My buddy purchased a boat that has a 1989 Yamaha ProV 150 on the back but no lower unit. It's a 20" shaft engine and wants to purchase an SEI lower but not sure if it's a 1.86:1 or a 2.00:1

Anyone got an idea? It's on an old Switzer craft and it weighs next to nothig so I would assume the 1.86:1 will work fine but don't want any issues proping it.


Thanks
Joe