4 blade prop vs. 3 blade prop

My 04 Supra Launch (direct drive) has the 3 blade prop on it, but I read that a 4 blade prop was an option. What will the 4 blade do that the 3 blade won't do? I'm wondering if I should make the switch.

Ronia,

Is that approved on LSL? I haven't seen it yet, but would love too.

Tim

Nope!!!
We've sacraficed beautiful LSL for a beautiful boat. I'll have to post a pic.
The boat is just huge and so awesome with an incredible wake.

Ronia,

FYI, we tested a number of props on that boat to get the best hole shot and not sacrfice too much top end speed. The Original prop was a SS OJ 13x11 4 blade prop. It did okay. We then switched to an OJ CNC 4 blade 13x15. Better hole shot but just didn't feel right. Then we tried the 3 blade OJ CNC 13x11.5 and it had amazing hole shot and acceptable top end. That is what the boat has on it now.

Thanks Jon. That's awesome!!! I was curious what the differences were.
We love the boat by the way ... already up to over 250 hrs!!!

3-blade Acme is the way to go. $310 shipped in CONUS.

props w/ lower degree of pitch (the second number) let your engine apply higher RPM's (and horsepower) for a given speed.

I am also looking at upgrading my prop from the stock 3-blade. If you go to FAQ at acmemarine.com you send them your specs and get a recommendation. Let them know how much ballast, etc. I also got a quote from Karl.

Right now I'm having some other work done, and the dealer said I could have my stock prop "re-pitched" for about $100. They can only drop it 1 or 2 degrees. Has anybody else tried this?

so the lower the degree of pitch, the more gas you use because your engine is revving higher?

in theory, yes. but think about how long it takes your boat to get on plane w/ the throttle hammered. I think there's another thread on props and gas prices.

well i have a great hole shot now ... but i was just curious what the difference was in props.

The primary reason most people go to a 4-blade is to get better hole shot. It is effectively a slightly lower gear, and if you're loading the boat with tons of ballast, you might need the lower gear to get going. I'm looking at it for that reason - to put less strain on the engine and tranny while under a load.

Re-pitching the prop could do the same thing. Not to hijack, but anybody got any feedback on that idea? (hey, it's related)

I would go to ACME Marine and discuss this 3 blade to 4 blade issue with them. I have just purchased an ACME 13x11.5 3 Blade, and in discussion with them, this is their best recommendatoin for holeshot, planing, and top speed. I am personnaly not that interested in top end as all we do is wakeboard. I will give up a few mph top end for a more consistant/solid pull on the wakeboarding end. They swear by thier 3 Blade.

I would not repitch a prop. Purchase the right blade for the right pull, keep the old one for a spare.

The reason why 4-blade props were the norm was due to the ease of balancing the prop. The hand-finished props common today are very hard to balance. The speed freaks know this and will buy an expensive prop and send it out to be balanced and "blueprinted," thinning the blades to a uniform cross section. This results in a 3-5% increase in efficiency and speed. Most the skiers were too cheap for this and just stuck on whatever came out of the box. The barefooters, however, used the technique with good effectiveness.

Acme came along and decided to CNC machine the props so they would perform great out of the box with great balance. Along with increased surface area, a better cross section, and better alloys, the Acme 3-blade performs better than most hand finshed 4-blades.

Now, Acme testing has revealed that on many V-drives, the 4-blade does do better than the 3-blade for wakeboarding. Don't have a hard answer as to why. But that is the result of testing. On direct drives, the 3-blade outperforms the 4-blade most of the time on most boats. The difference is very minimal and hard to measure. It is largely personal preferance.

If you want to have a 3-blade Acme shipped in CONUS - $310.

I purchased a lower pitch 4 blade ACME for my 04 X2 from Karl at boarditup.com. There is absolutely no comparison to the stock OJ. The ACME planes twice as fast when weighted, and still has about the same top speed.

I had my OJ re-pitched to the same spec as the ACME when it was being repaired, and the performance is still not in the same universe as the ACME.

Karl, I think the 3 to 4 blade performance is not D-drive to V-drive but 1:1 tranny to gear reduction. I have a V-drive with 1:1 tranny and Acme recommended a 525 3 blade. I know they recommend 4 blades for the VLX, SAN & X-2 which all have gear reduction.

I did a quick comparison by placing an old 3 blade SS Michigan Wheel prop on top of a new ACME 3 blade. I wish I had a picture, however, the surface area of the ACME dwarfs the surface area of the old prop. I would guess about 35% more/blade. What a difference in surface contact area. It's no mystery as to why the ACME is superior.

what about gas consumption. Does anybody notice a difference? I am thinking of going from what I believe to be a 13x13 OJ Legend on a tige 2100i running 1100+ ppl to a 3 blade acme. Should I go for the 3 blade made for 1000 lbs or 2000lbs+ (varying degrees of cup) will I see a significant change in operating RPM and gas consumption? My OJ can get sluggish out the hole with a couple ppl and 1000#s ballast but it still holds a speed... no PP... Is it worth it?

The rpm thing does have an influence. However, a MC 197 with a Power Slot gear reduction or a CC SN 196 with gear reduction still does better with the 3-blade. My personal belief is the prop rpm at use, not WOT. Slower favors more blades.

The surface area of the Acme 3-blade is more than the normal 4-blade by far.

In my opinion, the least expensive performance upgrade is the proper Acme prop on the boat.