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MERCURY 1979 50 HP POOR SPEED AT WOT suspect stator high end

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peter1965

Member
Hi guys i have had my outboard for the last 14 years and dad had it for 20 years before me, it has served us really well a truly great motor but recently i 've noticed a problem with it and would like your thoughts on what i should do next,
outboard has good compression 120 (+/-) 2, idles perfectly and great low speed but once i push the throttle past 3/4 way it does nothing more. i suspect that the stator may be a problem (HIGH END WINDING).
i have measured the resistance of the stator leads and the results are as follows
red/white to red= 63 ohms, blue/white to blue= 6600 ohms (i believe red/white to red should be around 145 ohms)can somebody in the know please confirm, its a sierra stator.
I decided to take some DVA readings I built a dva adapter and connected it to my multimeter these are my readings with outboard at idle and given some revs
red/white to red =121 volts, blue/white to blue= 301 volts. at the power pack feeding the coils all read @ 250 volts.
I have read that voltage of red/white to red should not be lower than blue/white to blue is this true and is 120 volts too high, spec states 20v +
 
I will take the boat on trailer to the water this morning and check the timing to see if it does advance to the correct high speed before i do anything else and check to see if I have good spark, the odd thing is that from the cdi specs supplied above (thankyou for those) it appears the stator resistance readings are in spec for an OEM stator. I am wondering if the sierra stator that I have is the equivalent to the OEM ?. Its funny because I have seen specs at other sites that state a completely different spec range for high end windings.
 
hi I think I have identified at least 1 problem, went to the ramp this morning its only a 2 minute drive with 3 ramps (so I am not interfering to much with other users) and I checked timing and it does advance correctly however I can only get 2500 rpm at max spark advance. Then I primed more fuel and the motor didnt like it it seemed to want to flood. At that time another boat was launching that had the same motor as mine possibly same year he allowed me to ohm test his stator red/white to red the result read 143 ohms. mine reads 63 ohms. Given this info I retested my stator red/white to red with the dva adapter. On start up i get @ 180 v then as I push throttle in gear, it gets to about 280 volts and then drops sporadically as the engine misses, from 280 to 250 up and down. From what I have read so far I dont think this should be happening. I tested the blue wires I get 300 volts consistently. One regret i have is that I did not disconnect the stator rectifier lead and check the high speed wind again. and although the rectifier is charging my battery I have tested the rectifier for continuity and it passes all suggested ohms specs. I am anticipating that my stator is shot I wish I could truly verify the ohms spec for red/white to red before I go out and buy a new one, the cdi 1/114-5772pdf attachement you sent me specifies 125-155 ohms for the OEM stator, yet the 174-5454k1.pdf specifies it at 60-150 ohms. Am I reading it incorrectly ?
 
I have ordered a new cdi stator 174-5454 due to arrive next week, Kim yes the attachments have worked I now realise that the specs are different for specific flywheel magnets, mine being bolted in flywheel magnets. Thanks for all the references and I will let you know how it all spans out.
 
Installed the new stator and got my power back. Run at wot for @ 10 minutes with no obvious issues. One thing that I noticed is that the water coming out of the tell tale varies in temperature from warm to hot. warm at mid speed hot at wot. I can bare to touch the stream but is uncomfortable. is this normal? (i haven't paid attention to this in the past) I have rebuilt the water pump not all that long ago. During the rebuild one of the paper gaskets (the one that the base of the pump with the large o ring passes through) didn't fit. I cut out another using good quality gasket paper and used that. I am just wondering if this has had an adverse effect.
 
I do flush after every use as the motor is mainly used in salt water, I will drop the leg and inspect the impeller as a precaution but I am wondering if what I am observing with the temperature variation is normal or does the temperature remain constant through out a wide rpm. The motor has no thermostat
 
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