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Correct prop vs optimum rpm's |
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rithmetic man 
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Joined: January-23-2009 Location: United States Status: Offline Points: 168 |
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 Topic: Correct prop vs optimum rpm'sPosted: April-08-2010 at 9:16pm |
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I have just recently changed my prop to a 13 x 11 and have gained an appreciable difference in hole shot. My WOT will max out at about 5200 to 5300. The motor is a 302. Is this acceptable or should I stay below 5000 rpm?
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"Life is hard; It's harder if you're stupid...Pilgrim..."
John Wayne 1965 Nautique |
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8122pbrainard
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Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Posted: April-08-2010 at 10:02pm |
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Wayne,
How did you end up with the 11 pitch? I hope you got it used because it's really too low a pitch. We were all suggesting 13 x 12's or 12 x 13's. I wouldn't take that engine past 4400 or maybe 4500. You can run the boat this way (I seem to remember you did need the hole shot.  ) but keep the RPM's down. No WOT barefoot runs!!
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Luchog
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Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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Posted: April-08-2010 at 10:04pm |
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I'd say stay below 4500 if you have a stock motor, though it could spin 4800 easily all day long.
What do you use your boat for? |
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YooperSully
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Joined: August-07-2009 Location: Hancock,MI Status: Offline Points: 316 |
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Posted: April-08-2010 at 11:04pm |
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<<< was going to buy a 10.5x13
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87' 2001
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Luchog
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Posted: April-08-2010 at 11:48pm |
do you mean 13x10.5? that would be a prop for HEAVY duty wakeboarding, what boat and how much weight on it? |
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JoeinNY
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Posted: April-09-2010 at 2:09am |
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Its a little fast to be spinning a stock engine.. but if you need the whole shot just be easy on the throttle. It does seem you could use a little more prop and still have a good hole shot while also saving a little gas and gaining a bit of top speed, but if hole shot you want just enjoy it and pull back when she starts heading north of 4900 or so.
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YooperSully
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Posted: April-09-2010 at 3:13am |
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Yeah that's what I meant. I run around 900 liquid ballast and between 600 and 1000 in human weight on average.
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87' 2001
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GottaSki
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Joined: April-21-2005 Location: NE CT Status: Offline Points: 3363 |
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Posted: April-09-2010 at 11:26am |
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I concur with Joe
A stock 302 bottom end is typically good for 6000, and he's still quite below that. If he had the 351, the rod speds are higher, and he would be too close to its 5500 breakover point. |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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rithmetic man
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Posted: April-09-2010 at 2:50pm |
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The reconditioned 13 x 11 was too good a deal to pass on at the time just to try. It surely does provide a great hole shot but the rpm's are more than I need. It was exciting for a couple of minutes, the gray hair found a little color. At least I have a good drop down point now.
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"Life is hard; It's harder if you're stupid...Pilgrim..."
John Wayne 1965 Nautique |
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james1203
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Joined: February-05-2010 Location: Cairns Status: Offline Points: 10 |
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Posted: April-13-2010 at 7:18am |
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Hey guys,
I have a 98 Ski Nautique, 351 Ford engine with the PCM 40A gearbox. I am doing alot of wakeboarding/kneeboarding but I have the standard 4 blade fitted at the moment. The guys I go with have real trouble trying to keep the right speed as the boat just wants to plane out at around 25-28km/h then it jumps to 35-38km/h. We like to be boarding at the 30km/h make. Has anyone got a prop recommendation? I have been told to buy ACME. thats was great, however, way too meny to choose from. i dont want to waste my money on a new prop if it's not going to help. all help is much appreceiated Regards James |
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GottaSki
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Posted: April-13-2010 at 11:26am |
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James I think your hommes need to work on their driving skills.
Please excuse if obvious, but worth explaining first. Driving is hands-on, full situational awareness affair; Brace the right side of the palm against the boat and flex the thumb, index and middle fingers to move the throttle in precise movements. If they are doing the freehand wrist - flex for throttling, you're at a disadvantage no matter what prop you choose. |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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TRBenj
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Posted: April-13-2010 at 11:35am |
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I agree with Gottaski. The driver's right elbow should be resting on the gunnel to aide in precise throttle control. Inboards in general- and especially Ski Nautiques- are by far the easiest types of boats to hold speed with.
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james1203
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Posted: April-14-2010 at 8:31am |
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Hey guys,
Thanks for the tips on driving. I'm not sure how they do it as I am behind the boat when they drive. but will pass it on. I also have a 270 ltr ballast tank under the rear seat which obiviously make the back end drop in the water and hole shot is not that great. I thought of getting a different prop with better hole shot, inturn higher revs and then better control over boat speed. does this sound right or am I way off????? |
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YooperSully wrote: