Solenoid Clunks

Thank you for that; an interesting read.
The approach then is that as the engine start is a push switch I could disconnect the wire at the starter and behind the switch and replace it with a heavier gauge, single wire.
I could also add into that circuit a relay?
That's what I did, without the relay. Post #13.
 
To conclude this…
It would appear that this is a known issue with Yanmar 2GM looms as there are so many breaks and connectors between the battery, panel and starter. There’s a few threads on here and some videos on YouTube.
I had the starter checked and a new solenoid fitted (shout out to A Star Auto’s in Sussex) to rule that out and also fitted a new Bosch starter battery (the original was dated 2014 so needed changing really).

The upgrade that seems to be common is indeed a relay and new wiring. So for any other 2GM owners out there…

Everything I fitted was rated above 30a. All wiring was 6mm2 (10ish AWG), timed and supplied by 12v Planet.
I replaced the starter switch on the panel with a new one. The old one had soldered terminals, the replacement has screw terminals for 4.3mm ring terminals.

I disconnected the original grey wire that runs from the switch to the low voltage terminal on the starter and replaced this with one length of new wire from thr switch to a relay (86) with the corresponding terminal (85) wired directly to the battery -ve.

The ignition switch now solely operates the relay.

I took a new cable directly from the ‘hot’ terminal on the starter, that’s also connected to the alternator, to the relay (30) via an inline 30a fuse. This is now the feed for the solenoid.

To complete the circuit I took a cable from the relay (87) to the small terminal on the solenoid where the original grey cable used to feed power from the switch.

All fine now and the starter engages much faster.

What I learned from this is that the ‘low voltage’ feed from the ignition switch is needed to keep the starter dog engaged with the flywheel, I’d always assumed there was an internal relay that did that, and this can pull some amps, which combined with the voltage drop in the cable run with all those connectors is a less than ideal setup.

The modification cost £40 including next day delivery from 12v Planet and plenty is spare wiring…. Plus a very enjoyable afternoon, I quite enjoy electrics!
 
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