Need a 13x19 non cupped i think?

[AEROCOOK]

Hi all. I am currently running an 13.25 x 17 pitch aluminum prop on my 16' aluminum bowrider, the motor is a 1988 Johnson 110 hp.
The WOT RPM is 6100 and it gets there fast, which is just a little bit high from what I have read in this forum. I wanted to bring the RPM down to around 5800 so I tried a 13.25 x 19 prop but it brought the RPMS way down to 5400. I did a little more research and determined that my 17 pitch prop is not cupped and the 19 pitch prop is cupped. My theory and please correct me if Im wrong, is to find a non cupped 19 pitch prop and that will hopefully put me at or about 5800 RPM at WOT.
If you think this is logical, it brings up another question... When buying a prop "unseen" i.e. online, how would you know if it has a cupped design on non cupped design? The adds that I have looked at online dont seem to include this detail in the product description.

 

[steelespike]

Re: Need a 13x19 non cupped i think?

I would say you need a 17 cupped. A cupped prop has a better grip on the water will resist venting and allow a higher mount position on the motor.You might also consider a 4 blade like the Solas Amita in a 17.It will improve hole shot,stay on plane with less power,resist venting,run smoother,have better control at the dock and allow higher motor mount and trim.It will also likely lower your max rpm a couple of hundred.

 

[AEROCOOK]

Re: Need a 13x19 non cupped i think?

I would say you need a 17 cupped. A cupped prop has a better grip on the water will resist venting and allow a higher mount position on the motor.You might also consider a 4 blade like the Solas Amita in a 17.It will improve hole shot,stay on plane with less power,resist venting,run smoother,have better control at the dock and allow higher motor mount and trim.It will also likely lower your max rpm a couple of hundred.

Thanks for the advice, I wondered what was the more logical way to go i.e. cupped 17 or non cupped 19 and it sounds like there are more advantages to the cupped 17.
As for my question about purchasing online, how can you tell what you are getting?

 

[kenmyfam]

Re: Need a 13x19 non cupped i think?

If you have the 19" cupped and are not going to return it you can always machine the "cup" or as much of it as you want to off it. I did that when I was fine tuning my bigger "cupped" prop. It is now almost cupless !!!
Just have to be careful that you keep it even on all blades so it stays in balance. I fine tuned mine with a surface grinder wheel balancer and a mandrel.
Good Luck.

 

[AEROCOOK]

Re: Need a 13x19 non cupped i think?

If you have the 19" cupped and are not going to return it you can always machine the "cup" or as much of it as you want to off it. I did that when I was fine tuning my bigger "cupped" prop. It is now almost cupless !!!
Just have to be careful that you keep it even on all blades so it stays in balance. I fine tuned mine with a surface grinder wheel balancer and a mandrel.
Good Luck.

Thanks, the prop is not new, it was on the motor when I bought it, the motor was originally on a bigger and heavier boat than mine, so I guess the previous owner was clueless as it relates to prop selection, if it cant reach 5500 RPM on my boat it must have been a lot less on the other boat. Since I dont have the specialized tools to modify the prop I will just replace it with what I need. Ideally I want to buy a used one but then I cant return it if it doesnt meet expectations so I will likely buy new.

 

[steelespike]

Re: Need a 13x19 non cupped i think?

Thanks for the advice, I wondered what was the more logical way to go i.e. cupped 17 or non cupped 19 and it sounds like there are more advantages to the cupped 17.
As for my question about purchasing online, how can you tell what you are getting?

I don't know if you can tell unless you talk to a factory representitive.or email on there website.The description of a specific brand/model might give a clue,but the very few i've read seem to be kind of vague. From what I've seen the Solas Amita 4 blade has been very predictable and quite reasonable.