OK thanks - I'm thinking it's likely a solenoid with damaged coil, and checked into the part from Volvo Penta (part 876614) ... over $500!
It's a Bosch solenoid Part#RD 0330 001 015 and I found it on eBay for $34, with free shipping. For that money I bought it as an opportunistic purchase... figure it's small and good to have in the boat's spares kit even if it's not the issue. Definitely not something I want to buy from Volvo Penta.