Alternator

[Endless Summer]

The alternator is not kicking in until about 2000rpm is this normal? I have had the boat for about a year now. The engine type is Volvo 40A diesel.

[yellowfin1]

Has the boat been sitting for a while? If I've had Tenacious sitting/not running for a couple months sometimes the alternator guage shows the RPMs bouncing around or sticking. Also check the wires (especially the ground) on the back of the alternator. A suspect connection or some corrosion might cause that.

[Wa Mei]

The alternator is not kicking in until about 2000rpm is this normal? I have had the boat for about a year now. The engine type is Volvo 40A diesel.

Brings back bad memories from a couple year back...

I ended up having the alternator rebuilt twice by Lewco. Bad crimp on the
positive wire broke. Can't tell because of the heatshrink covering the
crimp. Found it when I went to 4/0 wire instead of the 10awg wire
while installing the rebuilt generator. Bad connection will blow the regular.

2nd time around, my ground wire to the battery was loose which end up
blowing the regulator and melting the battery post.

I would suggest you triple check all connections. Make sure they are not corroded and tight!

Back to your question of alternator not kicking in until after 2k rpm. Are you
saying that your tach is at zero and jump to 2k rpm or the voltmeter is at
zero until you get to 2k rpm?

[NoSlack]

On the 40 engine the tach does not come off the alternator. I think he means the engine has to come to 2000 RPM before the alternator starts producing.

When I get home I'll edit this reply with a picture of the resistor location and wire color code that controls the excitation of the old style alternators.

Your looking for a rectangle box that hangs in a bracket on the back of the oil pressure gauge. The green wires go hot when you turn the key on and the black wire on the other end of the resistor goes down to the excitation post on the alternator. The resistor on my spare engine reads 69 ohms. You can also check the connections on the plugs for the cable that goes from the gauge panel to the engine.

I'm not sure how the resistor affects the excitation of the alternator, but at 69 ohms it work and with the resistor disconnected it doesn't.

http://members.cox.net/bocaboard/IM002025.JPG

http://members.cox.net/bocaboard/IM002023.JPG

I upgraded to a self exciting alternator a couple years back and it starts producing just over 800 RPM on the engine.

Mike

[Endless Summer]

Brings back bad memories from a couple year back...

I ended up having the alternator rebuilt twice by Lewco. Bad crimp on the
positive wire broke. Can't tell because of the heatshrink covering the
crimp. Found it when I went to 4/0 wire instead of the 10awg wire
while installing the rebuilt generator. Bad connection will blow the regular.

2nd time around, my ground wire to the battery was loose which end up
blowing the regulator and melting the battery post.

I would suggest you triple check all connections. Make sure they are not corroded and tight!

Back to your question of alternator not kicking in until after 2k rpm. Are you
saying that your tach is at zero and jump to 2k rpm or the voltmeter is at
zero until you get to 2k rpm?

It doesnt kick in until the engine gets to 2k.

[Endless Summer]

On the 40 engine the tack does not come off the alternator. I thing he means the engine has to come to 2000 RPM before the alternator starts producing.

When I get home I'll edit this reply with a picture of the resistor location and wire color code that controls the excitation of the old style alternators.

I upgraded to a self exciting alternator a couple years back and it starts producing just over 800 RPM on the engine.

Mike

That would be great. Thanks

[Endless Summer]

Hi Mike,
When you upgraded the alternator did you replace it with a one wire alternator? I put one on an older skipjack I had and it worked great. I am still having issues with the one currently and thinking of just replacing it with the same type.


On the 40 engine the tach does not come off the alternator. I think he means the engine has to come to 2000 RPM before the alternator starts producing.

When I get home I'll edit this reply with a picture of the resistor location and wire color code that controls the excitation of the old style alternators.

Your looking for a rectangle box that hangs in a bracket on the back of the oil pressure gauge. The green wires go hot when you turn the key on and the black wire on the other end of the resistor goes down to the excitation post on the alternator. The resistor on my spare engine reads 69 ohms. You can also check the connections on the plugs for the cable that goes from the gauge panel to the engine.

I'm not sure how the resistor affects the excitation of the alternator, but at 69 ohms it work and with the resistor disconnected it doesn't.

http://members.cox.net/bocaboard/IM002025.JPG

http://members.cox.net/bocaboard/IM002023.JPG

I upgraded to a self exciting alternator a couple years back and it starts producing just over 800 RPM on the engine.

Mike

[NoSlack]

I installed a Motorola 110-603, 90 amp alternator. The 110-656 is a 55 amp.
http://www.spidermarine.com/UserData/Images/Medium/105140.jpg

No more excitation wire, but you'll need to upgrade the positive and negative wire to carry any more current than the stock 35 amp with a number 10 wire. It kicks my volt meter up above 12 at 800 RPM and tops out at 13.5 before I reach 1000 RPM.

The stock one is a 35 amp, so replacing the old one with a self exciting 35 amp would be real easy. If you go with a 55 amp, change the wire to a fine strand #8 and a fine strand #6 for a 90. Also put a straight edge on the pulley to make sure they line up. I had to shim my new alternator forward a 1/4" to get the belts in perfect alignment from pulley to main pulley.

Mike

[Endless Summer]

Thank you, I am going to order one.