Prop Question

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Jshawlatta

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I have a 2013 4 stroke 9.8 Tohatsu on a 14' jon boat. Motor came with a 7.5 pitch prop which does great with just me and my son in the boat. Turning 6000 RPM's. Problem is when I load the family, gear, and 100 pound Lab I drop down to 5300 RPM's and about half the top end speed. My question is if I go to a 6 pitch prop should it help top end and make motor run better. I have a tach so I can make sure not to exceed 6000 RPM's when I have a light load. I realize its just a 9.8 and no speed demon. I bought it because we like to camp and the lakes at state parks here require a 10hp or less. I would just like to get as much as I can out of it without damaging the motor. Thanks and great site by the way.
 
[url=https://www.tinboats.net/forum/viewtopic.php?p=328261#p328261 said:
Jshawlatta » Today, 09:03[/url]"]I have a 2013 4 stroke 9.8 Tohatsu on a 14' jon boat. Motor came with a 7.5 pitch prop which does great with just me and my son in the boat. Turning 6000 RPM's. Problem is when I load the family, gear, and 100 pound Lab I drop down to 5300 RPM's and about half the top end speed. My question is if I go to a 6 pitch prop should it help top end and make motor run better. I have a tach so I can make sure not to exceed 6000 RPM's when I have a light load. I realize its just a 9.8 and no speed demon. I bought it because we like to camp and the lakes at state parks here require a 10hp or less. I would just like to get as much as I can out of it without damaging the motor. Thanks and great site by the way.


ive been told by some that a good rule of thumb is for every inch of pitch change you gain or loose 200 rpm's. so if your 7.5 was turning 6000 rpm's and now turns 5300 going to a 6 should put you around 5600 in theory. like I said it gives you a good idea where to start if you want more or less rpm's. my opinion is with your whole crew in the boat that motor no matter what prop you put on it will not be able to get to 6000 rpm's when fully loaded. you may wanna think about a 15hp model. if 6000 is the operating range you will wear that motor out running wide open at 5300 rpm's, think of it like somebody trying to run as fast as they can but somebodys holding on to their collar making them get tired faster and that's what your motor will do. you will put more strain on it the more you use it and things will start to go bad...
 

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