Rodbolt

[Captron904]

Tried to send you an IM, but not working.
Taking boat back to mechanic tomorrow on the surge problem. I guess we will try replacing the spark plug boots and run with the vacume gauge.
Could a low battery or corrosion at one of the battery terminals cause this?
Put new fuel pumps, ran a new fuel line from tank to seperator, new plugs, carb floats adjusted, man running out of things to spend money on..haha
any more info would be awesome as always.

 

[rodbolt]

Re: Rodbolt

easiest way I know of is to NOT splatter gun the testing and follow a logical test sequence using the correct tools,30 plus years of dealing with macines doesnt hurt either.
test spark,test compression clear the fuel system is typically how it works.
the engine doesnt have to be started nor the hull in the water to do the engine vacum test if your dealing with an actual Yamaha dealership with an actual yamaha trained tech,if your not all bets are off.
the plug caps can be tested quickly and easily with a standard digital multimeter.
to test the surging issue,once your positive its not a fuel issue, simply attach the stevens CD-77,or equivilant ANALOG peak reading meter to each CDI output and run it,if the needle starts swinging while its surging go look at ign producing devices OR ign controlling devices.
if CDI output remains steady and its surging go find the fuel issue.
also check the CPS sensor at the problem RPM voltage swings.
that engine uses 2 pulser coils to fire 4 cylinders and the CPS fires the remaining 2.
loose the CPS and you dump 2 cylinders,loose a pulser coil and you may dump 4.
loose a charge coil and you dump all 6.
so careful testing coupled with a thourough understanding of how the system works and why is usually the quickest way to deal with issues.

 

[Captron904]

Re: Rodbolt

Thanks, I'll keep this info handy to compair what mechanic is doing.
What is the CPS?
I did pull and ohm out the plug boots last night...nothing over 5.15 ohms
raining today, but will post up what we find.
Thanks again Rodbolt!

 

[rodbolt]

Re: Rodbolt

CPS is crank position sensor, gives RPM and crank angle information to the ECU.

 

[Captron904]

Re: Rodbolt

Update, found crispy stator, new one on order. Will install and run Friday.
One of the transformer looking things on the stator was melted and black.
Could this cause both high and low speed misses?

 

[rodbolt]

Re: Rodbolt

possibly, what was the charge coil output voltages at the miss range?
one of the first things to test before the splatter gun approach
remember that stator has 3 y wound coils for battery charging and two 2 wire coils for ign system capacitor charging.
dunno which one is crispy.

 

[Captron904]

Re: Rodbolt

It was pretty much melted and burnt, so needs replaced regardless.
There are 2 bigger coils on the left side (9 o:clock position) the bottom of the 2 was toast. Are the charge coils ones with green wires?

 

[99yam40]

Re: Rodbolt

If you would have taken voltage readings it would have told you which one had a problem. That is why they give troubleshooting guides with steps in the manual

 

[rodbolt]

Re: Rodbolt

no
green leads are lighting coils,battery charging.
ign charge coil leads are blue,red,brown and black\red.

 

[Captron904]

Re: Rodbolt

99yam40, great advice, thanks!

 

[Captron904]

Re: Rodbolt

Installed new stator, no more miss, runs good. Thanks Rodbolt