If it’s not the relays (fuse) maybe the switch itself on the throttle quadrant.....relays are the most likely cause and it seems you already isolated that....mine sometimes requires a whack on top to wake it up. Mine is a few years older, but could it be a low level switch associated with the hydraulic fluid reservoir?
I would try and jumper the switch if possible to isolate that...should be a schematic or write up somewhere on the internets
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Jon Miller
1998 four Winns Horizon H200
Volvo Penta 4.3 GL
Newtown, CT
untitled-545 by
millerjont, on Flickr