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Author Topic:   Apparent Electrical Problem with Onset After 20-Minutes Engine Run
powerstroke posted 03-02-2009 08:21 PM ET (US)   Profile for powerstroke   Send Email to powerstroke  
I cooked the power head on my C.C. last fall. Chrome cylendars, so I tossed the block. I ended up finding a complete unit,controls and all for a decent buck. Problem is that the previous owner said it would run great for about 20 minutes then she'd slow down to 2000 rpm. After having his tech install plugs, 2 switch boxes,serviced the carbs,timing,impeller and thermostats they took it back out on the lake, same problem. Next time he said they noticed bubbles coming from the lower part of the block.(around the carb/reed area). Anyways,I bought it. I just checked the leads from the stator and, red/white to blue/white have a resistance value of O.L. Question ! (finally) Is this the source of the power loss and if it is, where are these bubbles coming from. I haven't put it on the back of my boat yet (the river is frozen) but I'd like to get everything in order before I swap the power head over to my lower unit. Thanks, Trevor
jimh posted 03-02-2009 09:38 PM ET (US)     Profile for jimh  Send Email to jimh     
Electrical circuits which exhibit a malfunction after operating normally for approximately 20 minutes can generally be diagnosed as having a sensitivity to heat, as it is typical that after 20 minutes of operation the device temperature has risen above ambient to a level that represents its long term operating temperature. An electrical device associated with an engine is even more likely to be affected by temperature rise after 20-minutes of engine operation, as there is a very strong likelihood that the device temperature will rise considerably. Therefore, I suggest you approach your electrical diagnosis by looking for components which are sensitive to heat.

Resolution of problems related to the plumbing system on your motor are outside of the realm of our electrical discussion. You can seek advice on the leaks in your engine cooling system in the REPAIRS/MODS discussion.

To interpret the meaning of the indication "OL" on your test equipment, check with the owner's manual or operating instructions for your test equipment. As a very general case, "OL" often indicates that the reading obtained was outside the limits of the range of values expected.

If you get "OL" when making a resistance measurement, check to be sure that the resistance function has been set to auto-ranging. If not in auto-ranging, it is easy for the measured value to exceed or fall below the range of values expected for a certain resistance setting.

An indication of "OL" may mean the measured resistance was too high, that is, the circuit was open and the resistance was infinite.

To compare the values of resistance you measured with the normal values, consult the service manual for your motor. Any coil winding associated with the main stator winding of the battery charging alternator will be in the range of 10-ohms or less.

powerstroke posted 03-02-2009 09:52 PM ET (US)     Profile for powerstroke  Send Email to powerstroke     
Thanks, I'm a diesel technician and only getting "self aquainted " so far in the 2 stroke side of electronics. The meter I use is auto ranging and did see values in the normal range of 5.6 k ohms on my red to blue wire resistance check.I'm assuming that there is an open in my stator or something has gone straight to ground . It's not within spec. so I'll put a new one on then continue testing. I'll check out the other topic site you've directed me to . Thanks again!
NewportMe posted 03-06-2009 03:51 PM ET (US)     Profile for NewportMe  Send Email to NewportMe     

Go online and order a repair manual for your motor. With your mechanical knowledge it will pay for itself many times over. My manual has electrical troubleshooting diagrams and flow charts with resistance and voltage values shown.
hope this helps

powerstroke posted 03-06-2009 04:55 PM ET (US)     Profile for powerstroke  Send Email to powerstroke     
Thanks Bruce , I have a manual however, my serial number is not in it! Any suggestions? Trevor

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