The only metal penetrating the hulls on an 1160 are the saildrives, the rudders, and the thru hulls.
Points of concern:
1. The thru hulls immediately transition to a plastic hose, so I am not very concerned about the thru hulls
2. The rudders are of slight concern as there is metal on the rudder stock which is exposed to sea water
3. The mast has wired running through it, so it should be tested too
4. Of course the biggie is the saildrives (and propellers)
Tools needed to perform cathodic testing of your boat:
1. Sg/SgCl (silver silver/chloride) reference electrode
2. High accuracy Multi-meter
Procedure:
1. Set your Multi-meter to mV
2. Place the Sg/SgCl reference electrode at the depth of the propeller off of the side of the boat
3. Check the voltage between the reference electrode and areas on your boat, my results:
- Port engine (on the raw water pump bracket), 1.072V
- Port saildrive (on the raw water inlet valve), 1.072V
- Port rudder stock, 0.126V
- Port holding tank thru hull, 0.111V
- Mast, 0.622V
- Starboard engine (on the raw water pump bracket), 1.072V
- Starboard saildrive (on the raw water inlet valve), 1.072V
I tested each point in the following electrical conditions:
1. Inverter ON, House batteries ON, Solar controllers ON, and Starter battery OFF
2. Inverter OFF, House batteries ON, Solar controllers ON, and Starter battery OFF
3. Inverter OFF, House batteries OFF, Solar controllers OFF, and Starter battery ON
Note: All tests performed while NOT connected to shore power
Note: All three power states above did NOT change the voltages measured at any of the points
Findings:
Typical for fiberglass boat is -550mV to -900mV, so I am a little high but I am in a high salinity water and the anodes are older. My plan is to retest in the fall with fresh anodes.
Note: I have a bonding strap that electrically ties the two sail drives together
Note: I have installed a Electrolysis Blocker between the shore power ground and the ships ground for isolation
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