hi,
i just ordered and recieved a used lower unit for my 1979 mercury 50hp outboard. it is a different gear ratio than the original that came on my motor.
when i turn the new lower unit input shaft it takes aprox. 1.65 rotations to turn the prop once. on the original lower unit it is almost exactly 2 rotations of the input shaft to turn the prop once.
with a 14 pitch prop on the original i could run close to 30mph, as in GPS would say 29 then 30 and back and forth with 2 people onboard my 16ft flat bottom at 5500 to 5600 rpms.
i ordered a new prop for the new lower unit and i ordered a 15 pitch to drop rpms alittle, well this was before i realized i had a different gear ratio. it will push the boat at 18mph at 3800 rpms with just myself onboard. i was thinking the new prop was a different design or something and ordered a 13pitch prop it will run about 23mph at 4300 rpms.
with my new lower unit and gear ratio im thinking im gonna have to run like a 9 inch pitch to get the rpms up where they need to be but what is the speed going to be like? should i just drop a couple more pitch and see what happens? i hate to have 4 props floating around that i can not use but 9 just sounds crazy to me.
thanks
any info would be appreciated, or comments, anything really.
i just ordered and recieved a used lower unit for my 1979 mercury 50hp outboard. it is a different gear ratio than the original that came on my motor.
when i turn the new lower unit input shaft it takes aprox. 1.65 rotations to turn the prop once. on the original lower unit it is almost exactly 2 rotations of the input shaft to turn the prop once.
with a 14 pitch prop on the original i could run close to 30mph, as in GPS would say 29 then 30 and back and forth with 2 people onboard my 16ft flat bottom at 5500 to 5600 rpms.
i ordered a new prop for the new lower unit and i ordered a 15 pitch to drop rpms alittle, well this was before i realized i had a different gear ratio. it will push the boat at 18mph at 3800 rpms with just myself onboard. i was thinking the new prop was a different design or something and ordered a 13pitch prop it will run about 23mph at 4300 rpms.
with my new lower unit and gear ratio im thinking im gonna have to run like a 9 inch pitch to get the rpms up where they need to be but what is the speed going to be like? should i just drop a couple more pitch and see what happens? i hate to have 4 props floating around that i can not use but 9 just sounds crazy to me.
thanks
any info would be appreciated, or comments, anything really.