21' Scarab Prop Selection
#11
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Thread Starter
Checkmate,
Not knowing anything about your hull, and just going buy weight, I’m betting you’ll bury the rev limiter with a B28.
Keep your eye out. A B28 just popped up and sold here on OSO. Post in the “Wanted” section you’re looking for one. You might be surprised.
One more thing…. I hope you upgraded the outdrive….
Thanks. Brad.
(937)545-8991
Not knowing anything about your hull, and just going buy weight, I’m betting you’ll bury the rev limiter with a B28.
Keep your eye out. A B28 just popped up and sold here on OSO. Post in the “Wanted” section you’re looking for one. You might be surprised.
One more thing…. I hope you upgraded the outdrive….
Thanks. Brad.
(937)545-8991
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Gimme Fuel (03-24-2023)
#12
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Thread Starter
SB,
I had a B26 on our PQ while the injectors were giving us fits. After getting them straightened out, we took the boat to the lake to test them out. I couldn't get much above 2/3, maybe 3/4 throttle without bumping the rev limiter. When I reacquired a B28, I can now bury the fun stick and the engine loads out right at 5K RPM.
I'd much rather not be able to use the top end of the throttle range because my knuckles can't get any whiter, rather than because I'm afraid of a rod through the side of the block. Just sayin'...
I didn't catch that the OP had upgraded to a Bravo drive. I thought he was still running the Alpha. All good.
Thanks. Brad.
(937)545-8991
I had a B26 on our PQ while the injectors were giving us fits. After getting them straightened out, we took the boat to the lake to test them out. I couldn't get much above 2/3, maybe 3/4 throttle without bumping the rev limiter. When I reacquired a B28, I can now bury the fun stick and the engine loads out right at 5K RPM.
I'd much rather not be able to use the top end of the throttle range because my knuckles can't get any whiter, rather than because I'm afraid of a rod through the side of the block. Just sayin'...
I didn't catch that the OP had upgraded to a Bravo drive. I thought he was still running the Alpha. All good.
Thanks. Brad.
(937)545-8991
#13
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Yup. Creeping up on it is definitely a wise approach. There are those who might suggest you've got more HP than the hull can handle. I call BS on that. I grew up on a 21' Nordic daycruiser with a 482/6-71/V-drive that my dad affectionately call the "Homesick Angle". It would easily plane off at 2200RPM and could maintain plane at 1900. At 6200 RPM, we were tickling 85MPH and running about as dry as a boat has any right to. Your numbers are going to be different, but I think you're gonna be in that same realm. It's gonna be a hoot. You built all those HP. Now ya gotta load 'em up. I'm betting you're going to spin a B28 like it ain't even in the water. Curious to see how it goes and where you end up.
Thanks. Brad.
(937)545-8991
#14
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Thread Starter
Checkmate,
Yup. Creeping up on it is definitely a wise approach. There are those who might suggest you've got more HP than the hull can handle. I call BS on that. I grew up on a 21' Nordic daycruiser with a 482/6-71/V-drive that my dad affectionately call the "Homesick Angle". It would easily plane off at 2200RPM and could maintain plane at 1900. At 6200 RPM, we were tickling 85MPH and running about as dry as a boat has any right to. Your numbers are going to be different, but I think you're gonna be in that same realm. It's gonna be a hoot. You built all those HP. Now ya gotta load 'em up. I'm betting you're going to spin a B28 like it ain't even in the water. Curious to see how it goes and where you end up.
Thanks. Brad.
(937)545-8991
Yup. Creeping up on it is definitely a wise approach. There are those who might suggest you've got more HP than the hull can handle. I call BS on that. I grew up on a 21' Nordic daycruiser with a 482/6-71/V-drive that my dad affectionately call the "Homesick Angle". It would easily plane off at 2200RPM and could maintain plane at 1900. At 6200 RPM, we were tickling 85MPH and running about as dry as a boat has any right to. Your numbers are going to be different, but I think you're gonna be in that same realm. It's gonna be a hoot. You built all those HP. Now ya gotta load 'em up. I'm betting you're going to spin a B28 like it ain't even in the water. Curious to see how it goes and where you end up.
Thanks. Brad.
(937)545-8991
#15
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iTrader: (1)
Doubtful. Most likely your drive is deep in the water. Most small boats with Alfalfa’s where. This is assuming you didn’t raise drive height when you installed Bravo. Or did you ?
#16
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Thread Starter
Correct, didn't change the height at all, x dimension should be the same. Lower unit has low water pickup, not dual side, but I heard it's the same aside from that change. I should stick to 4 blade?
#17
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iTrader: (1)
5 blade is typically for high x dimension when a 4 blade is not grabbing enough water and slipping. Small performance boats don't usually need a lot of blade area. Many run 3 blades also.
Last edited by SB; 03-23-2023 at 06:03 PM.
#18
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This....
On our Rinker 236 we had before the PQ280, we bought it with a 22P 4B of some unknown make that had been reworked to 21P. The boat rode really wet, and maxed out at about 51MPH. We switched to a 23P 3B of an unknown make (it was an even "try it, keep it if you like it" swap) and the boat came alive. It rode on it ass like it was supposed to and topped out at 60MPH even.
You might try a Mirage Plus 27 or 29P. I'm still betting you'll be over 30P before the engine is happy.
Thanks. Brad.
(937)545-8991
#19
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Thread Starter
Spot on, props to you both for chiming in - a few market places have a testing period that I'll take advantage of. Starting with a 28 4 blade and potentially moving to a 30 or 32 as needed. Maybe in the future my curiosity will get the best of me and mess with a 5 blade to see what happens for ****s and giggles
#20
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Checkmate,
It's a solid hob, but it is a cheap test for a 3B prop.
Mercury Marine Mirage Plus 48-821720 a50 29p | eBay
Thanks. Brad.
(937)545-8991
It's a solid hob, but it is a cheap test for a 3B prop.
Mercury Marine Mirage Plus 48-821720 a50 29p | eBay
Thanks. Brad.
(937)545-8991