How does a '82 BM 150 Charging system work?

[aby n]

1982 Mercury BM 150hp sn# 6101202

So i have a 1982 BM, i recently put battery voltage on my lowrance screen & have noticed at idle / low rpm the system is putting out ~13.7v via lowrance. But at higher rpm it's 15.x V

I get that the flywheel with magnets is spinning around the stator, creating juice.

I'm unclear of the rectifiers job & how it's involved.

How does the electricity get funneled back to the battery? Which wires? How should it be routed back to the battery / what is the proper wiring route?

How does the electricity get regulated? Does it? Is the stator made to only produce a certain amounts of amps?

The cdi unit i installed is claimed to be a 9amp unit.

I tried watching a few utube vids, but my questions werent answered.

[leonreno]

What CDI component did you install? Stator? regulator?

the stator produces AC current which is rectified to dc current and the dc output is regulated by the regulator.

edit/ looked up your motor, doesn’t appear to have a regulator. So the output voltage is unregulated, which is probably because of it only being 9 amps. But someone who is more intimate with these systems will be able to answer more accurately.

[aby n]

Thanks leoreno, i installed a cdi stator.

I spoke with cdi earlier today & he said my duralast 31-950 was the issue. He said the maintenance free batteries are the issue.

He also said the deka batteries are what they use at cdi for the older stator motor testing & they accept the charge.

I will give them a call tomorrow to try & get a better list of batteries they tested, both good and bad.

sucks that i paid what i did for a battery that might not work for my motor, when it comes to receiving juice from the stator/rectifier.

I wonder if this is the reason the yellow wires fry themselves...

I ordered a 9amp stator, now i just need to inspect the tag to verify that is indeed what i installed.

[JOE54]

make sure tag does not say 5456-16, the -16 is a 16 amp

[CatFan]

Thanks leoreno, i installed a cdi stator.

I spoke with cdi earlier today & he said my duralast 31-950 was the issue. He said the maintenance free batteries are the issue.

He also said the deka batteries are what they use at cdi for the older stator motor testing & they accept the charge.

I will give them a call tomorrow to try & get a better list of batteries they tested, both good and bad.

sucks that i paid what i did for a battery that might not work for my motor, when it comes to receiving juice from the stator/rectifier.

I wonder if this is the reason the yellow wires fry themselves...

I ordered a 9amp stator, now i just need to inspect the tag to verify that is indeed what i installed.

What issue are you having? Sounds like your charging system is working like it is supposed to.

The battery isn’t causing any issues. Brand is irrelevant to operation, and even if it was, your Duralast is made by East Penn, just like Deka.

[JOE54]

say overcharging , would check bat voltage at batt while running with digital meter at batt terminals , analogs can lie

[aby n]

Thanks guys, i will verify.

[silverbullet02]

That's not uncommon to run high voltage with those systems.

[EuropeanAM]

Turn on some pumps or livewells. Pretty rare to see a boat in these forums that can't find a good use for 9 amps.

SOME of those engines had both a rectifier and a regulator. Some just a rectifier.

It is theoretically possible to retrofit a later-style regulator to that engine, but requires a good working knowledge of the circuits, connections, and regulator function (also note that it is NOT manufacturer supported, either).

You were told correctly about Maintenance Free batteries- you should be running something that is a flooded-wet cell (meaning you can remove caps and adjust the electrolyte level if needed).

[aby n]

I didnt realize that there was a difference between the 2 autozone duralast 31-950's, 1 being MF & a flooded wet cell.