Prop slip issues on my Scarab 29 HP 500
02-16-2015, 05:26 PM
#41
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Griff,
i'm not sure what you're saying, a pantera with what power? every hull is different and every setup is different. the point I was trying to make is that a boat setup to run 65 or 70 probably should not have a nosecone. under 80 mph the nosecone is just adding drag in most cases. higher x-dim boats/ bigger hp/ faster, can realize the potential of a nosecone.
-m
i'm not sure what you're saying, a pantera with what power? every hull is different and every setup is different. the point I was trying to make is that a boat setup to run 65 or 70 probably should not have a nosecone. under 80 mph the nosecone is just adding drag in most cases. higher x-dim boats/ bigger hp/ faster, can realize the potential of a nosecone.
-m
02-17-2015, 01:14 AM
#42
Charter Member # 55
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Mine was a 66-67mph boat with a single 525SC. My point was that I doubt that removing the nosecone will make any significant difference.
It was a 63mph boat with 25% slip when I got it. After some prop tweaking and increasing the drive spacer by 1", the slip was down to around 17%
It was a 63mph boat with 25% slip when I got it. After some prop tweaking and increasing the drive spacer by 1", the slip was down to around 17%
02-17-2015, 09:19 PM
#43
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gun slinger,,
do you know what your propshaft height is? i'm Very Interested if you care to share,,,,,,,
do you know what your propshaft height is? i'm Very Interested if you care to share,,,,,,,
Im running a 29 with twin custom 427 big power small tblocks, pushing way into the upper 90's low low hundreds with 32's It's not so much just power that you need with this boat, its matching Torque. Seems like you have a good motor to start with, needs big heads, big cam, maybe a huffer on top if you want to get into the high 70's-80's. Keep in mind it would be wise to forge out the bottom end as well for extra security.
Another option per Larry Smith is to change the X dimension with a box and play with the length of your bottom end of the drive. What people are saying is correct, its a heavy boat for a single, you need to get the ass end up out and on top of the water.
Another option per Larry Smith is to change the X dimension with a box and play with the length of your bottom end of the drive. What people are saying is correct, its a heavy boat for a single, you need to get the ass end up out and on top of the water.
02-17-2015, 09:22 PM
#44
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do you know your prop shaft centerline height?
I had the same issue on my 27 Donzi 27 ZR. Believe it or not, a spacer solved the problem. Installed a new 525 and the boat ran 73 (about 26% prop slip). I added a one inch spacer and got no real difference in performance. After the 1 in spacer and 28 p four blade, I tried a 5 blade. Because of hitting the rev limiter, I went with a 29p which should have and did knock the rpm's down 500. That solved the rpm problem, but the performance was the same. I only got 73 on gps. Hole shot wasn't any better and cruise about 42 mph on gps.
Next step was to change the spacer to a two inch. That solved a lot of problems for me. I started with the 28p, 4 blade and got to 75 mph before running out of lake. Water was very choppy and it was a very windy day. Higher speeds were definately obtainable if I had had more room to run. Notably, the hole shot was great and cruise improved to 45.6 mph.
Next, I tried the 29p 5 blade. It was a pig getting out of the hole and still only ran about 73. A lot of that was due to the prop finally being fully submerged. I'm either going to sell it or have it worked to a 27p and use it for a back up prop.
I also ran a 27p 3 blade just to see what the extra bow lift would do. Again, only got 73 mph, but that was in part because I was too busy holding on to the boat! It was a wild ride, and I don't recommend it.
I'm very happy with the 2 inch spacer/ 28p b1 4 blade. All my test runs were in fresh water and I believe that when I get it back in the Gulf, I'll see 80 mph.
And as an added note, I had 4 adults and a child with a full tank of gas, on yet another windy, choppy day and still had good performance. Good hole shot, 45 cruise, and hit 73 mph.
All in all, a vast performance over the 496 ho where I only got to 64 at WOT with a ton of prop slip.
Next step was to change the spacer to a two inch. That solved a lot of problems for me. I started with the 28p, 4 blade and got to 75 mph before running out of lake. Water was very choppy and it was a very windy day. Higher speeds were definately obtainable if I had had more room to run. Notably, the hole shot was great and cruise improved to 45.6 mph.
Next, I tried the 29p 5 blade. It was a pig getting out of the hole and still only ran about 73. A lot of that was due to the prop finally being fully submerged. I'm either going to sell it or have it worked to a 27p and use it for a back up prop.
I also ran a 27p 3 blade just to see what the extra bow lift would do. Again, only got 73 mph, but that was in part because I was too busy holding on to the boat! It was a wild ride, and I don't recommend it.
I'm very happy with the 2 inch spacer/ 28p b1 4 blade. All my test runs were in fresh water and I believe that when I get it back in the Gulf, I'll see 80 mph.
And as an added note, I had 4 adults and a child with a full tank of gas, on yet another windy, choppy day and still had good performance. Good hole shot, 45 cruise, and hit 73 mph.
All in all, a vast performance over the 496 ho where I only got to 64 at WOT with a ton of prop slip.
02-18-2015, 07:59 AM
#45
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Mine was a 66-67mph boat with a single 525SC. My point was that I doubt that removing the nosecone will make any significant difference.
It was a 63mph boat with 25% slip when I got it. After some prop tweaking and increasing the drive spacer by 1", the slip was down to around 17%
It was a 63mph boat with 25% slip when I got it. After some prop tweaking and increasing the drive spacer by 1", the slip was down to around 17%
I agree, removing the cone might not increase speed much but it could help with turning blowout etc. which he mentioned when prop testing.
I was curious about your comment on the pantera because my magnum hull is essentially the same(but I have twins) and I have had my own issues with slip ( 4 sets of props to prove it) and also considered 1" spacers which I bought and never installed. I would have thought your setup could easily get to 12-13% slip...
02-18-2015, 12:44 PM
#46
Charter Member # 55
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My issue was the prop was not deep enough to leverage and lift the bow. It responded very little to trim and the boat ran too wet.
It was a single with a notched transom so the X was really high. From the factory it came with a 2" spacer and propshaft height was 3.25" below bottom.
Lowering it another inch with a 3" spacer made a big difference in how it carried the bow.
It was a single with a notched transom so the X was really high. From the factory it came with a 2" spacer and propshaft height was 3.25" below bottom.
Lowering it another inch with a 3" spacer made a big difference in how it carried the bow.
05-13-2015, 08:23 PM
#49
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The nosecone on the lower unit can be a problem as stated earlier. Don't need it at approx 62 mph. If your boat requires a lot of positive trim to run at speed the nosecone sticks down farther in the water than a standard case without one. Trim it when its out of the water and you'll understand. It drags further down and it may be disrupting the water flow again as previously stated. Nosecone is for roughly over 85 mph and meant more for boats that have a more natural lift. If any rig trims too much with one it will drag. I know cause it happened to me. Just a thought.
