Regulator blown

Hello

I have a Yamaha outboard, F80 model year 2002. The actual type and serial is F80AET L 1000795 Q

The regulator seems to be blown and sends 17V to the battery depending on revs etc. Only on very low revs, idle, do I get 13.8V. Anything over that and we see the voltage increasing up to 17+ V.

A few weeks ago I disconnected the negative terminal from the battery while on a short trip trying to save the battery from abuse. Bad idea as I did not have engine trim and the engine instruments were showing rubbish. When I reconnected the battery, it miraculously started working again at a stable 13.8V or thereabouts, regardless of revs.

I was told that rusty connectors do that, and I thought my action of removing the terminal and reinserting it did the trick. In addition I later filed, cleaned and polished the terminals and the battery is also brand new.

5 weeks later and daily use of the boat, I was telling a friend the story, how I fixed the overvoltage problem with cleaning the terminals, and as I revved the engine to show him, I saw 15+ Volts.

We measured the voltage on the engine and the problem seems to be the regulator. As it is hard to find a replacement in short notice, it is not a piece stores stock, and it is holidays now here in Greece, is there a trick I can do to preserve the battery?

Each battery pole has two leads to it, a thick and a thinner one. The thick lead I presume drives the starter motor. But does it also charge the battery? Then once started I could remove just the thick lead.

Any suggestions welcome.

No 'trick' except replacing the regulator....

FWIW, it is ALWAYS a bad idea to disconnect any major connection with the engine running, especially a main battery connection.

As far as how the battery is wired, best to check your manual.....sometimes the installers will make adjustments so its hard to say without actually being there to see it.

Hello

One thing to note is that while on many cars, in my experience, when the regulator blows it stops supplying the rest of the car, and you are running on the battery for a while, until the battery dies too. So you can drive your car for a while and nothing major happens to the car and typically you take care not to switch too many things on to preserve the battery. This is all so common.

But on this Yamaha engine, the regulator has gone in a destructive way allowing large voltages through, and while I was worried about the battery alone, thinking will it take this increased voltage, I did not think that the engine itself might also have a problem with 18V. Because I had mistakenly thought that noone would built an engine that will self destruct. But it did have a problem it seems, yesterday it stopped working, and now we think it is also the CDI unit that has also blown on account of these large voltages.

Quite upset now as there are a few more days of holiday left the weather is the best ever and I have no boat. Not happy with Yamaha.

The cdi probably went as a result of disconnecting the battery while running..That is a no-no on any outboard engine...the cdi may not be blown though...have you checked to see if you have voltage to it..you may have a blown fuse..

I have checked all the wires I could, there were only two fuses present, a 30A and a 20A, and they are OK. I doubt the CDI draws 20A or 30A anyway. I could not see any other fuses anywhere. Is there an easy way to determine whether the CDI is working, off board?

have you checked spark with a gap tester?

Yes on 2-3 spark plugs, there was no spark. It behaves as if the quick stop is not inserted.

OK so we tried to take off the flywheel - absolutely no way, to me it looks as if the nut hodling it down is fused onto the shaft, I do not think anyone has ever removed that nut since 2002 in some factory in Japan when the motor was built. Strangely I also paid a hefty sum two years ago to have the timing belt replaced, may be he replaced it without removing the flywheel...

The next step inserted the multimeter on the connector that connects the stator to the regulator (it was three wires I hope it was that) and measured AC voltage while cranking the engine. On 2 or 3 combinations (the connector has 3 wires) it read 5-6V AC while cranking. I took that to mean that the stator is producing some voltage and has not melted.

I also measured on the wires leading to the coils and saw no voltage so the fault must be the CDI.

Unfortunately the CDI seems to be outrageously expensive in Greece and must be brought in from abroad (no idea where) and costs something like $1000 whereas on US web sites the part is listed at around $340.

One problem is that the US sites do not list my type of engine, mine is a F80AET and the US sites list a slightly different designation.

Therefore the rectifier is 67F-81960-12 and on the US sites it is 67F-81960-12-00 - this looks the same so so far so good.

On the CDI the part is 67F-85540-01 and on the US sites it is 67F-85540-03-00 - this looks to be slighly different.

Update: The timing belt is new according to someone that knows and can be replaced without the flywheel coming off.

Just to repeat the sequence of events:

1) Voltage reading reads too high, reaching 16V and flashing on the instruments
2) Disconnect battery negative terminal and use engine for 20 minutes while on a short journey. Battery poles are brand new but wire connectors are quite rusty.
3) Reconnect battery negative terminal and re-tighten the wing nuts. Miraculously voltage reading now reads a perfect 13.8-14.2V while engine is running.
4) Boat is being used thus for 5 weeks.
5) Suddenly one day voltage reading again starts to increase, eventually exceeding 17V. Instruments flashing. Tested voltage on battery poles with multimeter and it agrees with the instruments.
6) Decide to disconnect the positive battery terminal to "save the battery from this abuse". Engine drives OK for about 3 minutes and then stops and does not start again. As if I had removed the kill switch. There is a definitive smell of burn from the engine but even with the cover off, we cannot identify the part.
7) There is no spark at the plugs. There is no voltage detected before the spark coils (assuming the meter would detect a voltage pulse).
8) Whilst cranking the engine I detected 6V AC coming to the rectifier's connector from the stator - three wires in total. I am assuming there is "life" in the stator and maybe it has not melted.
9) Everything points to the CDI. Or maybe, complete destruction of the Rectifier/Regulator that has the side-effect of not letting the engine start at all?