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Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10621
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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1989 150hp mariner serial OC183687 the battery meter on the

Customer Question

1989 150hp mariner serial OC183687
the battery meter on the dash usually reads 14+ volts while running...it is intermittently not reading more than 12+volts lately...Tach is working, engine runs perfectly....suspect a bad battery (2 battery system), but can the regulator be checked by meter??? its the water cooled one and quite expensive to replace.....
Submitted: 4 months ago.
Category: Boat
Expert:  Tan replied 4 months ago.

Hello Joe. My name is Tan.

Have you tested the battery voltage before starting the engine then after you have started the engine and run it to 1500 rpms? Have you load tested the batteries?

The only test is an ohm test of the stator and charging out put.

Customer: replied 4 months ago.
Where is the charging output from the regulator measured ?
Expert:  Tan replied 4 months ago.

At the battery. The regulator connects to the start solenoid where the battery cables connects. So you test at the battery. Both before running and when running at 1500 rpms.

Customer: replied 4 months ago.
I assume that's where the dash VM is connected as well....
Expert:  Tan replied 4 months ago.

The dash meter gets it voltage from the purple of the key switch. The key switch voltage comes from the start solenoid where the battery cable connects at the start solenoid.

Customer: replied 4 months ago.
OK so I know one battery is bad...will change and see if dash meter reads 14+v when running 1500rpm
Expert:  Tan replied 4 months ago.

A bad battery will certainly cause a charge issue.

Customer: replied 4 months ago.
Thanks keep you posted
Expert:  Tan replied 4 months ago.

Ok.

Just disconnect the bad battery and run engine. Does the voltage at the good battery read higher with engine running than with not running?

Customer: replied 4 months ago.
No change... Reads the same....
Expert:  Tan replied 4 months ago.

What does the voltage read before starting the engine then when engine is running at 1500 rpms?

Customer: replied 4 months ago.
12+
Expert:  Tan replied 4 months ago.

Ok we haver a bad voltage regulator or stator. I suspect the reg as the tach still works. The tach works off the stator.

We need to test the resistance for the stator. Disconnect the 2 yellow wires coming from the stator check with an ohm metyer between the 2 yellows. What is you reading and check for short to ground on each yellow wire. What are your readings?

Customer: replied 4 months ago.
Tach comes out of the regulator....grey wire
Expert:  Tan replied 4 months ago.

Did you do the tests I ask? Are you concerned with the tach or the charging system?

Customer: replied 4 months ago.
Checked the stator when it started happening. Before you where involved ....stator good
Expert:  Tan replied 4 months ago.

Then I guess I don't under stand what the problem is? If the stator is good and it doesn't charge replace the regulator. This is very simple. So what is your concern?

Customer: replied 4 months ago.
Wanted to make sure before I spend $400....it has been intermittent
Expert:  Tan replied 4 months ago.

Have you tested the stator when it was hot and the engine wasn't showing charge?

Customer: replied 4 months ago.
Tested with engine in neutral ..... idling at 1000rpm...out of water with muffs on .....thermostats opened had hot water out of the tell hole...
Customer: replied 4 months ago.
If stator was ad wouldn't there be run issues
Expert:  Tan replied 4 months ago.

No the stator does 2 things it has coils for the ignition circuit and a different set of coils for the charging circuit. Although they are all in the stator they are separate systems.

Expert:  Tan replied 4 months ago.

Joe there is a test we can perform on the regulator. It doesn't always tell us correctly but we can try it. With your ohm meter connect the red test lead to the red wire and the black wire to the yellow wire note the reading then reverse the leads note the reading. The meter should read one way and not the other. Then test the red and the yellows to ground. You should have no reading.

Customer: replied 4 months ago.
Ok. Will try it
Expert:  Tan replied 4 months ago.

This may tell us or maynot. Ohm readings aren't always accurate. They can read good and the component can still be bad. The times ohm tests works are when they fail the test.

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