I have a 1988 Wellcraft St. Tropez 32' cruiser with twin 1988 Mercruiser V8 454's 340HP inboards, Borg Warner transmissions, Thunderbolt IV Bluewater
ignition system, distributor (not points).
I have 1 starting battery
(Group 29, I think) that feeds both engines via my battery
selector switch. (Yes, really, only 1 battery wired to two engines.) My other battery is a 4D deep cycle house battery. Of course, from my one and only battery selector switch I can select 1, 2, or all batteries
, and whatever I select will feed BOTH engines simultaneously. My point here is that with the current
setup, I have no way of specifying which battery goes with which engine
The port side has a working alternator
. I know because when tracking down an issue last year I broke part of the housing on the old (probably original) alternator
and replaced it with a new alternator. I also know because when revving the port side I can see the voltmeter (on both engines, mind you!) go from around 12v to more than 13v indicating it is putting out a charge.
The starboard side alternator (the one in question) seems to not do anything at all. When I rev the starboard engine
, the voltmeters don't move, at all. I've also checked with a multimeter and there's no detectable output from the alternator. Of course this means that if my port side motor
ever fails and I have to get home on just the starboard side, I'm generating spark from my battery and can only go as far as it will take me until it dies. That's not a risk I like, especially with older motors...
There's disagreement among my boating
friends as to whether or not the starboard alternator is broken (diode, perhaps?) OR if it is a "dummy alternator" -- a fake there just to have the pully for the belt to go around.
Friends who think it may be a dummy alternator defend their position by saying they think it would be "wrong" (and perhaps dangerous) to have TWO alternators on separate engines simultaneously charging
ONE battery -- and possibly each other! I can understand what they're saying here.
Dummy alternator or not, I've been thinking about replacing the non-working starboard alternator with a new, working one. But I'm a bit concerned about having both feed the battery, AND/OR each other.
A close boating
friend who is an electrical engineer
thinks my boat's electric
setup is "weird." I'm not sure I disagree. But, it is what it is, at least, until I change it. He thinks I should add a second starting battery and isolate the two engines each with 1 starting battery of their own, AND put in a crossover switch in the event that one side's battery dies and I need to start it. (While still having the deep cycle 4D house battery, but I'm unclear as to how that would get hooked up.)
What do my fellow CruiserForum readers think? Have I described enough of the story here? What would you do? Just replace the starboard alternator? Is there any risk? Would you rewire anything as part of the job? Should the two motors be electrically isolated in some way that they're currently not? Should I add a battery and isolate the two motors?
Looking forward to hearing what you all think. Thank you in advance!