Conference unifix::sailing

1434.0. "Gray Marine alternator upgrade" by VLNVAX::FRENIERE () Wed Jan 24 1990 11:55

    Gray Marine engine owners. If you are still pleased with that
    hunk of iron like I am, but have battery charging problems, take
    notice.
    
    I have a Gray Sea Scout, 25 hp. It happens to have a fresh water
    heat exchanger, so I am running two water pumps now. It is the type
    of engine which drives an automotive type GENERATOR (not an
    alternator). The shaft of the generator also extends out the rear,
    and through a universal, drives the brass seawater pump. This and
    several other varieties of Gray engines use this method of charging
    and running the seawater pump off one pulley.
    
    Much trouble trying to keep my batteries charged. To run at night
    with the engine off, and just occasional uses of interior lights,
    maybe a few minutes on the spreader lights, and the same for the
    spot light, would mean, over three hours, a drain of some 26 amps
    that had to be replaced. Now with the old generator, and the engine
    flailing away pumping a whole 10 amps, would require two and ahalf
    hours to restore the batteries. That is, except for the fact that
    the rate of charge soon dropped off due to the regulator. Thus the
    batteries were never really ever brought up to charge.
    
    So, what to do. I have designed a heavy duty fixture that acts as
    an intermediate shaft to drive the waterpump from a pulley placed
    in the same position as the now removed generators. Also on this 
    intermediate shaft is a second pulley. It is connected by a short
    belt to a marine alternator. This alternator is mounted on the
    plate that supports the bearings for the imtermediate shaft. This
    plate has the same mounting holes as the original generator bracket.
    Thus I can swing the unit to adjust tension on the driving belt
    from the flywheel. The alternator itself  is adjustable to adjust the
    tension on its belt. The pully driving the alternator belt is 4"
    so that there is a higher alternator speed to allow charging at lower
    engine speeds. 
    
    I am installing it this weekend on "Hope". Combined with a manual
    alternator charge controller and regular unit, I expect to get my
    charging down to a half hour a day at the most. This is especially
    important as I am now swinging on a mooring, so the engine is
    seldom used.
    
    If any one of you would like to get more information, contact me.
    The unit is quite simple but rugged. It has to be built in a machine
    shop because the bearing housing requires press fits, etc.
    
    Don

    As an added note. The generator cases on the old Grays are open.
    That means they are a source of electrical arcing. You should
    always pay the premium and use an alternator rated as "Marine.."
    This indicates that the brushes of the alternator are shielded such
    that there is no arcing....
    
    In another note, it was reported that the gases driven off the
    batteries during charging can reach an explosive mix. I gather
    the danger here is in fooling around with the leads when charging.
    Or is there sufficient gas that it could lay in the bilge and be
    an explosive hazzard?
    
    Don

>    In another note, it was reported that the gases driven off the
>    batteries during charging can reach an explosive mix. I gather
>    the danger here is in fooling around with the leads when charging.
>    Or is there sufficient gas that it could lay in the bilge and be
>    an explosive hazzard?
    
The gas given off is hydrogen. It is very light and will seek the great
outdoors, rather than the bilge. (unless your boat has capsized :-)

--RS