PDA

View Full Version : Alt issue


bareinnj
07-25-2010, 08:38 PM
2004 tt197. Last few sessions, the volts when starting and running are below 12, unless I put trans in nuetral and rev the motor, then volts jump to 14 or so and stay there until I turn off motor. Start it again, and volts are low until I rev it. Belt is good and tight, battery charges so long as I get volts up by revving in nuetral. Any ideas. thanks

thatsmrmastercraft
07-25-2010, 08:42 PM
Bad connection, slipping belt....................long shot - one diode out.

TX.X-30 fan
07-25-2010, 08:43 PM
Battery????

TX.X-30 fan
07-25-2010, 08:45 PM
If the battery will not take the charge then the meter will read like that. How big a stereo are you running?

JimN
07-25-2010, 08:51 PM
2004 tt197. Last few sessions, the volts when starting and running are below 12, unless I put trans in nuetral and rev the motor, then volts jump to 14 or so and stay there until I turn off motor. Start it again, and volts are low until I rev it. Belt is good and tight, battery charges so long as I get volts up by revving in nuetral. Any ideas. thanks

How many times has it gone stone dead? Every time that happens, it loses about 30% of its capacity, so it would be down to about 35% after three kills. If it froze while it was dead, that's even worse. That also presents a huge load to the alternator, which will run really hot and components will die. The field winding can get so hot that the enamel coating melts, which causes a loss of field strength because of the short circuit. The bridge rectifier, as mentioned, can fail, although that would manifest itself as a battery that dies in about three days when the boat sits.

If you have dirty or loose battery cables or the ground at the back of the motor is loose/corroded, it can't charge well.

If the battery is original, take it in and have it load tested, If the covers are removable, you'll see that a lot of the electrolyte is gone, even in a sealed battery.

bareinnj
07-25-2010, 09:14 PM
Battery is fine. Fires right up after sitting for weeks. Never dead, not even close. Battery is two years old, a good marine unit. I always "bump" the volts up right after starting. I have to believe the alternator is the prob. Belt tension is good. Wussy stereo. Volt meter in dash says no good, until I rev it out. As if the alt needs a kick in the arse to come alive.Thanks for replies, I appreciate the help and words of wisdom.

oldairboater
07-25-2010, 10:10 PM
One wire Alternator? Is this a new possible problem or did you just get paranoid? The alternator on two of my boats will not load up till the boat gets near 2000 rpm. It did this new and it did this rebuilt. Rebuilder told me it was normal so I never worry about it unless it doesn't jump up at around 2000 rpm.

JimN
07-25-2010, 10:13 PM
Battery is fine. Fires right up after sitting for weeks. Never dead, not even close. Battery is two years old, a good marine unit. I always "bump" the volts up right after starting. I have to believe the alternator is the prob. Belt tension is good. Wussy stereo. Volt meter in dash says no good, until I rev it out. As if the alt needs a kick in the arse to come alive.Thanks for replies, I appreciate the help and words of wisdom.

Make sure the charging and exciter leads are snug and the terminals are in good shape. If that doesn't help, I would take the alternator in to have it checked on a rebuild shop's "growler". They'll be able to get it up to speed. I wouldn't buy a new one- I think that wastes money for something that can be rebuilt to factory spec and I don't think I have ever had a bad rebuild from the shop I referred to in other posts. You should have someone near you who does the same kind of work.

JimN
07-25-2010, 10:15 PM
One wire Alternator? Is this a new possible problem or did you just get paranoid? The alternator on two of my boats will not load up till the boat gets near 2000 rpm. It did this new and it did this rebuilt. Rebuilder told me it was normal so I never worry about it unless it doesn't jump up at around 2000 rpm.

No, it has a separate exciter lead.

Most alternators won't provide a full charge until that RPM but most should be better than <12VDC at idle although a bad ground to the dash will make everything read lower.

thatsmrmastercraft
08-02-2010, 09:32 PM
I have encountered the same thing on my '77. It has a Delco Marine 10si one wire alternator that won't start charging until I hit 1000 RPM or so. Once it starts charging I can let it idle down to 600 RPM and it will put out 13.6 volts no problem. After every restart I have to bring up the RPMs to get the charge going.

On Saturday I had the boat out. Once launched I idled out of the channel where the boat launch is and idled across the lake to the beach. Just as I went to accelerate, the engine stumbled and died. It did not restart and had very little battery power to crank and very quickly ran out of cranking ability.

Once home and recharged with the battery charger, it fired right up. That is when I discovered the need to bring up the engine speed to get the alternator charging. I went through the alternator and everything looked good. The brushes had very little wear. I freshened up the surface the brushes ride on.

