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Low alternator ouput at startup?

the coil gets +12 VDC from the key switch...your system has no resistance wire in the engine harness....

where was the key (position) when you did the resistance measurement on the purple lead?
 
The key switch was on and the engine was off. I will double check the coil wire voltage and the use the jumper and report back.
 
I went to test the coil voltage today and here is the results. Started the engine and brought it up to operating temp and the alt. showed charging. Put my meter on the coil and voltage showed. 13.5V or more at times. Shut engine off turned on blower and key switch to on. Voltage started at 12.8 and started decreasing rapidly. After around 30 sec. the voltage dropped to around 12.2 and I started the engine. Alt. gauge read below 12v. Meter confirmed low voltage at coil at around 11.8V. Turned on blower and voltage started dropping again. Voltage dropped to around 11.18 and then I increased the rpm by barely bumping the throttle and the voltage jumped up to around 13.8 again after the alt. started charging. I am beginning to think that my entire "purple wire" circuit is bad. That is what feed voltage to the dash and engine components correct? Is there anyway to bypass the existing wiring to see if that is where the problem is? I have already ran a jumper from battery positive to both sides of the key switch and there was no change. I have pulled all purple connections off of the gauges and cleaned them and pulled the cannon plug apart and cleaned it. Any better ideas on how to trace the problem?
 
W/all due respect...can you read a wiring schematic? See pgs. 9 + 13. http://www.marinemechanic.com/merc/wiring-EN_03.pdf

There is one junction in the engine wire harness on the purple wire circuit...the big black dot. See it between the alt. and coil and barrell plug pin 5? If the connector on the coil does not have two purple wires connected together then that is not the junction. Find the junction and take it apart. W/the purple wires disconnected at the alt. and coil and the barrel plug disconnected check the continuity between the alt. and the junction (wires separated) and the coil and junction and the barrell plug pin 5 and the junction. All 3 should have "0" ohms resistance. Replace the segment of wire that has resistance. Note: one of the pages shows a diagram of the barrell plug pins. Get back w/the findings.
 
Personaly I think he is over thinking and over worrying.

If the alt charges at 1000 + rpms after starting and then charges normally the rest of the time but shows low voltage with an accesory on (blower. lights, etc etc)

No big deal.

Charging is charging........

Mine has done this for the most part since 1995.........boat is an '87..........alt died the summer of 2011........thats 24 years out of one alt.......

Again charging is charging...........should not be idleing for long anyway............1000 -1200rpms.. is best when putting along.......

JMHO
 
Guyjg, No offense taken.....I started taking the wiring harness apart to find the junction before you posted and had printed off the wiring schematic from the Merc 14 manual. I stripped the harness back and then had a thought...scary I know. I disconnected the cannon plug and put a remote start rig in place (the setup Kghost recommended), that put battery voltage to the coil and removed the cannon plug/dash wiring. I then powered the blower circuit with a jumper from the trim cylinder battery wire. With the engine off and the blower running the battery voltage dropped very slowly starting at 12.4V and after a couple of min. it finally got down to 12.10V. I started the engine with the remote rig and with the blower running the volts were at 12.06 and stayed there until I barely touched the throttle and then battery volts jumped up to 13.6 and held at idle. I let the engine run for 10 min and then shut the engine off and left the blower running. After 11 min. the voltage dropped from 13.4 to 12.22 and started charging as soon as I hit the key. The next test I moved the remote rig coil wire to the #5 pin on the cannon plug (purple to engine). I turned the key on and had battery voltage at the coil. I let the blower run for and dropped the battery voltage down to 12.24V and started the engine. I measured the voltage at the coil and it showed 13.5V and finally settled at 13.95 or battery voltage. At this point I believe the large majority of my voltage drop issue is forward of the cannon plug. While the alt. takes a throttle bump once battery voltage drops below to begin charging there was no substantial voltage drop like when the cannon plug is connected and the engine is being supplied power via the dash. Any recommendations on the best way to test the dash harness to identify the problem? Guyjg do you agree with my test results that it appears as the the engine wiring harness is perfoming as it should?
 
While the alt. takes a throttle bump once battery voltage drops below to begin charging there was no substantial voltage drop like when the cannon plug is connected and the engine is being supplied power via the dash.
Click to expand...
The alt. issue still bothers me. Did you continue to wire harness search for the junction?

In a previous resistance test you had the key switch on...I was never taught to test resistance w/a voltage in the circuit. The ohmmeter battery provides the necessary volts/current for testing. I want you to rule out the purple wire circuit on the engine w/the the resistance tests I described...each segment of the circuit has to be isolated during the test. If the purple wire circuit resistance is "0" then there is something wrong in the alternator...you proved the alt. has a problem when you removed the barrell plug thereby isolating the engine electrical from the rest of the boat.
 
thanks for the reply guyjg. kghost, what is your opinion on my test results of the engine wiring harness? I am heading out now to check resistance on the purple wires in the harness.
 
