Prop Suggestion Needed Volvo Penta SX Drive

[ejnichol]

Hello,
1) Looking to purchase a backup prop. Original I just sent out to correct nicks, small dent and bent blade. Slowly back into wall with trailer, bent blade, straightening cracked it.
2) Current prop manufacturer Looks to be Volvo Penta Alum 4 blade. Not sure who made it actually. Says H7 412 on hub.
3) Current prop is 4 blade diameter and pitch 14.25 X 19
4) 5,000 rpm and it may have gone higher but not being sure tach was dead on and not wanting to blow motor thats what I read or real close to before dropping throttle back to 4800 aporox., 43.5 mph on phone gps. Factory Speedo inoperative. rpm is from factory tach. Didn't have handheld test tach with me at time to verify.
5) Volvo SX, Engine 5.0 GXI 270 HP probably 300 ft/lb torque 2007 model 95 hrs.
6) Chaparral 220(22ft), 2007 3650 lbs. two people on board, 50 - 75 gallons fuel.

Looking to a 3 blade AL, that would bring rpm down to say 4800 rpm max at Full throttle.

Appreciate you time in reviewing and suggesting a decent back up prop. Boat would benefit from a dual prop setup as it kind of portly in acceleration and handling.

 

[dan02gt]

I have a 2014 Chaparral 226 SSI with the Volvo V8-270 and SX-A drive. Dry weight on my boat is 3900lbs. My opinion is pick up a good SS prop and use your aluminum prop as a backup. My runs 45MPH gps with a 17P Powertech SFS4 at 4700 RPMs and 47MPH with a 17P Powertech SFS3 at 4900 RPMs. That’s with 2 adults, 2 kids, and 50 gallons of fuel. My hole shot and acceleration are great with both props. The 3 blade is faster but the 4 blade offers better hole shot and around the dock handling. My outdrive is the 1.60. Of the 2 I prefer a the 4 blade.

 

[ejnichol]

Dan what diameters are your props the 17pitch dia ? Thanks

 

[dan02gt]

They are both 14.5"

 

[ejnichol]

Dan, Are those rpm and speed # at full throw throttle?

 

[dan02gt]

Yes they are. RPMs are coming directly from the computer via NMEA 2000 network. If your tach is the analog style it could easily be off.
If you don't have it yet get the Mercury Prop Slip Calculator. It can give you lots of good information.
For instance when I run your numbers of 43.5MPH at 4800RPMs (assuming you have the 1.6 ratio drive like I do) I come up with 19.4% slip. That's is horrible. You should be at less than 10%. So either your prop is slipping really bad or you are not turning near the RPMs your tach is saying.
When I punch in your top speed and run the calculations assuming 9% slip I come up with 4250 RPMs to achieve that speed. That sounds more believable for me and would mean your tach is off. If would also mean you can easily drop down in pitch to get better holeshot and acceleration.

 

[ejnichol]

I agree my data indicates poor hookup and or false tach reading. I found a good deal on a new oem volvo prop 14.8 X 17 3 blade alum. Will use my shop tach and phone gps to see what really going on. Once my 14.25 * 19 comes back from remanufacturer I may just sell it and get a nice 4 blade SS Prop like your running and keep this new al one as spare.