New Props for a '99 330 Sundancer? Need help!

D

David M

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Mar 5, 2005
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16492
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I WAS going to swap my 16x16 (cup unknown) 3 blade bronze props for 16xXX Michigan Wheel DQX 4 blade NiBrAl's. WELL...The NiBrAl's come in 17" diameter minimum. Couple that with the minimum cost of an unmodified (shaving 17" to 16") off the shelf NiBrAl is close to $1000 each, then add the shaving and cupping, the cost of the NiBrAl's rises quickly to ~$1300 each. Even the prop shop owner was shocked at the price increase since 5 years ago.

That said, changing to NiBrAl's is cost prohibitive right now. My prop shop has recommended pulling the three blades , decreasing the pitch to 15" and putting a heavy cup in them to theoretically increase the pitch to 16 or 17 inches while maintaining max WOT RPM's. In addition, the mods on the existing props would increase rear flow of water over the rudders and lessening the "spew" of wasted water against the hull bottom.

The cost to do this would be roughly $350 for both props.

I am pulling Saint Max ~June 1 to have it detailed and painted. While it is out, I can do the props at the same time. I can't waste $2000 plus, but I don't want to waste $350 unnecessarily.

What are fellow RO's experience with modifying three blade props. Based on Mrs. Robinson's experience with 4 blades, I would prefer the 4 blades, but, as said, it is not a player this year.

TIA.

Any and all input welcome.
 
So you are over revving and want to reduce your WOT rpms to the max as recommended? That said, I'd either load the boat down with a whole bunch of gear or spend $350 for the cupping. I don't have any experience with the 3 to 4 blade and considered it for a while. With that kind of cost for the new NiBrAl's I'd be looking for a used set or just get the current set cupped and see how they perform.
 
quote:
Originally posted by jtsmlarson

So you are over revving and want to reduce your WOT rpms to the max as recommended? That said, I'd either load the boat down with a whole bunch of gear or spend $350 for the cupping. I don't have any experience with the 3 to 4 blade and considered it for a while. With that kind of cost for the new NiBrAl's I'd be looking for a used set or just get the current set cupped and see how they perform.

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No. I am within the Mercruiser WOT range. About 4900 to 5K on each engine fully loaded. I get about 19 to 22 knots depending on wind and tides at cruise. Friends with the same boat with 7.4's are getting 25 knot cruise. The torque curve on my 6.2's are roughly the same as a 7.4 albeit at a higher RPM. My concern is not so much speed, but optimum performance for the rig as a whole.

I have experience with the 3 to 4 blade conversion. It is huge. If the money was there, the change would be a no brainer. For the 2008 season, I need to make the best within the available budget.
 
I have 98 330 dancer with 7.4 V-drives. I have 3 bladed props 17x17 i think. Dinged props 2 years ago and they were replaced with Nibral 3 blade props. It increased overall performance by 2 knots. I now cruise at 3300-3400rpm at about 25knots.I dont know if the old props were out of "tune" but i noticed a difference with the new nibral props. good luck
 
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