Stator or Voltage Regulator? - 1989 Blackmax 150

[capecodguy]

This is my first post here so I will try to give complete information. I have a 1989 Mercury 150 Black Max Serial #OC126999. It has a 40A stator with a single voltage regulator. Over the last year or so, I have been having an intermittent problem with the oil warning horn going off when first starting. I replaced the tank cap, warning module and motion sensor to no avail. About 20% of the time it happens and almost always when the engine is cold. I am sure I am getting oil to the engine. I also have a intermittent problem with the tach dropping to zero either from idle or at throttle (warm or cold). This finally lead me to test the charging circuit. I don't have a voltage meter in the dash so all the results came from a multimeter. All the connections are clean of corrosion.<br /><br />Diagnostic results.<br />1. No tach, no charge to the battery.<br />2. Tach ok, charges at 14.4V (sometimes) but 16V or more(sometimes). Bad for my AGM battery!<br />3. Checked AC voltage from yellow leads on voltage regulator. 16 VAC as expected.<br />4. Checked DC amps from red lead (starter solenoid) to both yellow stator leads. One was zero (expected) and the second was -5A. I am not sure if I am supposed to be using AC amps (manual unclear).<br />5. Performed Stator Coil Ohms test. Read zero Ohms across yellow leads (supposed to be 0.05-0.19) and zero ohms each yellow lead to ground (expected).<br /><br />I did move the lubalert to a different switch box terminal today and I didn't get any extra warning beeps.<br /><br />So is it the voltage regulator or stator? I think these tests indicator stator but that means hauling the boat to a mechanic due to having to the pull the flywheel. I can change the voltage regulator myself on the water. Otherwise, the engine runs fine. The intermittent nature of the problem doesn't make sense to me. Wouldn't the stator just either work or not? And a about $500 each, I don't want to make the wrong guess! Thanks in advance for your assistance.

 

[capecodguy]

Re: Stator or Voltage Regulator? - 1989 Blackmax 150

Shameless Bump

 

[Laddies]

Re: Stator or Voltage Regulator? - 1989 Blackmax 150

First let me say I am no V6 expert, but I will try to help, I think that you be confusing some of them with some of your facts. According to my manuals the 150s did not come with a 40 amp system only the 175HP and up in 1989, all 40 amp systems used 2 regulators (has someone converted yours if so was it done properly?) Beyond that a bad regulator could causes your charging and tach problems. Ussally if the stator OHMs at at it will work, when the output volts surge it is ussally the reg., when the tack don't read it is ussally the reg. Hope this helps a little and might get someone else to help

 

[phatmanmike]

Re: Stator or Voltage Regulator? - 1989 Blackmax 150

i have a 1993 200hp merc v6 and my tach will sometimes not register at all below say 1500 rpms or so, and when it does this at idle, my batts arent getting charged.<br /><br />i have been told by others on this board to check the output of my voltage regulator/ rectifier. after hearing your problems, i think we just answered each others questions.<br /><br /><br />mike

 

[KCLOST]

Re: Stator or Voltage Regulator? - 1989 Blackmax 150

The intermittent oil alarm going off can indicate a bad switchbox... As your test proved...<br /><br />You can switch the lube alert lead to another terminal, but I would check for spark to ensure that you don't have a misfire condition on that cylinder (coming from the switchbox)...

 

[KCLOST]

Re: Stator or Voltage Regulator? - 1989 Blackmax 150

By the way, the Regulator(s) should have no affect on the oil alarm... <br /><br />If the stator was faulty, you would have no spark or a very weak spark on one bank (all three). You can test it by again checking spark intensity on all cylinders at idle and then switch the stator leads going to each box. Retest for spark intensity and see if a no spark or weak spark condition moves to the other bank..<br /><br />Let us know...

 

[capecodguy]

Re: Stator or Voltage Regulator? - 1989 Blackmax 150

I definitely have a single large regulator with a 40 Amp output as measured with clamp-on ammeter. It is possible my engine is a 1990 but I think my serial indicates 1989. It looks like a stock installation and there is a Merc voltage regulator like mine available for my serial number.<br /><br />A bad switchbox is a possiblity but I don't have enough time with the motor running to find if moving the lubealert fixed that problem. <br /><br />Since the engines runs smooth at idle and at full throttle, it appears that I am getting full spark at each cylinder. I will test for spark on that one cylinder but since it is intermittent, it might be hard to catch. <br /><br />Lastly, since indications are it is more likely the voltage regulator, I plan to swap one from my other engine to confirm.

 

[phatmanmike]

Re: Stator or Voltage Regulator? - 1989 Blackmax 150

well.....?

 

[lisfisher]

Re: Stator or Voltage Regulator? - 1989 Blackmax 150

I had a faulty regulator and it WILL make the alarm go off.Not sure about the oil alarm but it used to trigger my overheat alarm.