5 blade for midrange performance?
 

I spoke w/Cutting Edge props in California about maximizing mid range performance on my 30' w/mag HO's and his recommendation was to use a 5 blade, down 1" in pitch and maybe a little tuning to get the max RPM is line. Agree...disagree.

agreed,i run 5 blades love them.little off of top end but never blow them out,also they hook up great when re-entering water!

Agreed, 5 blades are more efficient, especially noticable at cruise speed.....less rpm to maintain the same speed as 4 blades.
Everytime you add a blade, you drop a degree of pitch.
I just had Cutting Edge work my Hydromotive 5 blades with excellent results.
I have not tried their own design of props but will definately do it in future applications.

Should I go w/stock 5's for everyday and have the 4's I have now labbed for special days or go 5 labbed for everyday?

I'm thinking stock 5 blades will work, really no need to Lab them.
Having said that one thing to keep in mind is that the 5 blades will add a small amount of stern lift, which may effect handling as you know it with the 4 blades. (It may not be dramatic)
The best solution would be to have the props tweaked with some cup to help pull the bow up a bit and offset the stern lift.
I'm sure the professionals will chime in.
Once the 5 blades are set up you will leave the 4 blades on the shelf, night and day hole shot, mid range cruise and punch...just my 0.02....

Maximus?

Agree.......I dropped slip down to 10.5% when I went to 5 blades. I had been running 32P 4 blades for years and made it about 25 hours with 5 blades and lost a drive. Sold the boat soon after (coincidence) and the new owner lost a drive about 25 hours later. They have better mid-range because they bite the water much better. If you surface them and have too much power you are more likely to break something (I made 700 ft/TQ full dressed)

going to 5 blades cost you a drive??

I just drank the cool aid and ordered a set from cutting edge well see how they work I already had good slip numbers right around 9% not super concerned about all out speed just safety and drive ability

keep me in the loop w/your results. How do work 'slip' numbers?

Likely......you never know when one will let loose but I ran about 100 hours on 32P Bravos without issue. Within about 40 hours of installing 5 blades the boat broke both XR's. (keep in mind I was running more TQ than the XR was rated for) Slip is what keeps the drive from grabbing too much water at once......but that also means you will be slower.

Will do

Less slip equals more stress, no way around it. A few years ago I installed a stelling ext box on my boat , while trying different props I tried a 5 blade Maximus and almost immediately ( the same day I was testing the prop) sheared off a billet prop shaft, I had just inspected that shaft a few days before that too, my slip numbers were around 10 % or so with the 5 and 20% or so with the 4 blade labbed. I replaced the shaft and have ran the same amount of hp/tq (1000+ ft lbs) since then without accelerated failure, 5 blades can really torque load a drive with big hp, Smitty

Mine are Hydromotives.

Are Hydro's still available?

What pitch are you running on your 38? Was going to try a Merc Maximus 24 pitch on my 42.

Mercury recommends dropping down 2" if going from Bravo I to the Maximus 5 blade...agree or disagree?

2 inches sounds right IF your using the same diameter (Maximus come 15 5/8 vs Bravos at 15 1/4)

for my application 30P Bravos were the fastest, running 86 at 5,600 rpms and 48 at 3,500. 32P Bravos were 83 at 5,300 rpms and 54 at 3,500. 28P 15 5/8 maximus were 83 at 5,250 rpms and 58 at 3,500 rpms.

Thanks for the test results. What boat, length and motor?

Formula 382 fastech. 630hp/700tq motors (dyno'ed fully dressed with ALL accessories-not dyno headers and water hose in the front)


As I said in an earlier post.....the 5 blades tore up the drives IMO.

you mean the 5blades and 700ft lbs

yeah, that too :)