C.D.I unit blow up

[Gert Geyser]

Good day Gents
The C.D.I unit of my 100F Yamaha four stroke blow up and in the process damaged the wiring harness and also destroyed the Top cowling. The motor has done only 208 hours. Does anyone know why this might have happened? This is the first time I have had problems with this motor.

[CatCam]

Make sure your Voltage regulator underneath the CDI didn't overheat.....that's what happened with my 2004 F90 Four Stroke. When the Voltage regulator "Fried" it actually melted the CDI..... I was lucky and it didn't do any other damage.

The only other recipe for this kind of damage is some type of fuel leak.....

[Searider]

can confirm - also thought my CDI blew up this summer but indeed it was the regulator which developed such heat that one corner of the CDI started to melt ..

[Gert Geyser]

Thanks for the reply guys. So it will be wise to renew the regulator as well?

[CatCam]

Remove the Voltage regulator - it is easy. The regulator is mounted with the aluminum cooling fins facing toward you. If it fried you will see it when you take it off and look at the backside of it.....it'll be burnt to a crisp even though the front of it looked okay.

Many people don't know this but one of the main reason your voltage regulator goes out or FRIES on you is loose wing nuts on your cranking battery. NEVER use wing nuts on your cranking battery!!!! Ask me how I know this

[Searider]

Thats how my rectifier looked liked from the back and the place at the block where the CDI is located .
The cooling fins at the outside looked like always - nothing to see but I was quite surprised when I took it off and saw the rear side ..
The damaged rectifier blew a main fuse so that I could not start anymore . Looking at the melted CDI and motor did not start my first thought was as well that the CDI was fried .
I disconnected the rectifier , replaced the fuse and motor ran well on battery power .
Merry x-mas !

[CatCam]

Searider - that is exactly what happened to mine. I was told that my wing nuts on my cranking battery came loose while I was running. This "freaks out" the voltage regulator because it sees a fully charged battery, then a millisecond later it sees a battery that needs a full charge -- this vicious cycle goes on and on and finally the regulator gives up the magic blue smoke.

And when it goes it takes other expensive parts with it. Did you ever find out why yours bit the dust?

Gert - did you pull the regulator yet??

[Searider]

No I don´t know why my rectifier failed . All connections etc were good .If you´ll search the net you´ll find that many failures like t´his happened and Yamaha came up with another rectifier (or changed the supplier ??) which should be more reliable ..
So far my new rectifier does the job .

[rodbolt17]

typical cause of regulator smoke is defective cables,cable connections or a bad battery.
ya should have seen some of the V6 looper jonny/rude water cooled regulator fires.

[Gert Geyser]

Hi Guys

Just read your replay, stripped the regulator and as you have suspected I found the regulator damaged as well. I will go through the wiring for bad connections tomorrow but in the meantime I did find a green wire with white line on the regulator that was not connected to any other wire is this correct?
Thanks alot for your help and a Merry Xmas to you all.

[Gert Geyser]

Hi Guys

Could not wait till tomorrow so I did check the wiring and found that the negative battery terminal was totally loose, so I think I have found the cause of the problem. I have learnt a very expensive lesson now as boat parts and repairs in South Africa are extremely expensive, I will make sure to check the wiring every time before going boating in future.
Once again thanks for the help.

[rodbolt17]

these regulator/rectifier assy's are not as sophisticated as the ones in your automobile.
most smaller outboards(under the 150 range) typically rely on air cooling.
the stator always puts out voltage when the flywheel rotor is spinning.
once the rectifier converts this AC voltage into a DC voltage the regulator takes over.
the stator on the F100 is capeable of about 60 volts and a current capeability of about 40 amps.
this current and voltage MUST be dropped to a useable figure.
this is the regulators job.
what current is not used is shunted to ground and is bled off as HEAT.
NO current path means NO heat dissapation which leads to letting the smoke out of the circuit.
doesnt matter WHAT part of the current path degraded.
internal cable failure,connector terminal to cable failure or terminal to block,starter hot feed or battery terminals or a bad battery.
there are a couple ways to make AC voltage/current.
larger coils of wire, stator size is fixed.
more magnents in the rotor, physically impossible.
the speed that the magnents rotate around the stator coils.
that is the big variable on an outboard.
it has to work with a rotational speed from about 650 RPM to 6000 RPM with no pully speed reduction like automobiles have.
in fact most automotive rotors are underdriven by 2-3 times crank speed.
thats an old street rod trick good for another 5-10 HP.
whan in your car,when was the last time you ran it with a crank speed above 4500 for an hour or three?
maintanence, pay now or later.
operators choice.

[CatCam]

Rodbolt17 - Thanks for all of your info on this forum. To be honest with you I think I really missed my calling in life to be a outboard motor technician like you....I am a mechanical engineer by profession but I always had a thing for outboards and keeping them running. All of your explanations are extremely informative and I really have learned a bunch of info from your posts.

Gert - sorry about the burnt regulator/CDI/cowling. It stinks that you are way down in South Africa and parts are so expensive there. As far as the internal parts, I would see what boats.net can do for you. The CDI and regulator are small parts so shipping shouldn't be too much. As far as the cowling goes, check and see any cross compatible cowlings, will a F90, F80, F75 fit the F100? If so, check E-bay to see if you can get a used one or check a boat salvage yard to see if they have a used on laying around.

Here is a listing that stated the 80, 90 & 100 cowlings are compatible.....: http://www.ebay.com/itm/USED-YAMAHA-...d462c9&vxp=mtr

Good luck to you, take care and Merry Christmas.

[rodbolt17]

started on a mechanical engineering degree decades ago, life got in the way.
got an equivalent associates degee in electronics courtesy of the USN.
got my disability from the same.
working on outbards wasnt my first choice in life.
had 2 kids and a wife when I was discharged with a montly check of 320 a month, but hey they are paying me 496 a month now .
wont go into the 47%.
but it takes a lot to be successful in this carreer.
luckily spelling and grammar are not at the top.
I also do mercruiser and volvo.

[Gert Geyser]

CatCam - Thanks for the eBay link I will have a look for the cowling, I did place an order for the CDI and Wire harness at boats.net, I just have requested to have my order changed so I can add the regulator / rectifier as well as the other parts have not been shipped yet.