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Old 11-12-2007, 08:20 PM   #1
Lt. JG
 
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Default spun prop

I have an 05 2400 w/5ltr Merc. It usually starts to plane at about 16mph and cruz at 19/20 at 3500 rpm's. Yesterday went out and at 3500 she wouldn't go over 16. Throttled up to 4000 and the bow would come down, but if I tried to run at 3500 it just wouldn't have it. I checked the prop and it looks ok, no dings or dents. I saw on a fishing forum someone mentioned they had "spun a prop and had to limp in". I am wondering what that means and if maybe that is what has happened.
Also, I am wondering in which direction to change the prop to get better gas mileage and what do I lose by doing it?
Thanks for your help guys.
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Old 11-12-2007, 09:30 PM   #2
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well...it pretty much sounds like what your describing....in the middle of the prop is a rubber bushing that is compressed when you tighten the nut down...well...sometimes that rubber just goes out and you can get it rebushed with a new inner rubber snubber....but...sometimes it just doesn't work out and a new prop is in order....what I'd do is take it of...then over to a reputable prop shop....they will basically give it a tune up and rebush it for under a hundred bucks...then but if your going to reprop....remember that a 1 inch change in pitch will change the rpms by about 400 rpms....so...if your wot is 4400 rpm (check your manual for proper rpm range)...and you have a 19" pitched prop...then change it to say a 20"...it will lower the rpm to 4k rpm...that will probably be at the low end of the range..thus lugging the engine....lugging a boat engine is not good....a change like that will also change your hole shot or time to plane....make it longer.....if you go to a shorter pitch..you get better hole shot but your rpm will change accordingly....from say 4400 rpm to say 4800 rpm...this may put you at the high end of the rpm range...and your top end will be slightly lower...so..it's a fine balance of economy/time to plane/top end....I'd start with what you have...find your WOT (wide open throttle speed)and go from there....just my 2 braincells firing off...
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Old 11-12-2007, 11:21 PM   #3
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Thanks for your reply. I will pull it off and have it checked.
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Old 11-13-2007, 02:14 AM   #4
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Just curious, is there a way to check it before pulling it off and what size is the prop nut?
Thanks
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Old 11-19-2007, 04:25 AM   #5
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Ok so I took the prop off and down to Hipp Marine. Parts man said it didn't "look" bad but it's hard to tell. SO I bought a new hub, $20, and installed it. Went out today and WOW what a difference!
Before I would cruise at 19 mph @ 36/3700 rpm's and burn a half tank of fuel in less then 20 miles. Now at about 4000 rpm's I cruise at an easy 32-33 mph and only used maybe a quater tank.
It most of been bad since I bought it last dec.
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Old 11-20-2007, 12:16 AM   #6
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Cal...that tells me you had a spun hub....so replacing it basically fixed the prop...good news....thanks for posting!!.
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