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Weak Flywheel Magnets result in No Spark?

J

jimturner44

New member
I have a 150 HP Johnson 1996 J150EXEDB. I get no spark on any of the 6 plugs. I replaced the stator with a new one. I did all the resistance tests in the shop manual on the Coils, plug cables, checked the rectifier diodes, cleaned all grounds, checked the neutral cut-out switch - all things that could cause no spark. then I check the A/C voltage coming out of the stator coils. All three stator coils read about 25% of their expected voltage. Example, I read 23 volts on from the charging coil and the manual say it should be 100 volts. What to you thinks it is. Could it be weak magnets in the fly wheel? The magnets are all in tact and firmly in place. Need some troubleshooting advice to pinpoint the issue.
 
Is the boat wiring harness disconnected from the motor ?? Try that and jump the solenoid to turn the motor over.
 
fdrgator said:
Weak flywheel magnets just do not happen since WWII days. Unless you run them through the smelter.
Click to expand...
Thanks very much - rule that out. I bought an OEM stator and will install it this week. I hope that solves it. - Yes, I have a remote key switch wired in. The engine cranks, just lower that expected voltage out of the power and charge coils.
 
Yes, I believe so. I put a new 800 CCA battery this weekend and took out the plugs to give the engine every chance to spin fast enough. the voltage readings on the power and charge coils did increases slightly due to the increased cranking RPMs, but were still about 40% below minimal required to effect the power pack and coils. so, I ordered a new stator and will try that route.
 
Boobie: OK - New information to troubleshoot:
I put in a new stator (OEM) for this 150 Ocean Pro. Same issue - low voltage on the power and charge coil -about 60% of needed voltage to cause the power pack to spark the coil. I counted the cranking RPMs with a slow motion camera - got between 41 and 42 revs for 10 Seconds - or 246 to 252 RPM. This seems a bit low. Obviously the faster the flywheel turns the more voltage induced on the stator.
Do you know if the 246 RPM to 252 RPM at cranking is fast enough?


This could be the issue if it is not the magnet strength. If so - how do I speed up the cranking speed?
 
Needs to be 300+rpm. Also don't worry about voltage on org charge wire as this does not produce 12+volts till engine starts, that why they get 12+volt from starter solenoid.
 
OK good to know - sounds like slow cranking RPMs. How do I correct that? I just put a new 800CCA battery on the test stand, I put a charger on the battery when I crank the engine to help give max voltage to the starter. all the connections are clean from the battery, to the solenoid and the bus bars to the starter. I have the plugs out to allow the engine to spin as fast as possible.
Follow me on my math: I am getting 60% voltage expected at 250 RPMs. I need the additional 40% speed to product the expected/minimum voltage out of the stator. 250 RPM X 1.4 = 350 RPM... Help me on how to get more cranking RPMs. I will double check there is no voltage drop to the starter, then what? Have you seen a started go bad or drag or loose speed. In a DC motor/starter, speed is a function of voltage. Let me know your thoughts. thanks for staying with me on this.
 
Yeah, it is supposed to crank around 300 RPM, but believe it or not, they'll start with a rope pull. Can't say I've ever rope started a V6, that I can remember, but have done it on V4's (many years and many tears ago). Where did those muscles go?
 
OK - Issue solved. Not weak flywheel magnets. Low cranking RPMs - not fast enough on cranking to induce enough flux to produce enough (minimum) voltage to the power pack. Remedy was to install an new starter motor, (installed a new solenoid as well). The new starter provided a faster cranking speed, enough to produce the voltage out of the stator to fire the power pack and ultimately the spark plugs. She fired up and ran strong on the hose. thanks for the help.
 
Had same thing happen on my 2007 Yamaha F115's after a boat overhaul: I had a brand new 800 CCA battery too, new starter motors, and NEITHER of my twins would fire. The mechanic didn't know what it was, but suggested putting a SECOND battery on. Bought a second 800 CCA battery for each motor, wired in a new 2-battery switch, and motors both started right up.

Why did they even start before? I had 1,200 CCA Cat "D" batteries before, one each motor; battery store on island was out of Cat D's, so I bought the biggest battery in another brand they had, without suspecting what would happen.

An old-timer on another forum tole me that the Yamaha ECM (Electronic Control Module) counts the rpm's, and won't send juice to the ignition coils AT ALL, unless the crankshaft hits a high enough rpm. Second battery produced the high-enough rpm, and she fired.

Thanks for your info, guys; I'm learning more than I ever wanted to know about fixing outboard motors. Now if Daddy had only been a banker...........
 
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