Boats For Sale:
What’s The Difference? |
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duffnit 
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Joined: October-12-2005 Location: United States Status: Offline Points: 235 |
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 Topic: What’s The Difference?Posted: April-18-2007 at 11:21am |
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89 SN 351 1:23 trans with a 4 blade OJ XMP vs. an 86 SN 351 1:1 trans with a 3 blade Acme (I think).
WOT out the hole the 86 is 3/4 to 1 boat lenght ahead until it reaches it's top RPM @ 4600, where the 89 over comes and passes topping out at 4900 + - RPMs. My question is this.... is the hole shot difference in the prop the transmission or is it a combination of both? I thought the 4 blade would have a better whole shot that the 3, am I wrong? d  
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Danny
"no offense- but the rate at which you spread bad information is very impressive" |
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TRBenj
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Posted: April-18-2007 at 11:42am |
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Very strange. The 1.23 should provide a better holeshot. Unless it has better heads on it, Im also surprised the '89 is turning that many RPM... 4600 should be in the ballpark for both motors if equipped with stock-ish sized props.
From what Ive seen, the 3-blade acmes have great holeshot- their surface area is equal to or greater than many 4-blades. I have heard that the OJ's have a little "softer" pull, but Im surprised to hear of that much difference- especially considering the '89 has the 1.23. |
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Hollywood
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Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13511 |
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Posted: April-18-2007 at 11:52am |
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Enough of this 3 blade v 4 blade already. It's all about PITCH. The number of blades has little to do with performance.
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eric lavine
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Posted: April-18-2007 at 12:00pm |
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Remember in the 80's masterpoops used the BW 1.52:1 for a better holeshot,I believe they sacrificed top end speed but they did achieve a great hole shot with the boat, Its a give and take... more rpms= smaller props. it is like changing sprockets on your bike, there is always a sacrifice. The 1:1 will always be the ideal ratio for ski boats because of the prop speed, the 1.23 does allow you to spin a bigger prop or a 4 blade. in theory on the same identical boats you would get a better holeshot out of the 1.23 but you would lose the top end.
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"the things you own will start to own you"
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TRBenj
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Posted: April-18-2007 at 12:05pm |
Youre right- pitch, diameter, cup, blade area, and other design factors come into play and have as much effect on performance as the number of blades- especially when dealing with props from different manufacturers. However, given props that are similar in design and have equal dimensions, the 4-blade should have a little better holeshot and the 3-blade should have a little better top end. |
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Darrel
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Posted: April-18-2007 at 12:13pm |
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Tim, Are you still planning on testing multiple props this spring?
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TRBenj
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Posted: April-18-2007 at 12:20pm |
The CC and MC engineers may disagree with you- all direct drive Nautiques come with the 1.23, and MC now offers a similar 1.26 on their direct drives with the MCX (350hp) motor. Perhaps 1.25 has been found to be a good compromise on boats of this size, weight and intended use? |
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duffnit
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Posted: April-18-2007 at 2:00pm |
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All good info.
Sorry Hollywood, guess I missed the debate, but now a victim, it has my attention (lol). Tim, I know the 4900 rpms seems high. This is achieved by the current prop. The po had a 4 blade OJ legend with a 1 1/8" bore. The first summer I used the boat I always wondered why the boat only turned 4200 rpms and wouldn't push it's way through a tight turn like my last SN. After dinging the prop right before the 4th last season rather than be without the boat I purchased the XMP. 4900 + - running 47.5 + - WOT (gps). The prop was recommended by Richard at Skidim and he was right on about the difference in performance. That reminds me, anybody want to trade 4 blade OJ 1 1/8" bore for a 1" bore 3 blade. I think Richard said that prop was for a V drive. If someones interested I can find out. d |
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Danny
"no offense- but the rate at which you spread bad information is very impressive" |
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Hollywood
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Posted: April-18-2007 at 2:11pm |
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duffnit, my point was you could have a 4 blade with a 14" pitch, and a 3 blade with a 12" pitch. In this case the 3 blade would be giving you the better acceleration. Counting blades won't get you anywhere, need to know the numbers.
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Hollywood wrote: