Tunnel hull boat (Sterling TR7) engine is recessed in the transom with a tunnel extension that fills the void between the area you would consider sponsons sort of.
Engine is Yamaha 115 SHO on jackplate with PowerTech SWW3 prop 13” pitch. Im seeing 6000 rpm’s at WOT and 36.5 mph. Prop does good overall expect hole shot and some porpoising when trimmed out a little
My problem I’m experiencing is there is no hookup/bite from the prop during hole shot. This is when I’m utilizing some vertical travel on the jackplate and the engine trimmed all the way down. Previous engine 2 stroke Yamaha 90hp had a cav plate on it and the prop then had less cupping than the SWW3 does in running now.
My question is, a better prop with more ability for hole shot/maybe a 4 blade in the SWW4 version or a cav plate will be needed regardless to utilize the jack plate being elevated when attempting hole shot?
Thanks for the help.
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What’s your budget for this endeavor? If you can afford to spend some money on this you could get a Shaw Wing and a custom prop (Foreman, Baumann or Holeshot Performance). If you really don’t want to spend a lot but see some improvement try one of the PowerTech shelf props like the SWW line. I recommend calling them to see what prop would work best with your rig. You can probably get somewhere in between and talk to a local custom prop shop that would add cup to a shelf prop. I’m a big fan of three blades with extra cup but some guys swear by four blades.
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I’m running the SWW3 prop now. I’ve tried going with a Shaw wing the problem is the tunnel extension, sponsons, and how the engine is recessed in the hull the Shaw wing hits the tunnel extensions or sponsons. Closest I’ve found is the trans cav plate or permatrim (ehh). I attached photos of what is coming from factory but haven’t had luck in obtaining one.
I’m just battling with is it the prop, Cav plate, or both that’s causing the poor performance.
Budget wise I’m fine spending the money to get it to perform right but not dropping several thousand for a prop.
Post photos of your transom, prop and everything. It’s hard to do this remotely but I can if you give enough information and visuals.
I can tell you right now if your prop looks like that photo you just post you don’t have enough cup. You might need to go with a Tran CP100 to keep from hitting the tunnel extension.
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Photos of current prop, engine and transom, and photo of old engine and the type of Cav plate it had on the 90 2 stroke. The prop on the engine was from my 90 2 stroke that was all I had at the time of repower, now have the PowerTech SWW3.
Only let me post 1 photo at a time.
Only let me post 1 photo at a time.
Only let me post 1 photo at a time.
Only let me post 1 photo at a time.
That prop cup is weak. The SWW4 may be what you should buy to suit your budget. Add a Tran CP-100 if you want a compression plate, it will help hole shot.
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I’d agree with Mac that the cup isn’t the best there.
My experience with a 3b-4b is this. Personally I like the 4b props, they do give a better holeshot ( apples to apples) so an off the shelf, same brand prop 3b vs 4b.
However a 3b can be made to perform the same if not better.
Either way to run up on a plate you’re going to need cup, and if you can figure out a compression plate, it’ll definitely help.
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To be brutally honest, I believe the tip cup on the PT prop (pictured by itself) is wrong, and is the reason for loss of hookup on hole-shot. It’s also struggling to reach maximum recommended RPMs. The cause is the tip cup wraps too far forward around the tip toward the leading edge. It’s working against itself.
I know this because I wanted more bow-lift and had extra tip cup added the same way to a Yamaha Pro Series prop and it behaved the same as you describe. I lost grip, speed and RPMs. The prop works best without that disturbance on the leading edge where it needs to cut into the water effortlessly - if I make sense.
Don’t get me wrong, extra cup added is a good thing. Just not wrapped too far forward like it is.
This is what real custom cupping looks like.
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I assumed and based on what I had read and anyone I spoke to said the sww3 was one of the strongest cupped props on the market that isn’t custom made by someone like jack or others. Once on plane any people I have ever ran has no issues with having grip at the highest elevation possible. I can use all 6” and some trim on plane and have no negative effects. It’s the hole shot I’m struggling with the most it seems.
The rpm’s and speed I’m seeing im not upset with. The 15 pitch I had did 37-38 mph at 5800 rpm’s. It’s generally the hole shot that’s the problem. Both this and prior turning point 15 pitch I could use all 6” of jackplate and hold water. I had just heard nothing but great things on the SWW3 and was told that’s the prop I need.
It’s all a compromise. Think of propping a boat like a slide ruler with hole shot/ shallow performance on one end and speed on the other. If you slide towards hole shot your speed generally drops, slide towards speed and hole shot drops. Finding the balance of both is where you want to be.
I’m sorry I can’t just tell you what you need. If I had your boat, time to tweak how it’s set up and a couple of days to test props I could get you set up. I can’t do that. I gave you the best options now it’s up to you to take that information and make phone calls, get some props to run and figure out what works best for your goals. I have lots of people who are not my clients who contact me and want me to basically be a shallow water consultant without physically seeing their setup and getting to run it. I can usually help but sometimes my advise only goes so far.
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That’s a fair point you make on everything. I’m gonna keep on the hunt and might just bite the bullet and get a prop from jack or Baumann. In my case which prop would perform to what I’m looking for to find that balance?
Thank you again for your help.
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If I do custom would a foreman prop or baumann be about the same or does either one do better than the other at anything in particular from your experience. If you ever travel to fort Myers area please let me know also.
Thank you
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