Thanks Maine! From available hunter documentation the h36 has a passivated SS shaft made of either Aqualloy or Aquamet. I think a $125 corrosion reference electrode is in my near future. The users manual is maintained by an ABYC person certified in corrosion.
Charles, my apologies for the confusing typos. My perceived problem is the two shaft zincs on my 1" SS shaft appear to be wasting away at a high rate that requires replacement on a 2.5 month interval. Our h30 would go about 8 months between shaft zinc changes. 2.5 months seems too short, but as Maine states, I don't have a B/A comparison on the h36 to see if the wasting rate changed suddenly or is normal. Until I discovered this problem, the refrigerator and battery charger remained on 24/7. I'm now turning them off when not at the boat until I figure this out. Bilge is dry now but obvious evidence of water in the past. Bilge pump switch and wires checked out ok - no shorts, opens or corrosion evident.
Calder's book explains the grounding system (bonded stuff) should be connected to the grounded system (DC ground) in order to prevent a potential difference between the two. Others say to separate them to prevent lightning current from passing thru the engine marine gear to the prop and sea. Calder does explain how to get around that. But the fact I have a potential difference of 70mV between the grounding system and the grounded system indicates the two are not tied together well, or not at all? And it may mean nothing with respect to rapid zinc wasting if those two systems are indeed electrically separate circuits. I can't make a reliable resistance measurement between the grounding system and grounded system because the existing 70 mV potential will fool the ohm meter since it places a small and unknown (to me) voltage/current on the component to be measured. But on the 200 ohm range the meter indicates about 40 ohms.
I'll be doing more cleaning of connections and troubleshooting over the next week while winterizing the boat and will report back. She's in the ocean year-round.
Charles, my apologies for the confusing typos. My perceived problem is the two shaft zincs on my 1" SS shaft appear to be wasting away at a high rate that requires replacement on a 2.5 month interval. Our h30 would go about 8 months between shaft zinc changes. 2.5 months seems too short, but as Maine states, I don't have a B/A comparison on the h36 to see if the wasting rate changed suddenly or is normal. Until I discovered this problem, the refrigerator and battery charger remained on 24/7. I'm now turning them off when not at the boat until I figure this out. Bilge is dry now but obvious evidence of water in the past. Bilge pump switch and wires checked out ok - no shorts, opens or corrosion evident.
Calder's book explains the grounding system (bonded stuff) should be connected to the grounded system (DC ground) in order to prevent a potential difference between the two. Others say to separate them to prevent lightning current from passing thru the engine marine gear to the prop and sea. Calder does explain how to get around that. But the fact I have a potential difference of 70mV between the grounding system and the grounded system indicates the two are not tied together well, or not at all? And it may mean nothing with respect to rapid zinc wasting if those two systems are indeed electrically separate circuits. I can't make a reliable resistance measurement between the grounding system and grounded system because the existing 70 mV potential will fool the ohm meter since it places a small and unknown (to me) voltage/current on the component to be measured. But on the 200 ohm range the meter indicates about 40 ohms.
I'll be doing more cleaning of connections and troubleshooting over the next week while winterizing the boat and will report back. She's in the ocean year-round.
