2520 XL F225 with new 14.25 X 17 Prop: First Report

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Well-known member
Mar 22, 2006
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Franktown, Virginia 23354
Prop Stuff….

I now have the Stilleto 14.25 X 17 three blade stainless steel prop purchased from Overtons’s for 309.95.

As you know….. Most of us with the 2520XL and F225 have been using the factory prop which was a 14.5 X 19. On my boat WOT was never over 5300 rpm.

The general consensus was that the engine should max out around 56 to 6000 depending on the source. Having a wide open throttle achieving only 5300 suggests that at some points in the power band the engine would be lugging and that this is not a good thing.

With the old prop I was happy with the performance and would not have considered changing if it weren’t for the internet and the ability to learn and compare data.

Armed with the notion that better performance was possible and eliminating the potentially harmful “lugging” I went ahead and got the above mentioned prop.

Several days ago I was out with an unusually heavy load and could not properly compare performance (in general I was not happy with the numbers I was seeing).

Today I went out with my wife, about 130 gallons of liquid gold, and about 20 gallons in the live well and another 12 or so in the fresh water washdown unit.

With the older prop I never took down accurate numbers throughout the range but on calm water at 4400 rpm a speed of 27 to 28 and a fuel consumption of 11 to 12 gph seemed to be the sweat spot.

Today with the new prop…. About a 10 mph wind with less than a foot chop (will have to compare later with the slick cam….) trim tabs were up for all these numbers and the engine trimmed for best ride… about a 2.5 on the Yamaha meter FWTW.

Rpm – speed in mph from gps – gallons per hour 87 octane

4600 – 24.5 – 10.7
4600 – 23.6 – 10.8
4700 – 25.5 – 11
4700 – 26.6 – 11
4800 – 27.4 – 11.4
4800 – 28.2 – 11.3
4900 – 28.0 – 11.3
5800 – 34.0 – 16.6

5800 is WOT although I did see it flick up to 5900 briefly.

The numbers do not tell the complete story.

There is a big difference in the ability to get up on plane…. Don’t ask me for times ….. I don’t know them but I can feel the way the engine winds up and the boat feels. It gets up to speed faster and up on plane quicker.... not important to me but might come in handy some day.

It will be interesting to see how things go in the future on glassy water and out on the ocean……… I recall a day last year on the ocean when I was coming in with a following sea……. In the inlet when you start to have that sensation that the boat is getting sucked into the wave behind you….. giving it the throttle and little to no increase in the rpm because…. Well I guess the engine was lugging and maxed out. I think this prop will perform differently.

When using the Navman in the MPG mode I never saw better than 2.3….. I did not write down all the data in MPG so I can’t comment further on that.

All in all I’m happy. I’m not convinced completely which will cause the engine to wear out sooner….. more rpm’s over the lifetime versus lugging….. seems like most say lugging. As long as this engine keeps working until Yamaha comes out with a 300 hp four stroke I’ll be happy.

Esfishdoc: I'm with you on the 300hp 4 stroke. I hope I will never "need" one, but that would be the power of choice for my 2520DV.

BTW, it seems that you are in good shape with 5800 RPM's.

Richard... I'm with you on the 300 hp 4-stroke, but only if I find that damm pot-o-gold first... :D

I've done a lot of prop testing as well. I've tried 3-blade as well as 4 blade, and am presently wearing a 15x17 Solas AL prop on my 2520 MVSC with a Yammie 225 OX66.

I know this is apples to oranges, as you have an F225, but at least the hulls are similar...

The 4-blade worked well in some respects, but prop slip was way up, most probably due to the weight of my boat. The 3-blade Solas has been great, but I'm onlly getting 5000 rpm at WOT. Recommended for my motor is 5000 to 5500.

I have a SS Merc Mirage prop that I got from B-Faithful that I want to try, though I'm not certain of the exact size. I believe that it is a 14.5x17, but that needs to be tested...

Like you, I'm still looking for the magic size for my boat. :)

FWIW... I did find an excellent prop shop that I intend to work with. http://www.WildCatProps.com
I've seen, and experienced their work, and I can tell you that they are first class... Once I get my boat dialed in, look for a detailed report. :wink:
I am installing a 14 5/8 x 15 4 blade Revolution 4 on my boat this weekend. The 17" in version of the same prop reduced my prop slip to under 15% but limited my WOT to 5350 with an load and 5190 with a heavy load. (it is recommended that I am in the upper half of 5000-5750 for engine longevity) I am told that by going to a 15 I will gain 300 rpms. The merc runs a 1.75 gear ratio. I will let you know how it does.
B-Faithful, I'm about to get my new (to me) 25 MVSC in the water and I'd love some advice from a fellow Merc owner. I've been trying to figure out the best prop for my set-up -- a 225 Opti -- as the prop that came with the boat was simply a spare and the wrong size. I'm inclined to go with an aluminum three-blade at first, on account of the thousands of rocks around my area. What would you suggest?
Sow&Pigs":vl3t2bvp said:
I'm inclined to go with an aluminum three-blade at first, on account of the thousands of rocks around my area. What would you suggest?

