KAD42 Charging problem

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targa31

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Set up is twin KAD 42's with 3 batteries. Starboard engine - All voltages normal at tickover but when revs increased under load to 2500+ voltage drops to below 12v (on guage)? Sometime guage flicks around a bit? Starboard only. Belt seems ok, no noise etc or excessive slackness. Any ideas much appreciated. Thanks in advance.
 
targa31 said:
Set up is twin KAD 42's with 3 batteries. Starboard engine - All voltages normal at tickover but when revs increased under load to 2500+ voltage drops to below 12v (on guage)? Sometime guage flicks around a bit? Starboard only. Belt seems ok, no noise etc or excessive slackness. Any ideas much appreciated. Thanks in advance.
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Check all connections and brushes and slip rings

Get alternator checked by an auto electrician
 
I think you will find the main belt from the crankshaft up to the waterpump is slipping, as this then drives the alternator and compressor via the pulley on the waterpump and its probably the load imposed by the compressor thats loading it up making the main belt slip.
 
spannerman said:
I think you will find the main belt from the crankshaft up to the waterpump is slipping, as this then drives the alternator and compressor via the pulley on the waterpump and its probably the load imposed by the compressor thats loading it up making the main belt slip.
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It's easy to check this by unplugging the supercharger clutch plug.
 
I had the same issue on my last boat (twin kad42 on a sealine F36)

Turned out to be alternator

Used these people
http://www.remanufacturers.co.uk/prod-xf/detail.asp?imer=AL0505 This should be the correct one around

Very cheap less than £90 delivered

Ended up replacing both alternators within 6 months of each other. With the unit as shown above but you will need to change over the pulley from the old alternator.

Did around 100 hours in a year, before we sold her last August. .
 
An update.....Tensioned all belts and all working fine when in neutral (at any revs) - voltage indicating about 13.3v at tickover. When get onto plane voltage indicated drops to less than 12v? (revs were 3000). Even though the battery spun the starter motor fine so presume battery is OK? When adding a bit of trim tab voltage increased to approv 12.5v then dropped again as soon as finger released from trim switch? As soon as down to 1200 revs voltage goes back to 13.3v?

Can i presume twin engine set up would charge all 3 batteries if 1 alternator is not working as it should?

Any ideas would be appreciated - thanks in advance?
 
targa31 said:
An update.....Tensioned all belts and all working fine when in neutral (at any revs) - voltage indicating about 13.3v at tickover. When get onto plane voltage indicated drops to less than 12v? (revs were 3000). Even though the battery spun the starter motor fine so presume battery is OK? When adding a bit of trim tab voltage increased to approv 12.5v then dropped again as soon as finger released from trim switch? As soon as down to 1200 revs voltage goes back to 13.3v?

Can i presume twin engine set up would charge all 3 batteries if 1 alternator is not working as it should?

Any ideas would be appreciated - thanks in advance?
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Are you measuring the voltage directly on the batteries or are the reading from the voltage meter on the dash?
 
unfortunately due to nature of the issue (only seems to happen at speed?) only taking reading from the dashboard voltmeter.

Plan to go to boat this morning to 'clean' the contacts on as many connections as possible.

Any ideas?
 
I would start with measuring the voltage with a multimeter directly on the terminals or as close as would be feasible while driving.
It could very well be something with the cabling to the dash.
 
thanks,

I have been down this morning and cleaned all the connections to the voltmeter.

Tested with a multimeter at the voltmeter and get 14v at tickover and 3000 revs. Drops down to 13v when the supercharger is on.

This is the same as the reading on the voltmeter.

Will see next weekend if that has resolved the issue. Good idea about the multimeter. If problem not resolved i will connect flying leads to the battery so i can test what is going on at speed.

thanks again.
 
If the voltage goes down when the supercharger engages then your belts are slipping, I would make sure they are ok before spending more time on the generator and cabling.

Also if it's a dodgy connecting/cabling issue it may only show when the boat is moving about which was why I suggested you measure using a multimeter while driving.
 
Belts feel pretty tight to me so i think it might be a trip to RK marine tomorrow to get some new belts. There is a bit of dust around. Do belts slip more when worn?

See what that does.

Any tips on tensioning new belts?

cheers
 
I change mine every couple of years so don't know what happens when they get really old and still in one piece but I imagine the rubber gets dry and don't grip as well so maybe that's why yours slip.
The dust is a sure sign of the belts slipping and in terms of being tight I think I remember mine feeling tight but still slipping at one point, not sure now but think that you adjust the tensioner to between 37-41 nm on the newer type belt tensioners. When new you re-tension them after a couple of "hot" runs.
 
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