bobby allen
New Member
I have a 2015 z7 with 2021 mercury 175 4 stroke outboard trying to figure out what prop to run
Bobby, 1st let me say that based on the numbers you just gave that your setup is all wrong, you have a rigging problem or a problem in the motor itself. You should be running at least 5800 rpms at WOT. 5200 RPMs with a 21P prop on a 175 4 stroke on that hull tells me something is wrong. You may have the motor buried on the transom. Your not getting WOT which is a common rigging problem with 4 strokes (check the high and low stops if you have a hotfoot). Could be an actual problem with the motor. I have personally never owned a 150/175 4 stroke BUT from my experiences with the new larger 4 strokes is they have at or near the same rev limiter and LOTS more torque due to higher displacement. Having much more torque allows you to turn a larger wheel--not the opposite. If you can only get 5200 RPMS out of a 21p prop what makes you think a 22p prop would be better?? Another thing people don't realize is not all props have the same diameter. Props for bass boats will typically vary from 13 3/4 to 15 1/2 inches +-. This will allow a higher pitch with a lower diameter prop and visa versa with a larger diameter prop.For a two stroke outboard engine 24 or 25 pitch prop will work but I have a 4 stroke outboard engine, what I can figure out that a 22 pitch prop should work. I am running a 21 pitch prop and top rpm's is 5200 and about 55 miles hours
Update lower the jack plate down one hole and I can get 5500 rpm's, got to work on figuring out the rest of setupBobby, 1st let me say that based on the numbers you just gave that your setup is all wrong, you have a rigging problem or a problem in the motor itself. You should be running at least 5800 rpms at WOT. 5200 RPMs with a 21P prop on a 175 4 stroke on that hull tells me something is wrong. You may have the motor buried on the transom. Your not getting WOT which is a common rigging problem with 4 strokes (check the high and low stops if you have a hotfoot). Could be an actual problem with the motor. I have personally never owned a 150/175 4 stroke BUT from my experiences with the new larger 4 strokes is they have at or near the same rev limiter and LOTS more torque due to higher displacement. Having much more torque allows you to turn a larger wheel--not the opposite. If you can only get 5200 RPMS out of a 21p prop what makes you think a 22p prop would be better?? Another thing people don't realize is not all props have the same diameter. Props for bass boats will typically vary from 13 3/4 to 15 1/2 inches +-. This will allow a higher pitch with a lower diameter prop and visa versa with a larger diameter prop.
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