Ok, here is the resistance test results for all four of the purple wires that are spliced together at the back of the cannon plug. For the test all the wires were disconnected from their connecting point (alt., coil,ign module, and timing module). Readings were taken on a 200ohm scale and the meter shows 0.8 when tested against itself

From the cannon plug to:

Alternator-4.3 after 0.8 for meter- 3.5 ohm
Knock module-2.2 after 0.8 for meter-0.4 ohm
Timing Module-2.4 after 0.8 for meter-0.6 ohm
Coil-2.2 after 0.8 for meter 0.4 ohm
 
I just tested my DVOM; zeroing (touch leads together) the meter = 0.3 ohms.
I ohmed a 5' length of 18 ga. wire = 0.3 ohms less the meter resistance = 0.0 ohms.
I ohmed a 5' length of 1 ga. wire = 0.3 ohms less the meter resistance = 0.0 ohms.

Based upon my tests compared to your tests it is my opinion that your wire is corroded internally. If it were my boat I would replace the purple wire on the engine.
 
Guyjg, I definately agree that there is resistance and that at a minimum the purple alternator wire needs replaced. I will probably replace all the purple engine wires. Could the high resistance in the alt. wire explain the delayed charge when the voltage is low? My concern is that I still don't think that the engine wire is the cause of the low voltage when the blower is running and the hard starting with low voltage.
 
Could the high resistance in the alt. wire explain the delayed charge when the voltage is low? [/QUOTE It is my thought the resistance is interfering w/the excitation voltage to the alternator...maybe I'm wrong. I had a 1987 Baretta that had wiring problems from corrosion. I gave in and replaced all of the boat wiring and half of the engine wiring to solve the problem. The blower acted the same as yours does. I replaced it w/a lower amperage high volume 4" blower. That solved that issue. It required a 4" air duct and new air exhaust plenum.

If you don't use tinned wire as a replacement be sure to at least tin the stripped ends of the new wire w/solder before connecting them. If you don't know how to tin the wire ends check youtube for soldering electrical wires. All you need is rosin core or solid solder, flux and a solder gun all of which are available at most hardware stores. Don't use acid core solder.
Click to expand...
 
Back in Post #30, you indicated the wire had > 7K ohms resistance...??

And you really do need a known good battery to test the alternator...

Finally, checking the high current carrying wires with an ohm meter isn't worth the effort...the ohm meter doesn't use enough current to show any issues with the wire...and alternators need current to start charging...once turned on, they will produce their own field current.
 
Thanks for the help everyone, Kim it not an efi engine. Here is the background and what I have done so far. I bought the boat with a seized engine due to water intrusion from the bilge plug being left in and the boat filling with water. I rebuilt the engine and immediately had what sounds like the engine "kicking back" against the starter. Checked the timing, starter, replaced the ignition components, and tried a good battery. I followed kghosts advice and used a remote starting rig and separated the engine from the dash and the problem was dramatically better. I sanded and cleaned every connection and wire terminal I could find in the dash and on the engine and the problem got better but never went away. This summer while using the boat I noticed that when the blower was turned on the voltage gauge would drop and then the starting issue would be back again. The engine would eventually start, idle low, and not charge until you bumped the throttle. If I left the blower off after running the engine and started the engine it would fire as soon as you touched the key and charge immediately. After yesterdays testing I believe that the high resistance in the purple Alt. wire is contributing to the delay in charging and needs to be replaced. The engine started immediately, blower draw was very minimal (13.4V to 12.2 after 11 min.) and battery voltage was maintained at the coil with the remote start rig connected and the dash disconnected. I reconnected everything back together and measured voltage at the purple wire on the key switch. It started out with 12.34V (battery voltage was 12.45), I turned on the blower and the voltage immediately started dropping and within 15 sec. it was down to 11.8V. When I started it the "kickback" was present and it struggled to start. When it started the with the blower running the voltage continued to slowly drop to around 11.56V and then I bumped the throttle and it jumped to 13.56 and stayed there. I am beginning to suspect the dash wiring after eliminating the "kickback" problem and dramatic voltage drop with the remote rig, the delayed charging still exists due to the high resistance in the purple wire, and then the "kickback" and voltage drop return once every was reconnected to the dash. I checked resistance across the key switch and every connection that involved a purple wire under the dash and there was very little resistance. I did find a 0.5v drop from the key switch to the back side of the instrument cluster connection. Sorry for the long post just trying to sort out this issue. Any help or ideas on where to check next is greatly appreciated
 
Maybe order a new harness from the big connector back to the dash..........start NEW!!

This is a very common issue with boats as they age.......the wires get moisture and become green and increase resistance......nature of the beast with boats.

If you used the boat every day like a car this would take much longer to occur.....the sitting around reaks havoc with wires and connections.....


Especially in the northern climates.....or salt water climates.


Have you inspected the large pin connector?

