Can a faulty voltage regulator cause intermittant drop outs?

[richw46]

This is for a 1995 Mercury 2-stroke 115 HP. The OEM regulator was failing maybe 8 or 9 years ago and was replaced by a Mercury mechanic at that time. Voltage reading is up to 14 volts but normally around 13.8 when charging. Starting in fall last year I experienced a "bump" when up on plane at 40 mph. It happened from time to time then stopped. Yesterday I fished all day without a problem and just before reaching the ramp it really started happening again. It can happen if I throttle up or down, trim up or down, but not always. It happened when I tried to get the boat on the trailer and I had to crank it up by hand.

There is one odd thing that happens when I get this bump. The alarm beeps one time, only briefly. It will beep and I get the bump at the same time. The low oil alarm is disconnected because of a separate issue (I know what that problem is) so it could be only the overheating alarm, but the bump sometimes occurs when I first leave the launch ramp. There is a good stream of water coming out so I know it's getting water. I can continue at lower speeds and no alarm is sounding, so it can't be overheating. It has not happened at idle.

The only thing I can think of is the voltage regulator is shorting or failing. The wires look fine, no burning, although one wire was burned from problems with the OEM regulator putting out up to 18 volts 8 years ago. I replaced that connector and it looks OK. Is there any wire I can disconnect and run the motor to see if the problem recurs? Mercury has added an inline fuse to the sensor wire which mine doesn't have. The Mercury replacement kit is $208 but there are some regulators (Chinese I'm sure) that are only $29. I could get one of those to see if the problem goes away, then replace with OEM. Should I do that or is there something else that could be wrong?

 

[Chris1956]

You might look at a wiring diagram, but the VR is not usually connected to the ign system. The ign system will be ADI-style, where the stator charges the switchbox, and the trigger fires the switchbox into the coils. The charging system and battery are not part of the ignition system.

I would check the stator to switchbox wiring and the trigger to switchbox wiring.

 

[richw46]

Thanks for your reply. Looking at the connections on the switchbox I don't see anything unusual. While I have some experience in automotive repairs I've not done much with outboards. Wires from the stator and trigger come down from the bottom, surrounded by black plastic tubing and go down to the switchbox. When I pull the flywheel what would I be looking for, burned / broken wires? Is it possible the switchbox itself is bad?

 

[Chris1956]

The stator does have a coil that feeds the VR. It is separate from the stator coils that feed the ign system.

I am not an Electrical Engineer, but I suppose two coils sharing an iron core could have some influence on one another. I would therefore disconnect the VR from the stator, and retest the motor.

If she still cuts out, that would eliminate the VR as the troublemaker. Damage to the stator or the flywheel magnets should be obvious.

You might find a test for the stator and switchbox on the CDI Electronics web site, They sell all the ign parts aftermarket.

 

[richw46]

Thanks, Chris. I've ordered a service manual for this motor. I have found several sites that offer tests for the stator, trigger and switchbox. All of them are resistance tests. I don't know if there are any other kind. With an intermittent problem it's going to be difficult to find the issue with just resistance testing because it's not happening at low speeds. I'm considering just buying cheap parts to throw at it to see if the problem goes away.

Something I forgot to mention is when I tilt/trim the motor the tach needle will jump, not always, but if there is a beep from the alarm the tach will jump up a few points, or the alarm won't beep but the tach needle will jump when trimming anyway. Other times the tach behaves normally when using the trim. Oddball electrical issues are possible when something is failing. Voltage can be going anywhere, like to the alarm, even if that's not the problem. My trim/tilt gauge would bounce like crazy for a season. I thought the gauge or sending unit was bad. Turned out to be a bad ground strap between the lower unit motor mount and the swivel bracket where the sending unit is. I cleaned it up and problem was resolved

The CDI site sells a testing book but doesn't offer any free assistance. If the service manual doesn't offer any help I think I'm going with cheap parts. :-(

 

[Chris1956]

The tach jumping and the alarm beep could well be electrical supply or ground issues. Like that ground strap issue you found, the tach will jump if the ground or +12VDC is interrupted. The alarm beep can be the same thing.

Sounds like dirty wiring to me.

 

[richw46]

:grumpy: Yeah, have I mentioned that I hate wiring problems? Boat is stored indoors in a heated garage. Nothing jumps out at me as being corroded. I replaced the entire wiring harness several years ago. I replaced all the power trim O-rings because of this issue, thinking the small leak might be low fluid and causing the piston to have low pressure. The very first time this happened I was traveling at 40 mph, had just crossed a series of wakes from a passing boat, and I got the bump and beep at the same time. It was then I noticed the tach would go up (not a 'jump' but just a movement) when I trimmed. I haven't ruled out a pinched wire or poor contact. I have thought that maybe it's in the shift-throttle control. I know that's mechanical but the kill switch is in there. Maybe that's going bad. It doesn't address the tach movement or the beep but they're in that wiring harness. I'll take a look in there and see if anything looks out of whack.

 

[richw46]

Checked trigger wiring
Purple to White 847 ohms (800-1400 normal)
Black to Black 830 ohms (I don't know the normal)

Checked stator wiring
Red to Red-white 93 ohms (800-1000 normal)
Blue to blue-white OPEN (should be around 65 ohms)
Yellow to Yellow 1.3 ohms

Battery was disconnected during the readings. Readings were taken while wires were off the switch box and not being touched by me. I checked the blue wires several times but it was always an open circuit. I know open is not normal but I'm experiencing an intermittent problem, not continuous.

Does this mean the stator is bad??? If so, would the motor still run like it does?

 

[Wayne2]

I would like to wire a a security access alarm on my 215 pleasure boat. Would any one have a simple 12 volt alarm system wireing diagram i could have thanks.

 

[GA_Boater]

I would like to wire a a security access alarm on my 215 pleasure boat. Would any one have a simple 12 volt alarm system wireing diagram i could have thanks.

Wayne - You aren't even in the same ballpark with this post. Start a new thread of your own.

 

[richw46]

Back on track for my problem....
Came across something interesting on a different forum. A guy had a 2005 Mercury 115 2-stroke. He said he replaced the stator, rectifier and trigger and still has misfire at high RPMs. He disconnected the reverse RPM limiter and the problem went away. He reconnected it and the problem returned. The kill switch wire runs from the switch to the post on the switch box, then another wire runs from there to the RPM limiter. My DVM shows that wire as being ground. So maybe the RPM limiter is grounded??? Bad??? The part is $67 on Amazon so that may be a good place to start if I'm going to throw parts, especially since he has replaced 3 of the 4 other major electronic components without a solution and he never posted a follow up on the forum.

If that works for me, I'll post the solution here.

 

[richw46]

I posted reverse RPM limiter but it's the rev limiter. Anyway, I took that wire off, disabling the kill switch, and went fishing. I drove around a lot, over 40 mph. There were no drop outs, beeping or strange jumps on the tachometer. It seems this may be the problem, a faulty rev limiter. I've ordered the part and will replace it. If I don't post back it's because that took care of the problem.