Best props for Scarab 38
10-05-2015, 07:40 AM
#1
Best props for Scarab 38
Hi,
I wonder what props would be best for my boat:
I have a Scarab 38 Thunder (1993, non-stepped kevlar hull). The boat has Mercury 496 Magnum HO engines and Bravo 1 drives.
I currently run 26-inch Bravo 4-blade props, but this combination does seem a bit heavy, as I suspect the engines don't see full rpm numbers at full throttle.
I talked to a guy with a similar boat/Engine/outdrive combination. He put 25 inch Rev 4 props on his boat, and was really pleased with the result, but I want to know if there's anyone else out there with experience from a similar boat/prop combination...
Best regards,
Lukas
Öckerö, Sweden
I wonder what props would be best for my boat:
I have a Scarab 38 Thunder (1993, non-stepped kevlar hull). The boat has Mercury 496 Magnum HO engines and Bravo 1 drives.
I currently run 26-inch Bravo 4-blade props, but this combination does seem a bit heavy, as I suspect the engines don't see full rpm numbers at full throttle.
I talked to a guy with a similar boat/Engine/outdrive combination. He put 25 inch Rev 4 props on his boat, and was really pleased with the result, but I want to know if there's anyone else out there with experience from a similar boat/prop combination...
Best regards,
Lukas
Öckerö, Sweden
10-05-2015, 03:33 PM
#2
Platinum Member
Platinum Member
Did you change the X dimension ? If not the drives are mounted very deep on that hull you might be better off with a 3 blade Mirage plus 25 Pitch that boat came with 23p mirage props from Wellcraft with 502 EFIs
10-06-2015, 12:38 PM
#3
The X-dimension was never changed, but I have been thinking about whether I should raise it, as I will replace the wood in the transom in the near future. Any recommendations on this (X-dimension) would be appreciated as well!
(Should I plan ahead as to what propellers would be good if the X-dimension is raised, or would it be too much of a difference, making it better to wait, and change propellers when the X-dimension is changed?)
(I also noted that the outer halves of the anti-ventilation plates will go in the water coming from the transom att planing speeds, which seems to indicate that the drives are mounted low down...)
You are right about the original Engines: There were a number of options, but at least I know this particular one had the 502 Magnum engines before the last engine swap, with an output of 425 crankshaft HP. As these were replaced with brand new 496 HO Engines (425 propshaft HP) engines, propellers were changed from Bravo 24p to Bravo 4b 26p. They seem to have reasoned that the boat needed bigger propellers as there is more power in the 496 engines.
The boat has "38SC" stamped in underneath the HIN number. Could this be indicating that it originally came with Super Charged engines? (There were two supercharged engine options that year...)
The lettering "38SC" underneath the HIN number is also followed by a third row with the lettering: "C. A. L." Does anyone know what that means?
A similar boat tested in Powerboat Magazine in 1992 had 465 hp engines and was outfitted with 14, 5/8" x 23" Mirage propellers, so I think you're right about the original propellers. Does that mean that I could even use 23p Mirages instead of the suggested 25p Mirages?
The test boat had 465 engines (445 propshaft HP), making it close to my 425 propshaft hp engines...
Also, any input on characteristics for Mirage 3b props vs Bravo 4b and Revolution 4b props would be greatly appreciated!
(I know 4b props have better grip in general, but what about top speeds, cruising speeds, bow/stern lift, and other characteristics?)
Thanking you in advance!
(Should I plan ahead as to what propellers would be good if the X-dimension is raised, or would it be too much of a difference, making it better to wait, and change propellers when the X-dimension is changed?)
(I also noted that the outer halves of the anti-ventilation plates will go in the water coming from the transom att planing speeds, which seems to indicate that the drives are mounted low down...)
You are right about the original Engines: There were a number of options, but at least I know this particular one had the 502 Magnum engines before the last engine swap, with an output of 425 crankshaft HP. As these were replaced with brand new 496 HO Engines (425 propshaft HP) engines, propellers were changed from Bravo 24p to Bravo 4b 26p. They seem to have reasoned that the boat needed bigger propellers as there is more power in the 496 engines.
The boat has "38SC" stamped in underneath the HIN number. Could this be indicating that it originally came with Super Charged engines? (There were two supercharged engine options that year...)
The lettering "38SC" underneath the HIN number is also followed by a third row with the lettering: "C. A. L." Does anyone know what that means?
A similar boat tested in Powerboat Magazine in 1992 had 465 hp engines and was outfitted with 14, 5/8" x 23" Mirage propellers, so I think you're right about the original propellers. Does that mean that I could even use 23p Mirages instead of the suggested 25p Mirages?
The test boat had 465 engines (445 propshaft HP), making it close to my 425 propshaft hp engines...
Also, any input on characteristics for Mirage 3b props vs Bravo 4b and Revolution 4b props would be greatly appreciated!
(I know 4b props have better grip in general, but what about top speeds, cruising speeds, bow/stern lift, and other characteristics?)
Thanking you in advance!
Last edited by Scarab Viking; 10-06-2015 at 01:04 PM.
10-06-2015, 01:42 PM
#4
Platinum Member
Platinum Member
The original 502 mag was only 415 HP. When delivered that boat came with 23 Mirages as deep as those drives are your best bet would be to change to a 2 or 3 inch shorty drive lower from IMCO that way you don't have to raise the motors in the boat then you can get away with running a 4 or 5 blade prop
10-07-2015, 12:51 PM
#5
OK, thank you. Imco lowers would be nice, but they are no cheap solution, as they will cost around 13 grand where I live, including shipping and taxes...
What about extension boxes? Are the drives raised as well when you mount extension boxes, or do you have to adjust this too, making it necessary to replace the lower units to make the extension boxes worth using at all?
If the drives stay at the same height when mounting extension boxes then it could be worth raising the engines after all, when replacing the wood in the transom, right ?
(Boxes are only half price of shorties, and they also include hydraulic steering... I wish I had an unlimited boating budget...)
What about extension boxes? Are the drives raised as well when you mount extension boxes, or do you have to adjust this too, making it necessary to replace the lower units to make the extension boxes worth using at all?
If the drives stay at the same height when mounting extension boxes then it could be worth raising the engines after all, when replacing the wood in the transom, right ?
(Boxes are only half price of shorties, and they also include hydraulic steering... I wish I had an unlimited boating budget...)
11-21-2015, 05:33 PM
#6
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Location: Philadelphia, Pa
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Running 25 mir. + s with 540s around 640 hp at 5300. 9500 lbs , 75 mph. TRS drives and 7 clutch 71c trans. Props turn out . 27p boat goes 83 mph. Rpm 4700.
