The solution
Claude: No problem in cleaning up that drawing--it wasn't mine but yours is much easier to understand now.
Andre: The relay numbering is pretty standard. I think this is what the terminals should be wired as (should be a pictograph screened on the relay housing - 85/86 are the relay coil):
30 = Fused with 30 amp fuse (equal to the RS relay's rating) to a heavy positive power lead - 10 AWG - (taken from the battery lead [big post] on the starter)
87 = Terminal on starter relay where starter button wire was connected
85 = Wire from the starter button
86 = Black wire to ground
The picture shows the fuse wired between the relay and the starter solenoid. I feel it shoud be on the incoming current lead side into the RS relay instead--how I've wired it on my boat. The RS relay wiring pictured is mostly white, but the black one is definately to ground.
Hope this helps
I was one of the very early boats (my 40.5), that had the intermittent starter problem.
Changing wire guages, and all that, is a total waste of time.
The correct, and only, solution, is to install the relay.
Any high current relay will work. The drawing using the solenoid is 100% correct, and will work flawlessly.
It was interesting that Yanmar said "they never heard if the problem", which was total BS. It wasn't just Hunter owners. Beneteau guys had the same issue.
I found a 100% predictable way to know exactly when the engine would fail to start. Very scientific test, with exact parameters:
Go out sailing
On way back in, enter restricted water way, such as channel
Wait for wind to gust up to 25 knots.
Now, stand by, and wait for the exact moment for a freighter to bear down on you.
Turn key.
Curse loudly as engine doesn't start.
Now, with panic setting in, round up to wind, and with headsail flogging, try & furl in.
Curse more.
Try not to notice large freighter, and try key again.
Now bear downwind, and get out of channel.
One last time, try key.
Vroom!
Apologize to wife for previous tone of voice when she mistook furling line for topping lift.