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Great board Merc 150 charging help

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ezgoewin

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"What a great board, can't

"What a great board, can't believe I found it. I need help. I would normally use a mechanic but Katrina took out most shops and nearly all good mechanics. They are running six to eight weeks backlog so I would like to try fixing this myself. I have a 1998 Robalo 1920 with Mercury 150XL carb (same year) less than 100 hours on motor. Model # 1-150422UD serial 0G594613. Here is problem. Took boat out ran fine coming back in it took several attempts to get it to plane out but it eventually did. I suspected fuel so I bypassed main and used 6 gal tank. Boat ran perfect. I know it doesn't sound like a charging issue yet. After replacing fuel lines and filters I ran it and it ran perfect. Next trip same issue upon return so I replace primer bulb. Ran perfect on test. Last trip boat ran perfect on the way out but when I tried to change locations it wouldn't plane again. After it eventually planed (and ran perfectly) I returned to the dock and when I tried to start the motor the battery was completely dead. I recharged and it held charge. I now suspect the motor only runs poorly after heating up. I suspect stator? maybe regulator/rectifier? only failing after heating up? No, the tachometer is not erratic. I am no mechanic but I have decent tools a digital multi-meter and the shop manual (athough it is very confusing with so many different models covered). I searched the posts so I have a little understanding of the charging/electrical system and I downloaded the DVA movie and will watch it next. Anyone want to help a novice along the way? Where would you start? Any special tools I will need? Merc stator is part#398-96-10A19 so I think it is an integral 40 amp system.
Ron"
 
Did I mention novice? Do I te

Did I mention novice? Do I test the voltage on the battery by touching the test leads to the wires? Won't that just tell me the voltage in the battery? Or do I disconnect a wire and put the meter in series? Is it possible that I have only a pair of voltage regulators and no rectifier? There is no test procedure on the linked page for stator btw.
thanks
 
"Ron, your battery should read

"Ron, your battery should read no more than about 12.5 volts when the motor is "not running" - should jump up over 13 volts if the charging system is working properly.

So no, keep everything connected..."
 
"voltmeter to battery before s

"voltmeter to battery before starting=battery voltage, voltmeter to battery while at rpm above idle=engine operating voltage. If battery voltage and operating voltage are the same then charging system is not working. Stator test is located in the vidio section. If you cant find it let me know."
 
"Sorry, one more note - don&#3

"Sorry, one more note - don't ever run it with the battery disconnected - unless absolute emergency.

That will fry your rectifier for sure..."
 
"Lets see, alternator dies, ba

"Lets see, alternator dies, battery goes dead, engine runs poor. Check charging system

"
 
"Wow, lots of help and fast..t

"Wow, lots of help and fast..thanks. Turns out my motor has no rectifier, just a voltage regulator part#883072T. JB I can't find that video section you mentioned, search didn't turn up anything either. Graham thanks for the explanation on the battery test. If the engine is working properly when cold will I have to heat it up to test it?
I will post results from battery test and go from there. thanks again
Ron"
 
JB looked all over that video

JB looked all over that video section and still couldn't find that stator test. Do you know the name of the topic/thread it is under?
Ron
 
look down a couple post for 15

look down a couple post for 150 black max problems. Graham has a nice chart. I was thinking ignition trouble shooting vidio for stator
 
voltage at battery engine off

voltage at battery engine off 12.66
at battery engine running 14.16 both with motor cold
I am letting it run and will check it again in twenty minutes
Ron
 
after idling for twenty minute

after idling for twenty minutes
voltage engine off 13.33
voltage engine running 14.16
My problem only seemed to happen after a 10 mile or so run at 4000 rpm's. Should I run it ten miles then test it when it won't plane out? Or try a different test?
thanks
 
"okay, I have read more in the

"okay, I have read more in the manual and have a little better understanding of the system. This is a 40 amp stator with a 20 amp low speed winding and a 20 amp high speed winding. Each winding runs to it's own rectifier/regulator. I removed each set of two yellow leads from the stator to the regulators and tested for continuity and they showed .000. I also checked them for short to ground and they showed no continuity. My question is do I need to be at high speed to test the stator output on the high speed winding? Manual says it will work on one but only deliver half of the normal voltage. Is it possible it only breaks at high speed or when hot and at high speed? help!"
 
I would start looking for dirt

I would start looking for dirty conections or faulty battery. My knowlege of your system is zero. Perhaps someone else can help. Good work so far.
 
"Ron, you have it partly right

"Ron, you have it partly right. Your stator does have low and high speed windings, but those feed your two separate switch boxes.

Your stator has separate, but integral "charging coils" that feed your two regulators. If the regualators fail, you will normally get an "overcharge" - cooked battery.

An undercharge condition could be caused by bad charging coils. And although they are separate from the "ignition" part of the stator, if they are bad, the whole unit needs to be replaced. However, based on your problem, the fact that you notice the "no charge" after running above 4000rpms, that actually would not make much of a difference - the increase in rpms should only allow the charging stator coils to produce a higher amperage - they either work good or are defective (regardless of the rpms).

Anyhow, you can test the charging coils. It is best to test them both "cold" and "hot" - so before and after a run.

To test you simply remove the yellow leads going to the regulators (there is a short pair and a long pair - respectively).

You only need test the resistance with an ohm meter. First test between the 2 short ones, then the two long ones. You are looking for a reading between .25 - .45 ohms with the meter set to R X 1. If it appears as a "short" - no resistance, that is acceptable as well.

Then test between 1 of the leads and good ground on the engine (first the short lead to ground, then a long lead to ground - doesn't matter which yellow lead you use).

You should have "no continuity" at all (no connection) between the lead and ground.

If those test are good, then your charging coils are fine..."
 
"Graham,
Thanks for the info.

"Graham,
Thanks for the info. I have run the tests you suggest and the results are posted two messages above. I am waiting to get a chance to run it and test with it hot. I will post my results. If charging coils are good then where would I go next?
Ron"
 
"Ron, this is getting to be a

"Ron, this is getting to be a long post and I'm getting lost
Don't see if you have tested the regulators themself - as stated, if they go bad they "usually" overcharge - but not always the case. They are supposed to monitor the "state of the battery" and stop charging if they see it's "full" - so they could be shutting down because of "defect"..

If those are ok, I would be looking more for something that is draining the battery - bad connection somewhere in your assessories or open circuit to ground etc. The easiest way to check that would be disconnect the main assessory lead and only run with the charging system and the battery - if the battery still dies, then it's being sucked dry by something "else" on board...

Or check to make sure that the connection between the regulators and the solenoid are good.

Also, have you had your battery "load tested"? Most auto places can check that for you. It may be charging ok, but the battery may not be holding enough to crank the starter. I lived on the east coast for a number of years, and even just the salt in the air was very hard on batteries - often had to replace on a yearly basis..

After using it to start it can take up to an hour or more for the charging system to get it back up all the way (assuming all is working fine and the battery will hold it). If you have something drawing a whole lot, that could well be your problem...

However, do that "hot" test - sometimes a stator's output will degrade when warm/hot - usually a sign that's it's on it's way to total failure..."
 
"Ron, just though of one other

"Ron, just though of one other easy test you can try. Noted back that you state the tach is not erratic - and it won't always go erratic with a bad regulator (but it could).

Your tach is only fed by one of the regulators. Try a simple swap - unplug the gray lead and plug it in the other regulator before you take it out next.

If it goes snaky on you, then you will know for sure that the "other" regulator is bad - but again, it could be bad and the tach could function normally.

But hey, easy test to try...."
 
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