1987 Merc Black Max XR-2 Charging Question

[Rush]

I installed a Holley Blue fuel pump, regulator, fuel filter, water separator, water pressure gauge, temp sensor and temp gauge last month.

I just bought a brand new Marine cranking battery in December at NAPA. I went out to fire up my engine this weekend and the battery was dead. I just wanted to check out my fuel pressure, water pressure, idle speed, and temperature. I always keep my battery switch off, unless I am going to crank the engine.

I charged the battery for about 12 hours. I started my engine up fine and adjusted my fuel pressure to 4 psi. Everything was working and the engine was running great! After about 10 minutes of running, the engine died. When I tried to restart it, the battery was dead. The engine should be charging the battery during that time. No other power was being used, except for the fuel pump. It sounds to me like a bad battery ( dead cell )

What could be the problem?

How do I do a voltage output check on my Black Max XR-2? I want to check it anyway, just to ease my mind!

Just out of curiosity, What is a "ball park" figure, of how long a fuel pump will run, under a fuel load, on a new battery with the engine off?

[Capt.Insane-o]

well, at idle with a blue pump under regulated load your fighting a losing battle or just breaking even with charging. as far as the last question goes, The blue pump draws 3-5 amps depending on fuel flow. So, how ever long you reserve is in the battery.

[Eagle One]

The charging system on that engine is a 9 amp system I believe. At idle you're not making as much as the pump is drawing but even then a hot battery will hold up several times longer than your situation. Could be one or more of these: a bad battery, a bad rectifier(tach will quit if the rectifier is out) not charging, a voltage drain,could be through the trim pump or in the boat wiring itself. Hope this helps.
Eagle One

[MadTing]

Remove the positive and negative battery terminals from the battery, and check that the keyswitch is turned off. Connect an ohmmeter to the terminals. It should read zero (0) ohms. If it doesnt, you have a short somewhere that is running your battery down. If it is, get the battery replaced.

To check the output, attach a voltmeter across the battery terminals. It should be around 12 volts. Start the engine and increase the idle speed to no more than 3000rpm. The voltage should increase to about 12.5V. If it does not increase, you will need to check your rectifier/ regulator and/or stator.

[wideglide55]

If that "marine cranking" battery is a deep cycle battery,thats your problem.They will smoke your stator in short order.

[Rush]

It is a regular cranking battery.

I will try the voltage and ohms test. I would have thought that the battery is receiving more charging voltage, than just 12.5 at 2000-3000 rpms? I need to find a manual for this old motor.

How much charging voltage do most outboards get while running?

If I am running a Holley Blue fuel pump, which is sucking 4 amps, and I am only getting 12.5 volts while running, I am worried that this combination is not gonna work.

What do you think?

[transomstand]

Remember, voltage is the power available, or pressure, amps is the rate of flow. Two very different animals.
At 3000 rpm, the voltmeter should indicate about 13.5 to 14 volts. I'd have to question the battery, running a fuel pump 10 minutes should not kill it.
1st, charge the battery, let it sit 30 minutes, test with a load tester, if it passes, check for a draw. Disconnect the positive terminal from the battery, install an ammeter between the battery and positive cable. With everything off, you should have a zero reading. If it passes these tests, disconnect and test the rectifier. I'll look up the procedure if somebody doesn't already post it. Let us know what you find.

Pete

P.S. Go straight to a Merc dealer and order a service manual, best 35 bucks you'll ever spend.

[wideglide55]

Disconnect battery,diconnect all wires leading to rectifier,set ohmmeter to Rx1,000 scale,connect red ohmmeter lead to ground and black test lead alternately to terminals A and C,both should show continuity.Connect black test lead to ground and red test lead alternately to terminals A and C, meter should show no continuity .Connect black lead to terminal B and red lead alternately to terminals A and C the meter should show continuity.Connect red lead to terminal B and black lead alternately to terminals A and C,the meter should show no continuity. If any of these reading are not correct rectifier is bad. I would also test stator as you should be carrying more than 12.5 volts at 2ooo to 3000 rpm.

[pyro]

Remove the positive and negative battery terminals from the battery, and check that the keyswitch is turned off. Connect an ohmmeter to the terminals. It should read zero (0) ohms. If it doesnt, you have a short somewhere that is running your battery down. If it is, get the battery replaced.

To check the output, attach a voltmeter across the battery terminals. It should be around 12 volts. Start the engine and increase the idle speed to no more than 3000rpm. The voltage should increase to about 12.5V. If it does not increase, you will need to check your rectifier/ regulator and/or stator. What the hell? :confused:

zero ohms is a dead short. What kind of crack you smoking?
The meter should read OL, "infinity" or nothing at all. Over 500K would be an insignificant leaky current draw that wouldn't hurt anything.
On top of that, the ohm meter may read differently depending on which way it's connected.
The CORRECT way to check for key-off current draw is to connect a series ammeter (AMPS, CURRENT) inline with either the pos or neg side, and look for current draw from the battery.

I am sick to death of people with NO CLUE trying to help out. If you KNOW the answer, feel free to chime in. If you think you might know the answer, keep it to yourself and do some reading, educate yourself.

[MadTing]

Sorry. My mistake. I did not reread what I typed. Yes, it is supposed to be 'infinity' and not zero (0) ohms.

[Rush]

The main big black battery ground going from the battery to the ground on the starter, needed sanding and cleaning at the starter. After cleaning it really good, I tightened it back up and put some liquid tape on the nut and lockwasher. It works like a charm now.

It was just a simple bad ground all along, but since it was good and tight, I didn't spend too much time looking at it until yesterday. I am putting out around 13 volts at 2000 rmps, but I will do more testing when it gets warmer. It was just too cold and pouring rain to enjoy messing with over the past few days.

Thanks for your suggestions!!!!! ;)