A new Mariner 150hp is circa £13,600. A rule of thumb, and this pretty crude but generally gets you into ballpark is deduct 20% in first year of ownership, then 10% for every year thereafter. I'd pitch a guess at somewhere in £7-£7.5k territory, but that's just my guess.
The market is odd right now, so someone may be looking for a larger 4-stroke engine and service history to repower their current boat and may pay more given the cost against new. 1100 hours isn't excessive for a 5 year outboard, I've seen similar hp engines on FAFB with three times as many hours which will have had a hard life.
If you can provide engine print out from last service and compression test, then that all helps towards selling. Hopefully the paintwork and cowl are mint.
Another option is call Cameron at Clyde Outboards. They charge £25 for a valuation which I think is pretty decent and that's from a marine engineer.
Sula
