I’ve got my Boat Safety Scheme inspection coming up in Spring ’25, so had a look at the engine bay wiring to see if anything needed sorting. I was aware the alternators weren’t in great shape after the guys from HiQ Marine serviced Lizzy and checked everything over for me. I’d also noticed the general state of the 12v wiring and was keen to get that straightened out.

Main Image – the pile of junk removed

A BSS test fail for so many reasons; bad battery terminals without covers and the starter/alternator wires were too thin. Also a potential fire hazard due to terrible cheap inverter that can’t decide how powerful it actually is, some terrible distribution and crimping and most of it was wired with 8AWG which is less than 10mm² and not up to the job even if it was properly terminated.

Control Panel

Lizzy has a 1.8 BMC engine and has two alternators now, but the old split charge wiring is still there and apparently still live.

Starter Alternator Wiring

Two different and confusingly coloured wires using the crimps on the A127 type alternator instead of that lovely fat B+ post right there, then stuffed into one crimp on the battery. Battery to starter cable was 16mm², stuffed into battery terminal and badly crimped to isolator, the earth 16mm² and badly crimped. Tacho/hour counter don’t work, possibly because the “W” terminal on the alternator has no lead attached.

Leisure Alternator Wiring

This appears to be a Delco Remy DRA4652 off a Vauxhall Corsa! Wiring actually not that bad, but not charging properly despite the freshly reconditioned alternator. OK maybe it is that bad – only 8AWG (<10mm²) cable stuffed into the battery terminal and rusted.

General Mess

The red wire entering stage left comes across the engine bay from the leisure battery bank on one unfused, badly terminated 8AWG wire which has a max 70a capacity. It splits off to the bilge pump wire with an inline bodge and then uses the isolator as a cowboy bus bar. The three red wires then went to:

1. The crap inverter that could pull 114a, via a badly crimped isolator with no strain relief and 30a car audio fuse
2. The main fuse box for cabin lights/pumps/horn/headlight
3. A feed that bypasses the fusebox and runs the length of the cabin, which was firstly connected to another inverter powering the fridge. Under the sink. Then daisy chained off that to the front door area where the TV used to be.

The negatives were all attached to a bus bolt and left dangling and uninsulated below the boat controls.

Summary

While I knew there were a few issues, the wiring turned out way worse than it looked. Half of the connections fell apart easily and the main feed was way under spec for the installed inverter. I’ve replaced it all with properly terminated, fatter cables now following this diagram I worked out and drew in Sketch – thanks to the 12v Boating Group on FB, NOHMA and Explorist for all their great advice and diagrams.

This has all made the engine bay wiring safer and the water pumping much harder without dimming the lights. Next stage might be a Victron EasyPlus inverter/charger and 400w solar setup. Although I live in the marina on shore power it would be nice to have the auto switch of the inverter/charger to protect my computers if and when the power drops out due to maintenance or flooding.