Valhalla Jeremy wrote: Hi Kandrew, do you leave the terminals on for this check? |
Valhalla Jeremy wrote: Hi Big Dave did he say how he does the check itself?? |
Alan L wrote: So I checked my voltage today - battery + to the hull. I got full battery voltage. The boat has always had slight signs of corrosion - it is near 20 yrs old. I am waiting right now to get a bit of welding done to fix a couple of corrosion spots - first repair job. But this seems to indicate my hull is earthed to the motor? But I struggle to see how else it could be. The motor is bolted to the hull via 4 large stainless bolts - which must be excellent earth connectors? What else should I be doing? I fitted zinc anodes to the hull some years back. Regards Alan |
Alan L wrote: The exterior of the hull is painted. Can send a pic if useful. The interior is not painted. There has been on going micro pitting in many places, and in a few spots after being stored for a bit there is some white gel like spots. But it has done near 20 yrs now and the first repairs are required. But I wonder if there is something else I should be doing. I was looking for mV reading. Off scale. Got same V as direct over battery. And the isolating switch is Off. Regards Alan |
Alan L wrote: Yes the 12.7 V is with isolating sw Off. I am very particular about fish hooks, gaffs etc. Not so much when fishing - but when boat is stored. I even isolate the anchor and chain from the hull. I have stripped the hull out a week or so ago - checking, and no extraneous crap under there. Clean. Totally. I could probably isolate the motor - but that will take some teflon washers (easy) and drilling the bolt holes o/size and sleeving the bolts via something. Not sure how secure the motor will be, but could be done. I would have to have a closer look , but the motor is buffered by rubber mounts (between the steering pivot and power head). Whether this isolates it completely I haven't investigated (Merc 90 2S). I don't clean my boat - at least not with dishwash stuff etc. And generally, not much. Hose down, fresh water. Enough to get the blood out. To get more on topic, I am not sure the hull has deterred any gamefish. Maybe could always be more, but I have had mahi, wahoo and marlin swim right under the boat. Had a YF jump about 20m in front a couple of days ago. So I am not sure what to make of that stuff, but I am concerned about electrolysis and the hull more than scaring gamefish. Regards Alan |
Bigfishbob wrote: So up to January this year we had trolled about 500 hours and seen/hooked one Marlin. I had a few chats with Jeff Scott who has a auot electrical business at Tauranga and works on mostly boats. Is regarded as one of the gurus of this type of stuff. He recomended fitting a 3" tear drop annode to my hull. Believe it or not the very next day we went out and caught a marlin. I then got the boat over to him a couple of weeks later and he would normally test for three things but given I have a fairly new, 3 years old, engine, he only needed to do check for electrical leakage to the hul, then the cathodic balance of the hull. For electrical leakagae, he found that the Car stereo that the previous owner of the boat fitted to teh hull was grounding to the hull. So I have now insulated that using insulated bushes. The second issue is that the fuel sender had earthed itself to the hull. So we disconnected that and now I track fuel usage from the engine management system. The next step is cathodica balance. In effect you boat is made up of dissimilar metals Aluminium and stainless, and when you put them in an electroclyte,Saltwater, the hull itself becomes a battery and generates voltage. Ideally an aluminium hull should generate 900-930 millivolts and fitting the zinc anode balances the dissimilar metals to get the voltage where it needs to be. They test this using a device that hangs a probe into the saltwater beside the boat, and touching the otehr probe to teh hull. It turned out that the anode I had fitted was dead right and my voltage was just over 900 millivolts. We went on to get another marlin to the boat and had another 7 hookups that weren't landed. So we had a much better season. TBH, we also used SST charts for the first time this season so we could well have been fishing in better places. But at the end of the day, knowing that these issues are sorted on your boat is always going to help. |
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