I know there are some very smart people out here on OSO so here is my question. Using an example of 900 hp with bam trannys and wet sump 6 drives or dry sump what is the horsepower loss from the crank shaft to the prop either in percentage or numbers? Thanks for the info.

well... there is no simple answer for this because everything changes everything . measuring it on a percentage basis wouldn't be possible unless you knew the precise loss numbers of the " driveline" because they will remain constant although that value alone can be dramatically affected by temp and lube type... but for simple numbers you can say that what the drive line uses will be a constant... so it doesn't matter if its a 900 hp motor or a 500 hp motor... if the driveline needs 100 hp to run it at 4000 rpm then thats what it needs. that would be 20 % of a 500 hp motor and about 11 % of a 900 hp motor... so see? that number will float

so really .. is your question " how much hp does a bam transmission with a # 6 and X prop use at y rpm at z temp using q lube use ?? "

bam should be able to tell you the answer for the transmission. merc should be able to tell you the answer for the drives and simple math will tell you about the prop once you know its mass and diameter and MOI. then you just add them up and you will be close...