KY 256ssi

Prop advice 256ssi

31 posts in this topic

Guys my 256ssi with a custom 496 putting out 650 hp. Using a high 5 with 25 pitch seems to be a bit of a dog trying to plane.  It's also putting me at 5400 rpm. Any ideas on plaining faster while lowering those rpm's? Thanks 

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You have a challenge. For improved hole-shot, you need to drop to a lower pitch. But that will increase your RPM @ WOT. So you cannot have both. Pick one or the other...

brick

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I just went through prop scenarios here this week and acquired a lot of knowledge on here and on my own in the process chasing answers. 

I think what you suggested(4 blade same pitch) is the answer for your situation.  

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In my experience, the High 5 is a solution for underpowered boats looking for best hole shot (to pull skiers, for example).  If you've built your motor, you must like speed.  A correctly matched 3 blade will give you the best top end.  Your power, with the proper prop, will provide ample hole shot even with 3 blade.

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Just curious what speed do you get with 650 hp?  What drive do you have as well?    A 4 blade would help as they have suggested.

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I missed that it was a High Five prop, which is primarily a watersports prop. I doubt it is a good choice for high speed/high horsepower applications. Also not sure what drive the OP has. 

I would contact a prop shop that deals with hi-po boats and see what they recommend. That said, every "go-fast I have ever been on was a dog out of the hole. 

brick

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Bingo brick.  A boat can NOT have the best of both conditions.  Use 2 different props. Easy enough to change. in less than 5 minutes on a Alpha.

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+1 to Mi3Sons comment about BBlades.  I used them to lab finish my Bravo 3 props and they are good.  Sounds like you must have a Bravo 1 on your 256??  The 256 is a stern heavy boat so you need to find a prop that will provide stern lift.  When BBlades did mine, they added some cup which helped with my mid-range by providing a bit more lift.  Unfortunately, selecting props sometimes requires a lot of trial & error

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Bravo xr with a single arm hydraulic steering. I found a guy that'll let me try a 4 blade 25 pitch. I'll see about a 3 also. Would I go down in pitch on the 3 to try? I'll try Brett at bblades also. 

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Ken at Propgods is also a great resource, but he is probably a little busy right now..

KR@propgods.com

 

 

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52 minutes ago, cyclops2 said:

Bingo brick.  A boat can NOT have the best of both conditions.  Use 2 different props. Easy enough to change. in less than 5 minutes on a Alpha.

I hope his 650HP is not connected to an Alpha...

brick

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40 minutes ago, brick said:

I hope his 650HP is not connected to an Alpha...

brick

Bravo XR so he's good.  Love to hear how fast he gets the 256 going!

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I've contacted Ken at propgods so hopefully he'll get back to me. Bblades has a test program but not cheap. Thanks for all the help guys. The mechanic that worked on her at Grannpappys marine said with the correct prop she should do in the 80's. He didn't know the first owner that had the engine made but the owner I bought it from said it was "way too much engine for him." He now has a pontoon. 

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Ive played with the ssi hulls, I don't seed 80 coming from them and its going to be a scary ride up over 65-70. they are wide and heavy, don't have enough dead rise or a hull pad.

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Yeah I am skeptical also. I'm really looking for better plane and get those rpm's down. Once I find the right prop I've been reading the trim tabs vs dolphin thread. Looks like tabs may be in my future.

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12 minutes ago, Mi3sons said:

Ive played with the ssi hulls, I don't seed 80 coming from them and its going to be a scary ride up over 65-70. they are wide and heavy, don't have enough dead rise or a hull pad.

I don't see it either low 70s more than likely. my 29 fever had 730 was built for that and got mid 70s.  don't see a boat roughly the same weight and hull not built for speed doing 80s.

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i know JC from this forum had 600+ HP on his 256 SSi with a Bravo 1.  He was running right around 70+.  I can't see this hull hitting 80 as it rides way too wet and doesn't have the lift to run that fast.

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40 minutes ago, MonkeySeaII said:

i know JC from this forum had 600+ HP on his 256 SSi with a Bravo 1.  He was running right around 70+.  I can't see this hull hitting 80 as it rides way too wet and doesn't have the lift to run that fast.

How do I find JC? I looked up that on members and 124 members have jc in their name. 

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jcj256 sold his boat years ago so he's not on hear anymore but you may be able to message him.  I remember he added a pro-Charger to his 496

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