Impeller Diameter Options

[rktman]

Sorry if this has been asked, but my 35 hp Johnson jet has the smaller 5 3/4 impeller.
Would a larger impeller help on top speed or does it matter.
It just feels like its not transferring all the power it could.
Thanks,

 

[Grease Slinger]

Surely someone else who knows more about your setup will chime in but personal experience with jumping up a impeller size really takes it out of your motor. Not saying it isn't possible but makes a world of difference. Just my personal experience with mine

 

[Lil' Blue Rude]

Pretty sure your motor has the small jet pump on it since you have the 5 3/4 they do make a 6" impeller that would fit but you won't see any gains from it. It's going to over load the motor and just slow it down. Outboard jets changed those motor over to the medium pump with a 5 7/8 impeller later on. Not sure when, and not sure which pumps better.
The impeller might be about worn out or the blades have been sharpened enough the blades are shorter and don't catch water like they use to. Or the impeller might not have been sharpened properly. Sharpening and how you sharpen makes a big difference.

 

[rktman]

Thanks. I do suspect that it has been sharpened too many times. Is there a rule of thumb measurement from the top of the casting to the fins?