89 Merc 150HP outboard Charging issues.

Alright guys hoping you can help a guy out here. Bought an 89 Ebtide 18ft. with a Merc 150 HP black max outboard. Boat was on consignment at the local dealer nice guys and they did their dues and had went through the motor before selling it so it was good. We took it out an ran it through its paces ran good and hit 47mph(GPS) with max capacity of 750 lbs in the boat.

So here i am two months later and i have a few problems. Biggest being the battery is not charging. Dealer put a fresh battery in before i bought it because it had been setting for 6 years in a garage. He drained everything and changed fuel and fluids just for piece of mind. It seemed a little cold blooded last weekend starting since it hadn't been started in a few weeks. Didn't pay no mind to that as i was told their cold blooded. Ran good for the most part but slightly different in sound. I am new to boating as an adult and operating one. I was however a Navy electrician and have been working on motors since high school but these outboards are a little different animals. Friday rolls around and i forgot to prime the fuel so it cranked over four times before i realized what the issue was. So i corrected that and it started cranking slow. battery was low. So I got a new deep cycle for the future trolling motor; jumped it off that battery. It started and ran fine. Went to the fishing spot shut it down, and few hours passed and went to leave the battery was dead. Granted we weren't underway a long time but i would have thought running a few miles up river would have charged the battery up a little. So swapped the batteries and the motor started fine with the fresh battery.

I am thinking its the voltage regulator or the stator. Called the boat dealer he was kind enough to tell me where to check with my meter to see if i am getting good voltage into the voltage regulator. He said on the two yellow wires coming off the stator i should get 180 to 200 volts peak. Is this at idle or at X value RPM? At idle at the ramp i was getting 7 VAC to phase to ground. Phase to phase 10 VAC. Is that normal or am I checking it wrong? I was also looking at prices and i see the Voltage regulator is 600 plus through the dealer and the stator was 500 pus. If there is something else i need to check i can do that too.

Any help would be awesome. Single dad just trying to take his son fishing safely.

Thanks in advance.

P.S. at 5500 RPM with just me in the boat i was only running 46 mph with calm water.

Another quick thing, does this hurt engine performance/efficiency?

You will only get 12-25VAC on the yellow wires from stator. You need to check the rectifier/s as you could have the big one on exhaust plate between the cylinders or the single ones..

the charging system has nothing to do with the running....you can use the rig safely without damaging anything...

i would charge the battery good with an external charger...it should read 12.7 volts or close to it when you remove the charger...then run the boat in neutral at 2k rpm's..after a couple minutes the reading should exceed the battery output...it dont matter at this point how much it exceeds it...if it exceeds it then you are charging...when you take the boat out and increase rpm's then it will go up...if it is a regulator it will be around 14.8 volts...if it is a rectifier only system it will go higher..

you can safely use the boat as it is if it starts right and dont need a lot of cranking to start it...the battery is just used to start the engine..after that it is not used in any way to run the engine...you can get many starts out of a good battery that is fully charged when you put the boat in the water..use a separate battery for the trolling motor...

do you have a tach in the boat and is it working?regulator or rectifier output is not a flatline dc as it is not filtered down all the way...the tach runs off these ripple pulses...if the tach is working your charging system is probably ok.. or at least putting out something...there is a possibility that the wiring has been altered to make the tach work with a bad regulator...the grey wire feeding the tach can be moved to one of the yellow wires coming from the stator and the tach will work off this signal..so if the tach is working and you do not see charging voltage you may want to check that...

be aware that as rpm increase so does the frequency of the stator output...this does not normally matter on most meters as they cover a good frequency range....but i personally would not rely on one of those 3 buck harbor freight ones..i carry a little yellow GE one sold at walmart for around 20 bucks as a boat tool box meter...

the charging system has nothing to do with the running...you can use the rig safely without damaging anything

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Not quite correct as if rectifier/battery is shorted/bad it can cause the stator to overheat and effect the high/low speed windings which in turn can cause missing/running and no spark situations and damage stator!!! Also you should have the water cooled rectifier/regulator and output can only really be tested with a load bank. Here is how to bench test it....http://www.outboardignition.com/support/194-1873.pdf

True...but i suspect that any damage would have already occurred..a shorted diode dont last long before its completely gone though...but you are right Pappy.. he does have this exposure plus a fire hazard while the short exists...