I have had a problem with my batteries gradually running down as I use the boat during the season last year and again this so I started running a few tests. The Clymer "official manual" is next to useless as it details method for testing volts and amps but advises that it is not possible to service the alternator yourself and get professional help. Volts did not differ across the battery terminals whether the motor was running or not so pretty safe to say there was no charge reaching the battery so took alternator to specialist auto service repair and they claim it is a candidate for exchange - at £91 plus vat I am happy with the solution BUT: Various comments I have seen suggest the 35amp Hitachi that is standard for the Yanmar does not give enough charge to keep up with modern equipment such as chart plotters and full instrument deployment. Any thoughts?

David Tilley

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Hello David
Beware of fitting larger alternators on the GM10, we thought we had problems with our engine on Bright Eyes, it would run with all sorts of black smoke billowing from the exhaust and eventually choke itself to a stall. On one occasion I jump started it from a single battery as the boat's batteries were flat and it ran fine.
What was happening was that the engine had been fitted (not by me) with a 70amp alternator and when the batteries were very low the charge load was too much for the engine, if I charged the batteries from a shore line prior to starting it also ran OK. I would suggest you could try 50amp but be aware of the problems I mentioned. But the 35amp alternator should do unless you are running a fridge all the time.

Jan Newman
Blue Moon 325/32

Thanks for the reply Jan, I have since fitted the new 35amp Alternator and the batteries indicate 12.60V when fully charged and 10.6 under load of starting which is said to be a healthy range however there are still odd occasions when the initial push of the starter button will not turn the engine over on the fist try. Subsequent attempts have always proved successful but I'm wondering if the "Staring Bull" 40a/h battery that was fitted by the previous owner may be a bit light. I am redoing the woodwork around it this winter and don't want to make the space fit this battery if I need to replace it with a bigger one for piece of mind.

David Tilley

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Hello again David
I would be tempted to plan for a bigger battery, more margin for error or better still two, then you can keep one for starting purposes, 275's have two. I was interested that you report a reluctance in the starter engaging, we notice this when the batteries are going down a bit, no problem on full charge, so we keep the "Starting" battery fully charged and only use it for starting.

Jan Newman
Blue Moon
325/32

Hi Jan,
Yes I do have two batteries and a VSR control so that the starter charges before the house. The starter motor does engage but does not seem to have enough oomph to turn over the engine on some occasions and my theory is that when that happens the solenoid engages on the compression cycle and therefore the starter does not have a chance to gain momentum before the full resistance of the compression engages. This does not happen if I have had the battery on a shore power charger but the new alternator is pumping in almost 14 volts so I am left with a conundrum: It always does seem to start eventually but I like things to be perfect!

Signed, Doomed to a life of disappointment!

David Tilley

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quote:

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Originally posted by David Tilley

Hi Jan,
Yes I do have two batteries and a VSR control so that the starter charges before the house. The starter motor does engage but does not seem to have enough oomph to turn over the engine on some occasions and my theory is that when that happens the solenoid engages on the compression cycle and therefore the starter does not have a chance to gain momentum before the full resistance of the compression engages. This does not happen if I have had the battery on a shore power charger but the new alternator is pumping in almost 14 volts so I am left with a conundrum: It always does seem to start eventually but I like things to be perfect!

Signed, Doomed to a life of disappointment!

David Tilley

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Dave,

I have a P275, and in the search for better battery life I first fitted an Adverc charge controller, which helps improve the charge rate. I have now fitted an engine start battery, this is a Red Top 25 AGM battery which is very light and compact, and can be fitted anywhere. This leaves the other batteries for domestic use.

The 35 amp alternator seems to cope ok - the use of the charge controller, rather than the standard regulator in the alternator means that it delivers more amps to the batteries.

Dick
Dark Star P275 No 36

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