is where the rectifier gets its reference from. Are you having any issues with starting, this could also point to a poor ground.

I agree, if the MPEM was shorting, I would expect the MPEM fuse to blow. It sounds more like a charging system problem since that is the fuse is blowing.

I believe in 1996 the regulator/rectifier was a separate unit. In later years Seadoo put the rectifier/regulator into the MPEM. You could try disconnecting the regulator/rectifier and see if the voltage is still bouncing around, since you would only be running on the battery.

Let us know what you find.

 

[Gamerse]

Yea, basics have been covered, repeatedly. My particular boat is not grounded by the engine, it has it's own seperate ground cable. Everything else is grounded to posts in the grey box. I'm starting to consider multiple problems as an option.

I already tried disconnecting the stator and rectifier/regulator last week on the water and no change. I wanted to call it a bad or dirty crank trigger at that point, but I can't confirm without a labscope. Then I thought to myself, if it is not charging, then low voltage, blah blah blah see above post.... So I top charged the battery. (charger claimed 44% before charging) With a hot battery, retested, same results. I noticed the battery charger had a lazier digital meter, so I left it connected to monitor voltage. During the test, the mean never dropped below 12.2V after stating. So the mpem should have had plenty of power available.

This is one of those puzzles that I've been right on top of, but not quite able to crack. I think the last thing I can do at this point without a scope, is remove the magneto cover, peirce probe trigger wires as far back as I can, and check continuity while shaking them. Beyond that, it is a matter of flipping a coin and replacing the magneto or the mpem. Both have their merrits, mpem is easier to replace, magneto is cheaper...

:cheers:
Ernest


Electrical sidebar:
When we have corroded ground wires, the reference voltage doesn't change, so the current will only be lower due to the high resistance.

A ground can never cause high current draw. (when correct electrically, not talking about it somehow causing a short)

If the ground is loose, or corroded, you could be creating a higher amp load as the voltage drops. If load is constant, as voltage drops, amps increase.

Grounds are behind the load, high resistance to ground will only lower the current draw, because the reference voltage does not change. If there is voltage on a ground wire, it is not grounded, or completely grounded.

Thank you for the epiphany though, the charging system fuse is blowing, which means high current. If we apply the path of least resistance, the only possibility is a shorted rectifier. If this is true, the mpem fuse would not blow because it is in parallel with the 15A charging fuse. That I can test with the dvom and get it out of the way.

Sigh, more testing......

Thanks Steve!

 

[Gamerse]

Get ready for this, with nothing but the mpem connected and grounded, the voltage still spikes..... I disconnected everything not required to make the mpem function, and with it isolated, the voltage still goes crazy after start-up. The rectifier/regulator is junk as well, it's shorted internally. I'm at a bit of a loss. The component that produces the power is unplugged, and the meter is reading spikes of 18VDC+..... The wires pass continuity checks, and the rectifier/regulator is out and in my hand. The only thing I can think of is the stator is shorted internally, but how in the hell is it spiking positive voltage? The meter doesn't lie, (if it does I'm gona spike it into the river) and I'm getting AC readings under the same weird conditions....
Anyway, I'm not ready to call the mpem bad, it is just reacting to the voltage spikes by shutting off the engine. That is normal operation. I'm going to order a rectifier, at least it is confirmed bad, maybe it will be able to get this craziness under controll.... How I wish for a 787s electrical system lol.....
:cheers:
Ernest

 

[Gamerse]

So for all that followed me through this, drum roll please...... Wrong spark plugs! This is a case of new school electrical thinking overriding better judgement. The boat came with non-resistor spark plugs. I have used non R plugs in a lot of other engines, but I knew Rs were recommended in the FSM. I let my electronic ignition thinking get in the way the old school magneto ignition basics. Magneto systems "generate" the required power independent of everything else, so they are their own electrical circuit. With that being said, seadoo did not install any EMF protection anywhere in their system, relying completely on the resistor plugs for voltage spike management. When the non-R plugs were installed, the EMF field had nowhere to go except the surrounding wires. The spikes cause intermittent MPEM overvoltage protection.

The answer was on my mind the whole time! I just could not bring myself to believe something like that would cause huge voltage spikes. I just happened to have a pair of used NGK BR9ES plugs left over from the STS's last service. With every other variable eliminated, it was either a magneto problem, or the plugs. Which one was easier to try? The plugs of course. So, I changed out the B9ES plugs it came with for the BR9ES plugs, and the spikes were gone. I confirmed by switching back and forth. B9ES plugs=random over voltage spikes. BR9ES=steady voltage and a happy mpem.

I launched and celebrated with a few happy spins. I convinced my Mom to hop in for the first time and we took a 25 minute flawless test drive.

The rectifier/regulator is still dead. Its demise may be related to the spikes in the system. I'll have one on order as soon as I save a buck or two. Until then, I'll be enjoying the end of the season electric car style, charging every night.

Thanks to everyone for helping me keep my gears turning!


:cheers:
Ernest.