I'll be the first to admit that I'm a bit deficient when it comes to electrical know-how on my boat... learning though. Anyhow, I've had it for around a year and a half, and recently installed new AGM batteries: a pair of parallel group 31 (house) and a group 27 (starter). I just noticed (after only a couple uses this season) that when I run the engine, my voltmeter at the circuit breaker panel reads 13.5-13-6 but I'm pretty sure that in the past (last year) it would read somewhere in the low-to-mid 14s when the engine was running. I checked the specs on the batteries, and they want to charge in the 14s. Further proof that I'm correct to be worried about 13.5 is that even after running the engine/alternator for a while (30-60 minutes), the batteries only read in the low-to-mid 12s for voltage, (up from high 11s when I start the engine) rather than around 12.8+ where they ought to be. I don't want to damage my new batteries. The alternator is a 60amp (original) alternator on a Yanmar 3YM30 engine, and as far as I can see the wiring everywhere seems to be in good condition, no corrosion or lose fittings that I could spot. Things I found in investigating/troubleshooting:
Is there more troubleshooting I need to do, or is the next step to buy/install a new alternator? It's about 15 years old (though only a few hundred hours), so I'm okay slapping on a new one if that's what's best. I suspect paying someone (northeastern USA) to disassemble/rebuild it will cost me nearly as much as buying a new one. I suppose I could keep the old one as a "spare" and tinker with it myself to see if it is repairable... I'm generally pretty handy even though alternators aren't an area I've dabbled before. What votes the sailors of the interwebs? Buy a new one? Do more testing? I'm a fool? Fix the old one? If I'm to buy a new one... I don't need a bigger one (IMHO), but... any advice on replacements to steer toward or away from? Thanks!
- Same results, whether I've got the house, or starting (or both) batteries switched on.
- Same results whether I run the engine at say 1200RPMS or 3400RPMS (just for testing... I don't normally run it at that speed)... and neutral vs in-gear also makes no difference.
- I tried with everything switched off (no extra loads like fridge, or pumps, etc.) still no difference.
- I measured both at the panel itself, and also used a multi-meter to test across the back of the alternator when it was running... same (or negligible difference)... so I don't think it is voltage loss over the harness/wiring.
- I have a mooring, not a slip, so no electrical hook-up, but recall when launching at the boatyard weeks ago I DID use shore power, and using my on-board charger was charging batteries fine at somewhere in the low-mid 14s, and the batteries would go up to where they should be.
Is there more troubleshooting I need to do, or is the next step to buy/install a new alternator? It's about 15 years old (though only a few hundred hours), so I'm okay slapping on a new one if that's what's best. I suspect paying someone (northeastern USA) to disassemble/rebuild it will cost me nearly as much as buying a new one. I suppose I could keep the old one as a "spare" and tinker with it myself to see if it is repairable... I'm generally pretty handy even though alternators aren't an area I've dabbled before. What votes the sailors of the interwebs? Buy a new one? Do more testing? I'm a fool? Fix the old one? If I'm to buy a new one... I don't need a bigger one (IMHO), but... any advice on replacements to steer toward or away from? Thanks!