1996 Mercury 150 Electrical Problem

Hello -

I have a 1996 Mercury 150. Recently, the engine stopped charging the cranking battery. Once I recharge, it works fine. When I remove the leads from the battery while the engine is running, it stalls. I know with car engines, that indicates the alternator is bad. Do Merc outboards have an alternator and if not, how do they charge the battery?? Thanks in advance for the help!

Jim

Re: 1996 Mercury 150 Electrical Problem

Jim, Removing the cables from the battery while the engine is running will destroy your voltage regulators. That is likely why they no longer function.

On that motor, AC is supplied by a stator under the flywheel to the twin 20A VRs. These convert the voltage to DC, and regulate the battery charging.

Re: 1996 Mercury 150 Electrical Problem

Chris - Thanks for the info!

Re: 1996 Mercury 150 Electrical Problem

If the rectifier/regulators were not bad before, they are now.

Bad rectifier/regulators on your ignition can and will disrupt the magnetic 'field' within the stator and cause erratic ignition problems, i.e., cause the motor to 'die' when you disconnected the battery cables.

Since there is NO RETURN on $$$$ electrical parts you should test each rectifier before spending $$$$$.

Remove the rectifier and test with an Ohm's meter. Test yellow to yellow, each yellow to red, each yellow and red to ground. Write down your findings.

Now reverse your meter leads and retest each wire combination again. Write down your findings again.

Compare your findings, you should have continuity ONE direction only on the first notes, reversed should be the opposite.

If ANY combinations have the same continuity then replace the rectifier.

Re: 1996 Mercury 150 Electrical Problem

Charlie, Will that test work on the dual voltage regulators he has? I do not think he can get to all of the connections of each diode, since they are integral to the VR.

Re: 1996 Mercury 150 Electrical Problem

That test is for standard rectifier, you will have resistance readings in the 45K area. Attached is the CDI sheet that gives bench test and amp output tests.
http://www.cdielectronics.com/InstallSheet/194-5279.pdf