Prop For a Sea Born FX25

[Gulfisher12]

I just purchased a Sea Born FX25 with a 300 Yamaha. It has a PowerTech OFX 20P 15-1/4" dia prop. I am having a few issues.
#1 Motor will only turn 5000 RPMs with a normal load 52-53 with a light load.
#2 Motor wants to cavitate on semi hard turns and on take off if not ALL the way trimmed and "jacked" down. Boat has a jack plate and stepped hull.
#3 Hardly any bow rise at all. This isn't a big deal in calm seas but on the gulf coast we get very short wave intervals and rough conditions often. In certain situations I need to get the bow up and I simply cannot do it with this boat.
Any guidance is greatly appreciated.

Thanks

[ken2]

If you just purchased that boat, I'd tell the dealer to swap you out for a lower pitch OFX4.

Normally that prop has great traction and does not ventilate easily. Maybe the one you got isn't cupped as well as normal.

Just to make sure you get this right on the first try.
is that speed on GPS or speedometer? I ask because your at 2% slip, and that is super low. Not a bad thing, just a little odd.

2. You said 52 MPH with a super light load. What speed do you get when you load it up like your actually going to run it?

Taking a guess, your going to give up a couple mph with your load.
I'd go 17 pitch OFX4, acceleration would be MUCH stronger. you'd still get 50/52 MPH but you'd be turning close to 6000 RPM.
And hopefully the 17 would be cupped well and not ventilate.

[Gulfisher12]

Thanks for the feedback Ken. I have gotten with the dealer, just waiting on them to get back to me.
When I said 52-53 above I meant 5200 to 5300 rpms with a light load and by light load I mean less than half a tank of fuel, me and 1 other passenger. With a normal load......full tank, 100 lbs of ice, 2 full live wells, 2 adults and 3 kids I can only get 5000 rpms and about 44 to 45 mph per the Yamaha gauge. GPS is telling me 38 to 39 knots.

The other issue I am having is virtually zero bow rise. If I go to a 3 blade would that help me get the bow up? Normally not an issue but in rough conditions I like to get the bow up a little.

Thanks for the quick reply and your help!

[ken2]

Well, I would drop down to a 17 pitch regardless.
The OFX4 normally gives a lot of overall lift. 20 is just way too much pitch.
but a 17 pitch Yamaha Saltwater Series, or Mercury Mirage Plus would be good options as well.

Speed seems to be all over the place.
This ad is claiming 57 MPH with a 300 verado. https://www.saltwatersportsman.com/b.../sea-born-fx25
These guys tested it, and got 50 MPH out of a 300 Verado https://www.boatingmag.com/boats/sea-born-fx25#page-7
Your getting 45 MPH.

Drop to a 17 pitch, and see what happens.
If they will swap you out for free, great, it should be a big improvement.

[kdenap]

Gullf Fisher 12,
I just became a member, so here is my theory on your boat. I purchased the same Sea Born FX25 3- months ago. Spent a lot of time getting the correct prop. Tested 6 props from 3 companies. I can tell you my boat hated a 4-Blade. It needs a Bow-Lifting Prop and not a stern lifting prop like the OFX.
The boat is balanced to ride on the step-lift. If not you will plow the front and loose 4-5 mph. I use the LFS-3 23P ( Suzuki can run a 16 x 23 because of the gearing). This prop beat out the best of the best..real world performance . I would call Power-Tech customer Service and ask what line of prop has the characteristics of the LFS but in a 15.25 diameter. GET IT! Some boats hate 4- blade props and I have been finding out that single engine -step lift boats hate them. I have a Nautic Star and a Yellowfin in my club and those boats like mine (FX-25 ) performed better with a 3 blade. Maybe Ken will chime in
on this and make a suggestion. My club has bought props from him in the past and his read on this is usually on point.

[ken2]

The OFS and LFS have very similar blades styles, LFS is just larger diameter 16 inch vs the 15 1/4 diameter OFS