Thought I'd share some prop test numbers with ya'll

[Ron V]

My next door neighbor and the old lady across the street probably think I'm loony, taking the boat out for 1/2 hour at a time, but I've been playing with props on my new setup the last couple months and here's what I've found. Figured it never hurts to share what one finds, even if it only applies to a particular rig.

Tests were made on various days in various weather and water conditions, but all of them were run in weather that at least gave them half a chance. The speeds and RPM below are from the Faria gauges in the boat. The speeds are obviously optimistic, but accuracy is not as important as relative readings here. This is on a box stock 2.5 150 carb motor with 1.87 gears on a 18 1/2' rounded V-bottom (no pad), no setback, mounted at a 23.5" transom height (shaft approx. 3.5" below the bottom at neutral trim). Oh yeah, and to paraphrase Danica Patrick, "I weigh all of 125 lbs."

27" large hub Laser II (stock): 76 mph @ 5600 rpm
27" SRX (stock): 77-79 mph @ 5800-5900 rpm
27" SRX (worked and beat up): 78 mph @ 5600 rpm
25" SRX (worked with LOTS of cup in the tips): 72 mph @ 5750 rpm
26" ET cut chopper: 76 mph @ 5800 rpm
25" Shooter: 75 mph @ 5800 rpm
26" Trophy Plus (one damaged blade filed out): didn't quite get it topped out (cops were nearby and there is a speed limit so I had to act quick), but got 70 mph at approx. 5300 rpm and it was still pulling. 24" Trophy (an old one with the rubber hub): 68 mph @ 5950 rpm

The Laser II had a lot of steering torque on this rig, was moderately responsive to trim, and was unpredictable. Quick out of the hole for a 27".

Both of the 27" SRX's were the best handling of the 3 blades and fly the bow beautiful. A 15 - 65 punch with one takes about 6 seconds. The worked one had less blow out coming out of the hole.

The 25" SRX hooked up good out of the hole and lifted the bow well.

The cut chopper didn't plant the stern hard enough, took a lot of trim to lift the bow, and consequently was borderline undriveable. It also didn't pull much harder than the 27" SRX.

The 25" Shooter is appropriately named; it was absolutely ferocious out of the hole; hit 65 mph on the speedo in around 8 seconds flat from a dead idle and was very stable. It hit a brick wall in the trim department at a certain point, but who cares, the bow was well out of the water by then and was only 3 mph slower than an SRX. Not bad for a holeshot prop.

The 26" Trophy Plus had a mountain of bow lift and strong acceleration, but was too much pitch for a 4-blade on this rig. The 24" Trophy hooks up and handles good; it still takes a back seat to the Shooter for performance given the slip numbers and top end, but that's not what I bought it for. There is also a difference in the slip numbers (all other things being equal) between it and it's newer cousin, the Trophy Plus.

Thanks to Sam Baker, John Walsh, and Don Miller for the prop loans.

[imq707s]

Were those speed number from your speedo or GPS? 79mph seems pretty fast for a non-pad hull with only a 150 on it.

Looks like your 27SRX ran the fastest....that's what I run on my Vegas. Out of all the props I've ever tried, that 27 SRX (worked by DAH) is the fastest I've ever found.

:D

[Fish]

thanks for posting the numbers, I am sure it will save someone a lot of time going through the same steps you had to. Sounds like you really got her running well with no pad, congrats.

fish

[carpetman]

At 100% efficiency (0 prop slip), a 27" pitch prop @ 5900 RPM's is 80.669mph. If anyone cares..the formula is the pitch divided by 12 to get the feet in one revolution of the prop,times the RPM's, divided by the gearcase ratio(1.87) times 60 to get the RPM's to rev. per hour, divided by 5280 (statute mile). i.e. 2.25x5900=13275. Divided by 1.87=7098.93. Times 60=425935.828. Divided by 5280=80.66mph. GPS recommended. A go fast, hooked up will get amazinging low prop slip with the right set-up, but 0 prop slip could only happen downwind in a wonderful dream with beautiful women feeding you grapes while rubbing your feet :D and (you know the rest)lol. Cool to see someone putting up some #'s! BTW, not bad for a 150! Mike

[Ron V]

Hey guys, notice the first part of my post where I said the numbers were from the gauges and that relative numbers were what was important. I didn't want to "guess" the real speed since I didn't have a GPS with on all of them.

Faria speedos have a 9-10% optimistic error. I've GPS'd it at 70.94 when the speedo read 78, though it is more accurate in the 60 mph range; 60 on the gauge is 55-56 on the GPS. With the slip numbers I've calculated, I feel the tach is likely 100 rpm high or so, but I'm not sure. There may be a couple more mph left in the rig, but not too likely. j.iverson had one of these boats with a hopped-up 2.4 200 on it and best he ever got with a 6" setback and Bob's cone was 78 mph GPS. Brent Shaw had one with a 150 Suzuki and a 6" setback, and best he got was 73 GPS. The Suzuki was 10 more cubic inches than my motor and fuel injected; that alone would make up the 1-2 mph difference probably.

[pyro]

Either the speedo or the tach is off. 2% slip with the stock SRX is unlikely. Whether it's 72 at 5900 or 79 at 6500, either way that that's good top end for a 150...