prop help 350 with aplha
05-30-2012 | 06:14 AM
#11
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Joined: Feb 2012
Posts: 4,031
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From: westville, NJ
no engine can spend all day at wide open throttle. 3500 is running at just over half throttle, not lugging. if he put a 21 or 23 on it so it would only DO 3500, then yes he is damaging his engine.
05-30-2012 | 06:45 AM
#12
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Joined: Jul 2007
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I think your over-propped. That might not be just pitch, the Mirage is a fairly large diameter prop I believe, lots of blade area. If you're near a prop shop, that would be the ideal way to test others out. Given the numbers you posted, It would appear a Laser II might be a better choice.
I believe you engine wants to be at or near 5,000 rpm. I have a 5.0 MPI that turned 5,100 with an 21" aluminum 3 blade, and almost gets to 4800 with a 21" Laser II SS. Slippage and hole shot improved remarkably, top end a tiny bit less. I'm looking for the prop that gets me back up to 5,000. Be better for performance and the engine all around. I think a 19" would get me past the rev limiter, maybe not.
How heavy is that 24?
I believe you engine wants to be at or near 5,000 rpm. I have a 5.0 MPI that turned 5,100 with an 21" aluminum 3 blade, and almost gets to 4800 with a 21" Laser II SS. Slippage and hole shot improved remarkably, top end a tiny bit less. I'm looking for the prop that gets me back up to 5,000. Be better for performance and the engine all around. I think a 19" would get me past the rev limiter, maybe not.
How heavy is that 24?
05-30-2012 | 10:43 PM
#13
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Joined: Apr 2010
Posts: 897
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From: Daniels, WV
You originally posted this, making it sound like he needs to prop for 3500 RPM at WOT:
I added this to the mix:
Quote:
Originally Posted by 87MagnumII
3500 would be lugging the engine and cause more damage. That thing can spin to 4800-5000 all day long assuming it is in good running order
Then you come back with this:
Your posts are very confusing. The topic of conversation is WOT RPM, not cruise rpm. We all know you can't run the **** out of one all day every day. In your original post it sounded like you were suggesting a huge prop to keep rpms down and save gas, which would not be a true statement. Try to clarify your posts some.
Quote:
Originally Posted by 87MagnumII
3500 would be lugging the engine and cause more damage. That thing can spin to 4800-5000 all day long assuming it is in good running order
Then you come back with this:
Your posts are very confusing. The topic of conversation is WOT RPM, not cruise rpm. We all know you can't run the **** out of one all day every day. In your original post it sounded like you were suggesting a huge prop to keep rpms down and save gas, which would not be a true statement. Try to clarify your posts some.
05-31-2012 | 05:39 AM
#14
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Joined: Feb 2012
Posts: 4,031
Likes: 10
From: westville, NJ
are you sure that is a 350 mag? sounds more like a 260 merc. the thing with WOT rpm ratings is it shows how hard the engine is working at ALL engine speeds. they say 4400 to 4800 top rpm. you are already below the center of that number. 2 inch longer pitch is over 10% more at 17 inches pitch you have now. will put your WOT around 4000 at best. means engine is lugging at 2500 to 3500 where you usually are (supposed to be) running it. a 24 is not a small boat. like sprink says, you are right there with your set-up. you try to make it do more you are gonna hurt it.
