Prop Help

[Big D]

I’ve got a Chapparel 242 Sunest with a 8.1L & type F DPS Drive

Currently have a F8 #3851498 prop set

Running the boat at higher altitude (5,000’) and the boat is struggling on the bottom end.

Max RPM we can achieve is between 3,600-3,800

The operating range on the motor is 4,200-4,600

Need to go with a lower pitch prop set.

Any recommendations on what set I should go with to get the boat in the optimum operating range?

I’m curious if the manufacture states what the RPM increase is between each F# set?

Any feedback would be greatly appreciated.

 

[BUDMAN]

Ran F4s on my old Chaparral 252 with the 5.7. Ran great at lower rpm range. Struggled to run 50 mph. When I upgraded to F5’s it ran 50 mph no problem but tool a little longer to get on plane. For your particularly set up I would prop down to F5 or F6. As expensive as they are I would try to barrow a set to try first. Hope this helps.

 

[Fun Times]

Though it's not your engine model or year range of your setup, The following info found inside a Volvo service manual ought to help give a guidance of what to expect as you get to know your overall performance changes between prop changes.

http://boatinfo.no/lib/volvo/manuals/sx_dps-lk.html#/200 <Have a read through pages 200 (8-9) - 204 (8-12).

https://forums.iboats.com/filedata/fetch?id=7021523

 

[Big D]

Ran F4s on my old Chaparral 252 with the 5.7. Ran great at lower rpm range. Struggled to run 50 mph. When I upgraded to F5’s it ran 50 mph no problem but tool a little longer to get on plane. For your particularly set up I would prop down to F5 or F6. As expensive as they are I would try to barrow a set to try first. Hope this helps.

After consulting several experts, I went with F6's. Considerable improvement in all around performance. MAX RPM was 4,400 = 48 MPH with 2 adults & a full tank of fuel. I'd like a little more bottom end so I'm swapping them out for F5's. Lake has a 35 MPH speed limit and boat will rarely see 30+ MPH. Hoping that will give us a little more bottom end for skiing, waterboarding & hauling 10+ people around the lake.

 

[BUDMAN]

After consulting several experts, I went with F6's. Considerable improvement in all around performance. MAX RPM was 4,400 = 48 MPH with 2 adults & a full tank of fuel. I'd like a little more bottom end so I'm swapping them out for F5's. Lake has a 35 MPH speed limit and boat will rarely see 30+ MPH. Hoping that will give us a little more bottom end for skiing, waterboarding & hauling 10+ people around the lake.

If your not worried about top end speed I would run F4s. Great for wake boarding, sking, or tubing. Hope any of this helps.