Is my alternator working

[Juzo]

had an unfotunate incident on the weekend, where I got out to Mud had a fish, went to move, and the motor wouldn't start, sound like there was not enough charge getting to the motor to turn it over. Luckily I could pull start it and off we went. IWas a bit suss on one of the connections, and was a bit slack with the battery set up. So off to bias, got some new cable, conenctors, and one of those battery box's with a little charge meter on to tell the state off the battery. plugged it all in and turns out the battery was flat, thought this was a bit strange as it's only 6 months old and I was out the week before with no probs. Have an isolator switch to turn it all off when not using.

Took the battery back to the cheap auto store, and they informed me the cranking amps were down to about 290 (from 500), and they kindly replaced it for me under warranty.

Is all ok again now, but what I want to know is if the alternator is working or not? Anyone know how to check this? figured I'd take the boat for a burn up the river, see if it charges the batt, but would like to check it out properly. I have a multi-meter, and some idea on how to use it

[Roughasguts]

Easy stick your multi meter on the battery with out running the motor
should read 12.6 to 13.2 volts.

When the motor is running and charging remember you have a new battery.

So do it right after start up the multi meter should read over 14 volts 15.5 is to much though.

[Juzo]

too easy, thanks mate

[Spaniard_King]

You wont get 14 volts out of it just after start up unless it's a 4 stroke.

Take note of the voltage before starting.. then start the engine and observe the voltage.. it should be more than the voltage when the engine is stopped.. now give the engine a rev and the volts should rise.. if you get no rise then you have a problem

Garry

[StevenM]

What Garry said Juzo

[Juzo]

righto, thanks guys, I stuck the multi-meter on it this afo, got 12.33 volts at rest. started the motor, voltage was about the same, but I'll try again tomorrow and give the motor a rev, see how we go....

[Roughasguts]

juzo you got a brand new battery so it might not show a charge, cause it don't need it.

Maybe run some lights off your battery for a while drain it a bit,
So it takes a charge just after start up. Or run some lights with the motor running, Hopfully you will see a change in voltage then.

[whykickacatalong]

If there is no charging going back in you will need to take it to a boat shop or auto sparky to test where it is losing charge. They will be able to isolate if the alternator is putting out the charge and if it is being stopped elsewhere such as the regulator/rectifier. Check if all your gauges (if you have some) are working such as the tacho. If these are dropping out it points to something else than the alternator (motor brand dependant)

[Juzo]

allrighty, I'll try these things out this afo, see how I go

[Juzo]

ok, second test, put the running lights on, got a reading of 12.18volts, started it up, 12.18/12.19v,

gave it some rev's and it climed to 12.26volts, so I read that as the alternator is working, and my prob was probably a dodgy lead (have fixed em up) and/or a faulty battery.

Will take it for a burn up the river on the weekend and see what volts come through when I can open the the throttle up.

thanks for all the advice

[Spaniard_King]

Juzo,

IMO you have a problem with the charging unit as when you rev the engine the charging volts should have risen to at least 12.5

12.26 is just the battery recovering a little after the start

Garry

[timddo]

thmm. all you gotta do is disconnect the battery when the motor is on. If the motor turns off the alternater is faulty. If it doesn't then the battery is.

another was is turn your motor on. disconnect the batter, but connect the cables together.. as in.. power your electricals directly from the battery.

if you have light. your alternator works.

simple easier..

[Juzo]

thanks Spaniard_King, I didn't rev the engine a lot, but I did watch the volts go up and down as I raised and lowered the revs.

timddo, I'll try your suggestions out

cheers

[Spaniard_King]

thmm. all you gotta do is disconnect the battery when the motor is on. If the motor turns off the alternater is faulty. If it doesn't then the battery is.

another was is turn your motor on. disconnect the batter, but connect the cables together.. as in.. power your electricals directly from the battery.

if you have light. your alternator works.

simple easier..

On what theory do you base these statements. Outboard motors espeacially 2 strokes do not require a battery to keep going

Hope you dont try running electronics with out a battery you will be loooking for new ones prety soon. Alternators are car type chargers. Outboards have flywheels,charge coils and rectifyers

I stand by my statements as per the above posts

Garry

[DaveSue_Fishos_Two]

Years ago I started an old ute that I had and while it was running I removed the battery. I can't remember why. I remember backing it out of the driveway though, and then a mate pulled up and told me that I had probably burnt out the diads? in the alternator from running the engine without the battery. Yep, sure enough he was right.

Dave