Battery overcharging ?????

[Aquamaniac]

Cranked my old Merc 150HP V6 this AM to go fish. Sat there at dock listening to it idle nicely (finally..and after much work, I might add!)
Out of the blue ..... the Uniden radio alarms and shows "Battery High"
Indeed, voltage gauge read 18.
Shut her down, sat a minute, then cranked her up. Voltage gauge read about 13 for 5-10 sec, then climbed to 18 and alarm sounded again.
No where in Service Manual do I seem to find any help on OVER charging.....just undercharging.

ANY help would be greatly appreciated. Getting pretty frustrated trying to stand by this old beast....especially when I thought I had her right and now this!

[fitz73222]

Bad voltage regulator

[Aquamaniac]

Hey Farley,
Well, that was my first thought.....I just don't see any voltage regulator in the wiring diagram! ????
I did check the stator per Manual.....yellow to yellow> continuity. yellow to ground>no coninuity.

So where is regulator on this old beast?

[Aquamaniac]

Also....need to correct some info in first post.....
Voltage gauge is 10-16, not 18 (old gauge and hard to read, but old eyes don't help!)

Cranked her up after checking stator and reattaching wires.

This time it seemed to hold in 13 range for a while then slowly started to creep up. Turned on cockpit and panel lights and could observe slight drop in gauge. The gauge seemed to settle out at 14 at idle, would increase with higher RPMs, but not to 16 and no alarm. This is with the lights and radio on.

Wonder if the onboard charger is a factor? Although, with ignition on, not running, I get 13.54V at motor....so seems good. (?)

[Capt. Bob]

Is your (or have you noticed) tach acting "weird"?

It appears the VR is located close to the starter solenoid on an 84 150.

On my Yamaha, the VR dumps excess voltage to ground. It has a "range" (build tolerance) that can be fairly liberal (approaching 15V in its old age).
My experience has been that as they begin to fail, they give a few warnings (like the tach funnies and voltage spikes). Again, I've not owned a Merc but I'm thinking the theory is the same.

Good luck.

[Aquamaniac]

Hey CB,
No tach issues.
What is throwing me is that I do not see any VR in diagram....(??) Any idea what it might look like?

[Aquamaniac]

Here is pic of area of solenoid. The blue cylinder is suspicious.....and is connected to ground.

[Capt. Bob]

Well I'm backing out of this because it appears knowing serial #s is the best approach to what you have. I just was looking at 1984 150s. I looked at yet another site catalog and I see that some have 2VRs that are located by the ignition coils. Do you have the serial # or is it a mix of several years?

[fitz73222]

The blue cylinder is a Mercury switch (liquid mercury that is) that shuts the engine off is it is tilted to high while running or if an obstruction is hit at high speed. The other is a rectifier which only converts AC stator voltage to DC for charging the battery but it does not regulate output voltage. What AMP stator do you have? If it is 9 AMP there will not be a voltage regulator, if it is 16 AMP there will be a regulator. Check the voltage at the battery and verify the output voltage before you do anything else. Check it with DVOM for accuracy.

[Aquamaniac]

Farley,
Voltage on starting battery with everything off is 13.23
With engine started on that battery and running at idle, voltage is 14.03    Observed no spikes.
Shut down engine...voltage immediately 13.64 and slowly drifting down.

Don't know whether stator is 9 or 16...any way to easily identify??

Serial 6474916

[Capt. Bob]

Don't know whether stator is 9 or 16...any way to easily identify??
Serial 6474916

Using that serial # at the Mercury website and a second Mercury parts site indicates you have a 2.4L V-200 ELPTO.

As Farley stated you need to know the stator output. According to both part site catalogs this is accomplished by measuring the thickness of the stator laminate. Thickness of 1/2" and 5/8" indicate a 15 amp stator and require the VR. There is no thickness dimension indicated for the 9amp "stator assembly".

This is all very interesting.

Good luck.

[Aquamaniac]

CB:
Welcome to the confusion of Mercury serial numbers.
From what I have determined..... this motor is a 150HP V6 made in 1984.
V-150   6   6443213   1984
V-150   6   6616991   1985

Now to figure how to check stator laminate thickness....without disassembling that is!

[Capt. Bob]

I'd say you may need to pull the flywheel or...

If you have VR(s) you may find them (it appears two are needed) behind this plate.


Again, good luck.

[Aquamaniac]

Thanks CB. That plate looks familiar ;) ......guess I will try to get a peek behind it.
I have been doing a lot of reading.....
seems the 9 amp was used on Mercs of all sizes....and indeed had no regulator. Apparently one can replace the stator with a 16 amp stator from CDI/Rapair and retrofit a rect/reg. combo.
If stator is changed, would this affect trigger, switches, etc? That could get real painful!

What I have not been able to sort out is can one add a VR or rectifier/VR combo to a 9 amp stator? (assuming that is what is there)

For that matter, I still am unclear as to WHY the presumably 9amp stator is over charging.
I did find some things to try to check in AM:
- that your connections at the battery are not tight
- The battery is on its way out the door.
- Loose connections at the rectifier
- The resistance in the stator charging coils can change over time resulting in an overcharge.

Anything else? I sure hate to start throwing money at this and just replacing parts.
But something is definitely not right. I took boat out this afternoon after playing with it at the dock offf and on all AM. It seemed to have settled down and was reading 13-14 V at idle.....so I figured I would chance it.
Acted fine until really opened up throttle and pretty quickly went to 16V although no alarm sounded . Eased off throttle, turned on cockpit and panel lights......went back to 13-14....and stayed there for return trip.

Should note: the motor is starting, idling and running well

The good news?????? Tossed anchor before all the way home and caught some fish!!! Just to remind myself THAT is what I am "supposed" to be doing with this boat....NOT fixing it all the time!!!

[fitz73222]

If you decide to upgrade the stator to a CDI unit it will have no effect on the trigger or switchboxes, they are a separate set of charge coils that are in the stator windings and have nothing to do with charging the battery. Do you have the correct flywheel puller? You need the one that screws into the flywheel with the 1 1/2" thread. Make sure you note the correct orientation of the stator so that the wires exit the stator the same way as the old one. When you remove the allen head stator screws make sure you remove the old locktite from them and also clean out the holes they screw into. Brake cleaner will melt the old locktite. Make sure you clean the mounting pad that the stator sits on so the new one sits flat on the block. Put a couple of drops of 271 blue Locktite on the screws and torque them to 60 INCH pounds, the screws are long and small diameter and can be broken if over tightened. Clean the trigger friction points with simple green or some other mild detergent. DO NOT USE Acetone or brake cleaner to clean the trigger! Then put a very light coat of grease so the trigger rotates smoothly, don't be alarmed if the trigger seems loose, its the way they are. Also make sure the flywheel and crankshaft tapers are clean. DO NOT put oil or grease on the tapers, assemble dry. Any oil or grease on the taper will affect the torque value by creating and hydraulic action that won't let the tapers seat correctly and the flywheel could actually loosen later with obvious catastrophic issues. Torque to 120 foot #'s , but double check the manual for the correct torque. (i'm doing this from memory)