I suppose its possible that this alternator has always behaved this way and I didn't reach a high enough RPM Saturday to get the alternator charging and wore the battery down. Any thoughts on this?

JimN
08-02-2010, 10:36 PM
I have encountered the same thing on my '77. It has a Delco Marine 10si one wire alternator that won't start charging until I hit 1000 RPM or so. Once it starts charging I can let it idle down to 600 RPM and it will put out 13.6 volts no problem. After every restart I have to bring up the RPMs to get the charge going.

On Saturday I had the boat out. Once launched I idled out of the channel where the boat launch is and idled across the lake to the beach. Just as I went to accelerate, the engine stumbled and died. It did not restart and had very little battery power to crank and very quickly ran out of cranking ability.

Once home and recharged with the battery charger, it fired right up. That is when I discovered the need to bring up the engine speed to get the alternator charging. I went through the alternator and everything looked good. The brushes had very little wear. I freshened up the surface the brushes ride on.

I suppose its possible that this alternator has always behaved this way and I didn't reach a high enough RPM Saturday to get the alternator charging and wore the battery down. Any thoughts on this?

Measure the voltage at idle immediately after starting, without revving it up. Then, rev it to 1100+ RPM and look for the change in voltage. I suspect the regulator.

thatsmrmastercraft
08-02-2010, 11:37 PM
Measure the voltage at idle immediately after starting, without revving it up. Then, rev it to 1100+ RPM and look for the change in voltage. I suspect the regulator.

Battery voltage 12.6 volts immediately after starting. 13.8 at 1100 RPM and will hold the volts returning back to idle. Is this voltage regulator just lazy?

JimN
08-03-2010, 12:33 AM
Get a smaller diameter pulley for the alternator.

Jerseydave
08-03-2010, 02:51 AM
Battery is fine. Fires right up after sitting for weeks. Never dead, not even close. Battery is two years old, a good marine unit. I always "bump" the volts up right after starting. I have to believe the alternator is the prob. Belt tension is good. Wussy stereo. Volt meter in dash says no good, until I rev it out. As if the alt needs a kick in the arse to come alive.Thanks for replies, I appreciate the help and words of wisdom.

I agree with JimN, have the alternator checked out at a good shop.

Are you in NJ? If you're near Trenton, you can try Trenton starter and generator. They were always good to us when I managed a shop near there.
BTW, where do you ski in NJ?

thatsmrmastercraft
08-04-2010, 10:13 AM
Get a smaller diameter pulley for the alternator.

Had the boat out yesterday. Hooked my digital voltmeter an placed it so I could monitor it. As soon as the engine was warmed up I brought it up to 1100 RPM and the alternator started charging to 13.8 volts as usual. Ran wakeboarders up and down the lake for three hours without a problem. Volts were always high 13's to low 14's. Never dropped below 13.4 at idle.

The smaller pulley idea would do the trick. I may pop in a voltage regulator just to see if that takes care of it. Pretty cheap part to throw at it, and I don't think I would ever say "I wish I never replaced the regulator".

JimN
08-04-2010, 11:27 AM
Had the boat out yesterday. Hooked my digital voltmeter an placed it so I could monitor it. As soon as the engine was warmed up I brought it up to 1100 RPM and the alternator started charging to 13.8 volts as usual. Ran wakeboarders up and down the lake for three hours without a problem. Volts were always high 13's to low 14's. Never dropped below 13.4 at idle.

The smaller pulley idea would do the trick. I may pop in a voltage regulator just to see if that takes care of it. Pretty cheap part to throw at it, and I don't think I would ever say "I wish I never replaced the regulator".

I would measure the diameter of the pulley and find out if it's larger than normal. Gearheads used to get some free power from their cars and trucks by under-sizing the crank pulley because there's less resistance to the torque but the trade-off was that the alternator didn't start charging until they hit similar RPM to what you need. Any alternator rebuild shop should be able to get what you need. Usually, the one I go to asks what kind of pulley I need, and what size.

thatsmrmastercraft
08-04-2010, 11:29 AM
I would measure the diameter of the pulley and find out if it's larger than normal. Gearheads used to get some free power from their cars and trucks by under-sizing the crank pulley because there's less resistance to the torque but the trade-off was that the alternator didn't start charging until they hit similar RPM to what you need. Any alternator rebuild shop should be able to get what you need. Usually, the one I go to asks what kind of pulley I need, and what size.

I am headed there tomorrow with the alternator in hand. Thanks for the thoughts.