4 and 5 blade props?

[hugo]

so are the 4 and 5 blade props realy worth the money for the added gains or if my numbers are good should i leave well enough alone? and will they improve MPG any or not enough to justify the cost?
thanks guys.

[Bushwacker]

Don't know about a 5 blade, but a 4 blade prop changed the handling of my boat from totally unacceptable to perfect! With a 3-blade 14.5x17 Stilletto, it would not plane below about 20 mph and speed was unstable with a very sensitive throttle below about 25! With a 15.25 x17 Merc Mirage 3+ it was a little better at about 14-18 mph min planing speed but still not as good as with my old 300 lb motor on the transom. With the 4 blade prop it now has an awesome hole shot and is very stable with a very heavy loads at any speed from about 12 mph to WOT! You really need to try one to appreciate the difference. As I posted earlier, you're welcome to try any of my 4B props if you come to the Long Point gathering!

In my book, the extra $100 or so you'd spend for a 4B prop is a bargin for an improvement that totally changes the boat's handling characteristics! I think it's an additional expense that should be included when you're thinking about screwing up the CG of a 20 by adding a bracket with a heavy motor on it!

[hugo]

that sounds great, thanks for the input. i will definetly try and get my hands on one. i see you stayed with 17 on all three props, im running a 19 now with good resluts is it advisable to stay at a 19 pitch or drop to an 18 or 17 pitch? did your rpm drop when going from 3 to 4 blade as some say it will? im maxed at 5500-5600 now and dont want to drop any more than that. i beleive my motor is rated at 5800 max rpm.

[Bigshrimpin]

I tried a Merc highfive a while back when I owned a 20MA. It's sOoooo smooth and vibration free compared to a big 3 blade prop like the mirage plus. I could bank the boat hard 47mph and hold water . . . most fun I had driving the 20. Cruise and Top end numbers were lower than mirage plus by 3 or 4 MPH. If you get one of these props they are designed to run a bit higher than a normal 3 or 4 blade prop.

[shine]

Love my Merc 4 blade, would not consider a 3 blade for my boat. Holds bow down, boat runs more level, I can keep the motor mounted in top notch. This weekend I was getting close to 3.8 mpg (running down wind and empty boat _

[hugo]

well im definetly sold on the idea of going 4 or even five blade, i would still like to know if i should stay at 19 pitch or drop to 17 or maybe 18 if i can find one in an 18.

[tautog_33]

Originally Posted by shine

Love my Merc 4 blade, would not consider a 3 blade for my boat. Holds bow down, boat runs more level, I can keep the motor mounted in top notch. This weekend I was getting close to 3.8 mpg (running down wind and empty boat _

Same results here went from a three blade 14.5" x 17 mercury quicksilver to a four blade Solas 14.5" x 15 pitch. The holeshot improved as well as my cruise the boat ran level I did lose 2-3 mph on the top end. As mentioned many times on this site a stern lifting prop works very well on these hulls I am a believer.

[gofastsandman]

Originally Posted by Bigshrimpin

I tried a Merc highfive a while back when I owned a 20MA. It's sOoooo smooth and vibration free compared to a big 3 blade prop like the mirage plus. I could bank the boat hard 47mph and hold water . . . most fun I had driving the 20. Cruise and Top end numbers were lower than mirage plus by 3 or 4 MPH. If you get one of these props they are designed to run a bit higher than a normal 3 or 4 blade prop.

Prop freaks CSC style... Great info. The prop testing at Long Point could be memorable if any want to have some fun. I`ll bring my 5 or 6. It never ends. Robert sr swears he can make magic outta my ole Mich. match for 80 clams. Says it has the thickness for his magic turning profile...? Are heavy props loading more shear to your LU? Pretty happy with my SSt1 3 bl @ 15x16. My motor is light and on the transom. The more I read and digest, the more I learn. The newer machined hub systems are indeed smooth thru your hand. Wouldn`t have thought you could feel that.

[sidelock]

Don't mean to hijack this thread but there seems to be so much knowledge & experience on props in this thread that I just could'nt help but to ask. What prop would you all recommand for an 18SF with a 1998 Yamaha 115 four cylinder two stroke ? I don't know what size prop is on it presently & the boat is in storage but I do know that the blades were ground down when I bought the boat. Someone told me they were ground down because they were too big & would hit .

[Bushwacker]

[QUOTE=hugo;212056]that sounds great, thanks for the input. i will definetly try and get my hands on one. i see you stayed with 17 on all three props . . . QUOTE]

My 4B PowerTech is a 15x15. I tried a 15x17 but could only turn it about 5200 at max load with my motor, which is about 165 hp at the prop. The 15P turns 5450 which is right at optimum for my motor, and it turns that speed pretty much regardless of load in the boat. It runs about 5% slip at cruise, which is pretty good. In general, you'll probably want to drop a couple inches in pitch going to a 4B because of the increased blade area. A 4B will cost you a couple of mph in top end due to drag of the extra blade, but they're typically more efficient with lower slip numbers at cruise, and of course they're smoother. I think a 5B is overkill and would be hurt by additional blade drag.

I think the Merc Enertia is a pretty good 4B prop for your motor, although I think the Michigan & PowerTech props have a more robust 2-piece hub system. All the prop web sites have a prop calculator where you plug in all relevant boat info and what rpm you turn with current prop and it'll recommend a size. Ken at PropGods over in Tampa is another good source for props and info.

In general with a stainless prop if it's not the perfect size, I think it's best to have too little pitch than too much because a good prop shop can always add more cup to the blades, but it's pretty hard to remove it. When testing props, it's best to test with the heaviest load you think you'll normally run; fill some coolers with sea water for ballast if necessary to simulate max load. I think most folks don't do that and end up with too much pitch as a result. As Fr. Frank (who probably knows props better than anyone on the CSC forum) says, you want to prop for max rpm at max load. (or optimum rpm if you can find out what it is. E-Tec is the only manufacturer I know of that publishes the OPTIMUM rpm range in addition to the "recommended operating range", which is the only number most dealers seem to know about. The "recommended operating range" for my 150 is 5000-6000, but OPTIMUM range is 5400-5500.)