Prop ? F300UCA

[Lucky John]

Ok I have been running my new 2520xld for a little over a month now. It came with a Yamaha 15 1/2 X 17 Saltwater series II prop.
I know this is a heavy boat, but I was wondering if changing the prop to a possible 4 blade would improve my fuel and ability to plane easier. As of now it takes about 35-3700 rpm to bring her up on plane and pretty much can't run below 3800 without falling off plane.
I ran to a local canyon on Friday and wasn't impressed with my fuel numbers, I burned 113 gallons for approx 180mile round trip.
Any suggestions?

 

[moose8420]

What is your WOT RPM? I found a 15-3/4 x 15 (3) blade prop worked well for my 2520MV hull, but I too need to be above 3800rmp to plane unless I trim the motor and tabs way down. I have the F300 as well.

 

[Lucky John]

WOT I am at 5700 and zipping along at 43 mph

 

[shawnee83]

Ok I have been running my new 2520xld for a little over a month now. It came with a Yamaha 15 1/2 X 17 Saltwater series II prop.
I know this is a heavy boat, but I was wondering if changing the prop to a possible 4 blade would improve my fuel and ability to plane easier. As of now it takes about 35-3700 rpm to bring her up on plane and pretty much can't run below 3800 without falling off plane.
I ran to a local canyon on Friday and wasn't impressed with my fuel numbers, I burned 113 gallons for approx 180mile round trip.
Any suggestions?

John, I'm a broken record on this but what can I say....I love my Permatrim. When I got my 2120 with the F225 it took 3800 and 20mph to stay on top. She also liked to zig zag real bad at no wake speeds. With Permatrim I had much less bow rise when getting on plane and dropped my planing speed to about 17. She tracks nice and straight now too at slow speeds. I'm sure you don't like the idea of drilling on your brand new F300, don't blame you there. A Permatrim may help but I don't know anyone who has done it on a 2520. Obviously it's a much bigger boat so the results may not be the same. Call Ken at Prop Gods for advise on that? I'm thinking a 15x17 but that may not help your planing rpm/speed any. I'd make sure your motor height is right first then consider the Permatrim. Those 2 may fix both issues....planing and increase WOT rpm and speed?

 

[Lucky John]

I will give them a call and hear what they would suggest. Looks like another weather window on Friday so I will be going back offshore.

 

[shawnee83]

Good luck with your opportunity. I was rigged and ready on Sat but my bride got sea sick at the 10 mile mark heading for the stream so I turned back for the Cape. Only need to be at 25 for the Mahi

 

[moose8420]

WOT I am at 5700 and zipping along at 43 mph

5700 RMP is on the cusp of not reaching the WOT range of the motor. I've always been told that the motor should reach 6,000rmp at WOT. If the motor is mounted too low you will definitely have a reduction in RPM's. When I had a 15 1/2" x 17" prop, I was in the 5500 RPM range. with my new prop I'm able to cruise at 4200-4300 RPM's instead of 5,000RPM's for the same speed. My modified v may handle a little different than the dead v version.

 

[grouperjim]

A 17p prop is definitely the correct pitch for that boat and the speed range it should be in. The 300 should have enough ass to swing a 15 1/2 prop. That said, take the current prop data you have and the prop to a reputable prop shop and have them "tune" it to your liking. Need a little more RPM.......they can do that either by reducing cup or changing the pitch a tad or even thinning the blades. Thinning the blades and taking out a tiny bit of cup will put you up a 100-200 rpms or so and thinning the blades will improve your fuel numbers. The yami SWS props have a lot of cup and very thick blades.


The biggest thing that will improve planning at much lower speeds and ultimately fuel numbers is by putting some hull planning surfaces in that 18 inch setback gap between the stern and the motor foot. That's why that deep v squats and doesn't want to come up. The only other advice is a simple one.......set up the dance floor so anything heavy is as forward as possible. Light weight stuff in the transom boxes like buckets of dead bait and such, heavy coolers with ice/fish up forward near the cabin door. I carried 200# of ice in a cooler in the V-berth. Also, don't run the boat full of fuel. Because of the fuel tank's location more so towards stern, it causes her to squat even more. You should be able to run on 1/2 to 3/4 tank.

Tuning your prop, adding hull planing surfaces (as Shawnee mentioned), and moving things around to move CG forward will change things dramatically. Like I always say "You got to get those fat chicks out of the back of the boat." That 9' 6" beam needs all the stern lift it can get. FWIW in my experiences an offshore 3 bladed prop at cruise usually yields slightly better full numbers than a four bladed stern lifter. Like anything there is a trade-off. Fuel efficiency versus handling. I used to run 120 mi (one way) to the western edge of the MIddle Grounds/Gulf of Mexico burning 110 gals of fuel round trip........I know.

 

[Lucky John]

Good post Jim makes a lot of sense. I will definetly adjust things on my next trip. I will find the sweet spot for this boat. I only wish I knew how much fuel I actually have in the tank with this charcoal filter slowing things down fueling.

 

[grouperjim]

John,

Your hull (25DV) with the F350 has impressive "published" fuel numbers..........very close to a heavily loaded 2320/f250 although the 2320 would never do worse than 2.0 mpg. Heck FWIW a newer 25 MV w/f250 with a rev 4 17p will cruise at about 2.2 mpg.

I am thinking that once your motor is broke in and your prop is "tuned" if I were to get 2.0 with that big wide deep v I'd be happy with that.

I am skeptical about this Yami bulletin but in the past they were usually pretty close.

http://yamahaoutboards.com/sites/defaul ... 08_occ.pdf

 

[Lucky John]

Thanks Jim. The forecast fell apart for today. My next trip I will re arrange the ice/coolers etc. I will make more of an effort to have boat trimmed out right and see what my numbers are before I start experimenting. There is a couple of good propeller places here in south NJ