If you are in a rocky area, I'd definately suggest aluminum.
Better to sacrifice a prop to a rock, then a lower unit on your motor. :shock:

I think you need to go with a stainless steel wheel. Your boat is too big and heavy to not get the least flexing wheel possible. Merc props come with a flo-torque hub that will protect you more than going with an Aluminum blade. Here is the info on a flo torque:

http://sites.mercurymarine.com/portal/p ... ema=PORTAL

If you havent seen the prop selector on the merc site. I suggest you start there. here it is for you (althought they dont really have a hull style that matches the lower deadrise boats):

I personally think after running a bunch of props that the Merc Rev 4 15" will be the prop for you. I cannot blow the prop out no matter how hard I turn or trim the motor and my prop slip went from over 20% to around 15% with the 17" Rev 4. I just couldnt get enough max rpms with a load. I will be putting the 15" rev 4 on my boat tomorrow. I will keep you posted.

Here is what I think would work well for you:
15" Rev 4 (performs like a 17" 3 blade according to merc dealer/site)
17" tempest (Glenn E on THT thinks it is Mercs best 3 blade after a lot of prop testing for Merc)
17" Mirage plus (rev 4 and mirage plus were what my dealer recommended)
17" Enertia (new prop- will be out this summer in 17"--ultra thin and ultra strong)

Good luck!
Rpm – speed in mph from gps – gallons per hour 87 octane

4600 – 24.5 – 10.7
4600 – 23.6 – 10.8
4700 – 25.5 – 11
4700 – 26.6 – 11
4800 – 27.4 – 11.4
4800 – 28.2 – 11.3
4900 – 28.0 – 11.3
5800 – 34.0 – 16.6

5800 is WOT although I did see it flick up to 5900 briefly.

So, given that those numbers what would you call your optimum "cruise" speed?
rangerdog":389bu1yr said:
So, given that those numbers what would you call your optimum "cruise" speed?
Almost 2.5 mpg @ 4800 RPMs, 28mph, is best.
Pork, I am lazy and do it here:


ESDoc, you may want to try a more "cupped" 15" prop. Your slip at the upper end of the rpm band seems like you are "blowing out". I had the same problem with a 17" AL black Max. Even if you reduce your slip to 18% with a 15" prop, you will still reach the same max speed. For info on props see here (look at "Cup"):

http://sites.mercurymarine.com/portal/p ... ema=PORTAL

For example, I had a 17" AL 3 blade prop with a diameter of 15" and hit a best 39.4mph at 5750rpms on calm water. I would also ventilate a lot in sharp turns. I went to a 4 blade SS with a smaller diameter but a lot of cup and rake and now have seen 41.8mph at 5350rpm. I also cannot get it to ventalate to save my life. My cruise at 4000rpms went from 26-27mph burning just under 10 gph to 28-29mph at 4000rpms burning right at 10gph in calm water. (my boat is lighter, narrower, and only has 10 degrees of transom deadrise than the parker xl). I should hit my target max rpm of 5500 by raising my engine a hole since my antiventilation plate currently sits just below the surface when running and since props with more rake, cup and blades can run closer to the surface.
I found the site and poked in my numbers. I get 8.6% slip for the twin F-115s each turning a 15" x 17" SS prop.

I wonder where the intersection point is concerning the efficiency of a single verses the low slip of twins (based on the large surface area of the two props verses a single prop)?
hello i just purchased a 2510 wa with a f225.first trip out was 5 13 06 and coming back in i thought this boat should have a little better response out of the hole and tp end . i logged on here and the first post may have answered myquestion .i will check my prop size this week and compare to youll numbers this is a awsome site! thanks
I have the same boat and the F225 is on a bracket and a painted bottom. with a 15 1/4 x 17 SS I can get 38-39mph with light load I can see 40mph if everything is just right. Comes out of the water just fine, but never really worry about a hole shot.
thanks for the reply guys .i ll check my prop size.im not looking for the speed more so optium performance from the motor per gallon of gold.the idea of the motor lugging concern me .my boat has the notched transom i dont know if this makes any difference or not .sounds like i on the right board to gain alot of knowledge thanks again :D