triple cupped prop

[3car]

I have a 21' Sylvan aluminum boat that is a bit underpowered with a 90hp Evinrude. It had a 17p prop and was only turning 4200 at WOT. I found a 13p stainless prop on ebay new for $140, but I didn't do enough research before the purchase.
Come to find out it is a 13p triple cupped prop for pontoon and similar applications. I havent received it yet, but now i'm concerned that I just wasted my money because I'm not really getting my desired pitch.
Will this prop perform ann better than the 17p aluminum wheel that its replacing?

 

[Dhadley]

Re: triple cupped prop

"Back in the day" OMC called those props tripple cupped to desiginate them for use on pontoons. SSTs were "cupped" and the SST II was "double cupped". Today we realize there's more to it than that. If I remember correctly those props didn't have much rake. However, if you're only turning 4200, you're looking for more rpm than you're likely to get with a simple pitch change.

 

[3car]

Re: triple cupped prop

"Back in the day" OMC called those props tripple cupped to desiginate them for use on pontoons. SSTs were "cupped" and the SST II was "double cupped". Today we realize there's more to it than that. If I remember correctly those props didn't have much rake. However, if you're only turning 4200, you're looking for more rpm than you're likely to get with a simple pitch change.

Thanks for the reply.

the box in the auction said SST, and the omc part number is 175013. How will I get the additional rpm's, repower?

what should I expect from this prop?

 

[junior1113]

Re: triple cupped prop

you should pick up 400-500 rpms.

one more thing to check is setup where is cavitation plate in relation to bottom of trasom?

if we can go up and put the 13 on there it might just work. ussually if motor can go up more rpms can be achieved there also. i know where underpowered but get all you can.

what is max hp for hull?

 

[3car]

Re: triple cupped prop

you should pick up 400-500 rpms.

one more thing to check is setup where is cavitation plate in relation to bottom of trasom?

if we can go up and put the 13 on there it might just work. ussually if motor can go up more rpms can be achieved there also. i know where underpowered but get all you can.

what is max hp for hull?

max hp is 180. it planes out decent and runs about 30mph, but it just doesnt have the rpm's on the top end.

the cavitation plate is about an inch above the bottom of the hull if i remember correctly.

 

[junior1113]

Re: triple cupped prop

i would move the motor up 1 set of holes at least. at 30 mph the water is coming offthe back off that boat at a good angle. the higher the better when top speed is low. try this with the 13 and come back with new #'s