Trojan Boat Forum

We've only had time to run our new 1977 25' Trojan about 6 hours, but have concerns that the alternator may not be functioning properly.

The volt meter never reads more than about 12.5 volts even with the engine running and drops down when any accesesories are turned on. We've never yet run the boat for more than 2 hours before being plugged back into shore power and battery charger turned back on.

The boat had three batteries in it which were wired parallel and all turned on. I am concerned that I may have been running off reserve power of the three batteries and simply recharging them each time rather than relying on the alternator.

Subsequently to the boat being winterized, I replaced the three batteries and replaced with 2 high capacity marine batteries and installed a switch on each battery so that each battery can be turned on individually and used one at a time. (One for starting the engine, one to use for lights, etc when anchored at nighit. I figured they were getting old.)

Just want to know what I should be looking for...how to check (test) the alternator next spring to make sure everything is charging properly. Is the voltage regulator separate from the alternator on this boat? If so, where is it located?

Thanks--you all have been so helpful to us new owners!!!

diet rite
while your engine is running, you should be reading approx 13+ volts without any major consumers running, like a heater or an air conditioning system,
I would check the alternator, some alternators have what they call an exciter wire going to the back of it, unless its a one wire system, if its a one wire sytem I would take out the alternator and have a shop test it
if it has more than one wire running to it check to see that it is grounded when the key is on,(not the battery wire) how I usually check it is with a test lamp connected to that lug on the back of the alternator and attach the other side to a good known positive source on the boat, when you start the engine, and rev up to about 2700 it should put the lamp out signifying the alternator is charging ,
as I mentioned you have at least 13 volts while running

also an easy way would be to put a volt meter on the battery when the engine is running and see what the voltage is. should be above 12.5vdc at least and should be more (if you dont have one they are very inexpensive ones. you will need one later for checking circuits, grounds, bulbs etc.) turn on some lights or something with a heavy dc draw and note what the voltage does. if your voltage stays up then its charging . you may just have a dash guage that isnt correct

Remove the alternator and take it to your auto parts store. Most auto parts stores can check to see if the alternator is working properly. This way you'll know where the problem is. From your description it sound as if the alternator is not charging the system. When the engine is running the output voltage should be 13.6 volts. I believe the output of the alternator is 35 amps.

once you get it fixed a great tool is to add a 3 bank volt meter.

http://www.westmarine.com/webapp/wcs/st ... assNum=694

this way you can check the condition of any of your three batteries any time while running, on the hook, before starting, while charging, at the dock, on the lift, etc.

One of themost valuable items I added to the boat.

RWS

On my chrysler engines the alternator has a oil pressure switch that activates the alternator when the engine is running. It allows the engine to start with less load on starter. If the switch is bad no charging, jump switch with engine running or test for continunity with engine running.

David,
What engine did you have with the oil pressure bipass switch? Was it with the F36?

Yes,F-36 The switch is located with the oil pressure sending unit. Mine has a manifold with both senders side by side on the top of engine above the transmision.

440 Chrysler

I got a 79 F36 with 440's. I also have an alternator that may not be charging. I'll look to see if I have the oil pressure cut out switch before I remove the alternator and have it checked.
Thanks,

Before this thread gets too far away from the original question....Dietrite, the answer to your original question is most likely YES - your alternator is cooked.... Been there three times since 1999 (you'd think I'd learn...) All three times were due to the single 1-2-All-Off battery switch either turned to OFF while underway (my bad 1 time) and the actual switch being faulty and disconnecting due to a bad contact while underway (switch bad 2 times). I had the alternator rebuilt (not replaced) and THEN (duh) replaced the faulty switch. Since then I have also installed an ACR (Blue Seas) Auto Charge Relay that monitors all batteries (2 house and one starting) and charges all banks as needed - either underway off the alternator or at dock on the charger. No need to worry about switching while at anchor as it automatically switches to house bank and never lets the starting battery run down. You don't want to be underway with no alternator. Hope that helps.

WOAH, Dietwrite, before you asume it's the altenator check the external voltage regulator if you've got Chyrslers. I've replaced them 3 to 1 over have any altenator repair. Rich

Good point on the regulator. I find that mine doesn't open up until I crank the engine above 2000 rpm after there's been a load on the batteries (at anchor or unplugged for more than 2-3 hours). Sometimes I'll slip it into neutral and goose the throttle to open the regulator. I'm sure the regulator would open over time, but I get impatient.