Spread all the pins (very little, just enough to have equal slot gap on each pin) use a small amount of dielectric grease on all the pins, assemble and use a hose clamp just tight enough to not allow the conector to be removed.

Also remember, the purple wire in the dash comes from the ignition switch and feeds all curcits..........start there......would not be the first time a key switch was the culprit........
 
Kimcrwbr1, I had the blower direct wired to the battery when I had the remote start rig in place and the battery voltage drop was minimal. I am confident that the blower itself is ok. Kghost, I have seperated the plug and cleaned everything and tightened the hose clamp. I measured the ohms across the key switch and it was zero, I think I am going to put a jumper from the battery to the purple wire at the key switch and start working it back toward the engine until I find the problem wires.
 
Remember battery voltage comes from the battery via a 10 guage wire thru the big connector to the key switch.
this is your dash and ignition power....

the key switch then transfers that power to the purple wire and the crank (yellow w/red stripe wire).
Any weakness in the purple or ignition on circut starts at the key switch!!!!!!!!! This includes the volt meter/guage in the dash.
there also may be a fused link or breaker in this circut. typically labeled "ignition". no every boat has this...but you may.

good luck
 
Thanks Kghost, I wondered what the flow of voltage was. I am planning on unplugging and removing the dash components and the key switch, and jumper in voltage starting at the incoming harness from the engine and working backwards see if I can locate the trouble circuit or group of circuits. I checked resistance between the dash plug and engine plug on the purple and red/purple wires as well as the the key switch and its breaker and all showed 0 to a max of 0.2 ohms resistance. But I am still going to bypass the individual harnesses and components and see what happens. Let me know if you have any other recommendations and I will report by sometime next week with my results. Thanks again to everyone for thier time and comments.
 
Just a follow up and quick question. I disconnected the cannon plug and the dash harness and jumpered from the battery to the key switch and from the purple output from the dash back to the cannon plug purple. Fired everything up and it worked like a champ. Voltage held even with the blower running and the engine fired off immediately without kickback and the alternator started charging immediately without a need to increase the rpms. I then reconnected the cannon plug and the dash harness and disconnected the red wire at the dash circuit breaker by the key switch. I then jumpered a wire from the battery to the same dash circuit breaker (eliminating the main battery feed to the dash). Again everything worked great! Voltage held with the blower running and the engine started without any issues. This time the alternator didn't charge until I barely bumped the throttle, but then voltage jumped right up and everything worked great. So after all that I am going to replace the red/purple wire from the cannon plug to the dash. My question is, Is this the same wire that the alternator uses to sense when to start charging of does it sense off the voltage in the purple wire circuit? Again, thanks for everyones patience and help!!
 
kghost said:
Maybe order a new harness from the big connector back to the dash..........start NEW!! QUOTE]



As I suggested before........running a seperate wire leaves your boat in a state that ONLY you know what the wire is for and if someone else ever has to troubleshoot it may be at a loss.........................
Click to expand...
 
More than likely the pin/socket at the connector is oxidized or poor contact.

Not uncommon.


Like I said I have a few gremlins with my electrical but i will be damned if I am going to rewire the boat. Myvolt meter does work, it sometimes shows a condition like yours, a quick rev and all is good. Done much connection clean up over the years..My horn would only work when running.......took me 4 years to finally look only to find a small harness connector (installed by boat manufacturer not a merc part) had a weak connection......I tried all kinds of things including nice new dual automotive (loud) horns......this year I found it......now it works great all the time.

In the end, My in floor cooler keeps my beer very cold, My motor/engine runs very well, my outdrive goes up and down. So does my drinking arm.

My stereo is very loud and I constantly blow speakers.......All is good!!!

So some things dont seem to work perfectly, enough cold ones and i get past it...........

Such is life.....................
 
Thanks for the help Kghost! I am going to deal with the red/purple wire and then let it go. I have spent alot of time chaeing wires. I am going t adopt your attitude of dont sweat the small stuff and just enjoy the boat!! Thanks again!
 
Look at it this way,

It is your boat, the only boat you need to fix. Most who have tried to answer your questions have fixed many a boat and some more than many!!

Like many auto mechanics who fix others all day long do not typically want to fix there own so we sometimes take a different view on the small stuff.


Look what you have learned so far.........understanding the electrical system is a good thing for a boat owner.......


Wait t'ill you get into the mechanics of the transom assembly, gimbal housing (boots and bellows and shifting) and the outdrive.........

expect some grey hair..........haha
 
Haha, I have already had the thrill of pulling and rebuilding the engine and carb. Then was lucky enough to have to replace the steering cable and helm assembly that required fabricating a whole new dash mount. Last winter I had to rebuild the rear bench and sunpad including carpeting and sewing all new vinyl. I serviced the drive and noticed some corrosion around the shift cable so I am looking forward to replacing that in the spring...at this point rebuilding the drive is about all that is left. Someday I will just be able to launch it and enjoy it.....
 
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