Remarkable performance increase with new prop on 251....

[Pro251WA]

If you have a fully-loaded 251 and aren't happy with the performance, try a new prop.

I have a 2000 251 with a single Optimax 225. After I bought the boat two years ago I started searching for performance specs. They're practically non-existent. The Proline test boat had very little fuel, no hardtop, and ran with twin 150's. My 251 has every available option (V-berth extension thanks to a7ewizard   ) and is heavy.

The boat had the standard Mercury Vengeance 17p. The Mercury website still says that's the right prop and pitch for the weight and use of my boat with the 225. No way is that accurate. The 225 WOT range is 5150-5700. I've learned that it should easily spin up to 5500-5700. Before the prop change, my WOT was 5250 with a top end of 32.

After discussing the issue with other owners and boat people, I became much more educated about prop slip etc. And Ken from PropGods.com in Florida has performance specs for a 26Walk with Honda 225 very similarly outfitted as mine. Those numbers were incredible compared to what mine were...but now are.

The new prop is the Inertia 14p. There were similar improvements across the board but I'll post a few specifics. New WOT is 5650 reached easily. I didn't know what hole-shot was until now. Tabs down and engine trimmed in, up and on plane right now. Previous cruise speed of 25mph was achieved at 4500-4700 depending on load and conditions at 1.8mpg. New cruise speed of 25-26 at 4000-4250 getting 2.44mpg. That's a 35% increase in fuel economy! Truth is I actually get better mpg at higher speeds like 27-28 at 4400-4500rpm approaching a 40% improvement in mpg, but that's not my favorite speed. Top end went from 32 to 39/40.

In the gulf we get ideal conditions a lot which is nice. And while getting 2.4 mpg at cruise is stupid compared to a car, getting a 35%-40% mileage increase for the price of a prop is sweet.

[231CALIFORNIA]

2.4 mpg CRUISE EXCELLENT on the larger boats
especially if you have the water conditions to obtain it regularly.
I used to get 3-4mpg w/ a 20ft boat ,351 ford 4bbl now im happy if i get 2  with a 231 wac ,but i still l ike bigger boat much better.

[Bruce03]

Thanks for sharing on this subject, Cal.  It's very hard to pinpoint what needs to be done other than by hitting upon it by hook or by crook!    

FYI, I get about 1 MPH with my 3250 and twin 7.4's, and just found that my trim tabs were not working, so I have my work cut out for me for the spring.  I've never had a boat with trim tabs and my mechanic didn't "remember" to fix them, even though they were noted by the surveyor and they were asked to fix them.... grrrr.  

[231CALIFORNIA]

PARTof my  "economy" not being great  is most of the time the chop where i fish keeps speeds at low plane and even below.
She is carrying 3 batteries, 138  gal fuel, 4- 200+# men, 10horse kicker,240qt icechest , 50+#ice,couple hundred# , provisions spares,tackle,2anchors etc.

economy is much better in nonbattle trim
half fuel, no kicker. in the bay,2guys, 2beverages, 23-24knots, bow up economy nearly doubles.

[C-Lark III]

PARTof my  "economy" not being great  is most of the time the chop where i fish keeps speeds at low plane and even below.
She is carrying 3 batteries, 138  gal fuel, 4- 200+# men, 10horse kicker,240qt icechest , 50+#ice,couple hundred# , provisions spares,tackle,2anchors etc.

economy is much better in nonbattle trim
half fuel, no kicker. in the bay,2guys, 2beverages, 23-24knots, bow up economy nearly doubles.

Just a quick note, california --- Consuming the beverages does not automatically lighten your load --- It's a 2 - step process !! 

[C-Lark III]

Thanks for sharing on this subject, Cal.  It's very hard to pinpoint what needs to be done other than by hitting upon it by hook or by crook!    

FYI, I get about 1 MPH with my 3250 and twin 7.4's, and just found that my trim tabs were not working, so I have my work cut out for me for the spring.  I've never had a boat with trim tabs and my mechanic didn't "remember" to fix them, even though they were noted by the surveyor and they were asked to fix them.... grrrr.  

Just a quick side note for Bruce and others --- My Proline 2950 is pretty heavy in the rear, with twin diesels.  I have Bennett 12"wide X 9" deep trim tabs, and they are just barely enough.  I decided to see if I could increase the lift with larger tabs, and contacted Bennett.  They told me about an item that they sell that will increase lift about 50 % without major modifications -- They make drop fins, that attach to the edges of the tabs.   If you have flat bottom tabs with no dropped edges, these fins with give you the dropped edges.  That keeps the water under the tabs better, improving the lift.  The good news:  They cost about $30 for the pair !  So if anyone out there needs more lift on their tabs, you might want to check them out with Bennett.
 

[a7ewizard]

Just a quick side note for Bruce and others --- My Proline 2950 is pretty heavy in the rear, with twin diesels.  I have Bennett 12"wide X 9" deep trim tabs, and they are just barely enough.  I decided to see if I could increase the lift with larger tabs, and contacted Bennett.  They told me about an item that they sell that will increase lift about 50 % without major modifications -- They make drop fins, that attach to the edges of the tabs.   If you have flat bottom tabs with no dropped edges, these fins with give you the dropped edges.  That keeps the water under the tabs better, improving the lift.  The good news:  They cost about $30 for the pair !  So if anyone out there needs more lift on their tabs, you might want to check them out with Bennett.
 
[/quote]

I replaced my originals with these drop fin type. I would say they helped reduce the minimum planing speed a little. I had a problem with just one of them......The drop fin also catches the flow as it rides up the "V" and wants to push the tab out. Make sure the bent metal catch is sufficient to hold the tab in the mounting plates.

[Gulfwindx]

Question What mounting holes is your Opti on. Starting from top mounting hole being number 1.   Thanks in advance.

[Gulfwindx]

Question I have an "Enertia' correct spelling
 15X15P on my WAC 251/225 opti max is it posible there is a differance 14p v 15p??

[ozjamie]

i know its a bit of an old thread Pro 251 Wa but do you no the prop that was recommended for the 26 walk with the Honda 225 ,i am waiting delivery on a 251 to Aust with that motor but not too sure of the prop she's spinnin,any heads up in advance would be much apreciated
cheers jamie

[Aussie 251]

Jamie, you should be able to find the info on propgods.com, search for honda or enertia. How far away is the 251 , remember I should have a couple of contacts around with various props you coud try on the 225, including a solas 4 blade 14 pitch which came of my old honda, I still think the powertech 4 blade OFS will be a good option, but it sounds like they are getting good results with the mercury enertia.
Mark

PS please give me another call, I have lost your contact details.

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