SEI SE404 Lower Unit for Yamaha 4-Stroke Outboards 2.3:1 RatioThe SEI SE404 is an aftermarket replacement lower unit for select Yamaha four-stroke outboards requiring a 2.3:1 gear ratio. Available for 20" and 25" shaft applications, each unit comes in black and can be painted to match your engine. Choose the shaft length and confirm the full engine model to select the correct replacement.This item is subject to a 20% restocking fee.Year, serial number, and horsepower are required to process your order. Please contact us with this information after placing your order. Processing will be delayed until this information is received.Features Aftermarket replacement lower unit from SEI Marine; For select Yamaha four-stroke outboard applications; 2.3:1 gear ratio; Available for 20" and 25" shaft lengths; Black finish that can be painted to match; Applications by Shaft Length 20": Select Yamaha F75, F80, F90, and F100 four-stroke applications; SEI part number 90-404-B20F; 25": Select Yamaha F80, F90, and F100 four-stroke applications; SEI part number 90-404-B25F; Fitment RequirementsDoes not fit 2016-and-newer four-stroke engine models ending in "B". Confirm your full Yamaha engine model number against SEI's application guide before ordering.Verify your engine year, serial number, existing gear ratio, and shaft-length designation. Horsepower alone does not establish compatibility.Replacement References 20" version: Replaces OE part number 6D9-45300-10-4D; 25" version: Replaces OE part number 67F-45300-30-4D;