Prop reco for Opti 225 on 25 MVSC?

[Sow&Pigs]

I'm wondering what the ideal prop pitch and diameter would be for the motor on my new (to me) 25 MVSC. I'm running a transom mounted 225 Optimax, with a soon-to-be-mounted pair of Bennett 24X9 tabs.

Thanks

 

[DaleH]

I'd bet $$ that a 15" diameter by 17" pitch prop, with cupping preferred, would be ideal. That is the size prop that hull wears with either the Yummie or Bomb/OMC 225hp OB on the stern.

Forget about 4-blades props too on that hull. For heavy offshore boats, 4-blade props provide not only stern lift out of the hole, but "bow lift" when up on plane. I tried a premium 4-blade on my mod-V SC and it made the bow raise so high at planing speeds that I had to drop the tabs more than usual and that took off 10-20% from my fuel efficiency. (My boat has a fuel computer tied into the GPS and with "normal" tab use, I can dial in a 10% improvement over the hull attitude with no tab use.

FWIW, my boat wears those 24x9 Bennetts and using their trimdicators, I find position #3 or 4 gives my boat that extra 10% increase in fuel efficiency in most sea states, less those where I really need to drop the bow.

 

[Sow&Pigs]

Excellent information all around. Thank you.

BTW Dale, is your boat the one pictured on the home page, the one with the tan roof? I ask because I'm planning on re-painting the deck on mine, and I like the look you achieved.

I just purchased a 1990, in great condition overall, but with three kids that huge deck with zero non-skid isn't a great idea. I was planning on using Durabak, but hadn't decided on a color. Then I saw the boat on the home page and I'm thinking that maybe I'll do the roof and fore-deck as well (I just sold a 28' Blackfin and my kids liked to jump off the tower and I'm guessing they'll want to do the same on the Parker )

 

[DaleH]

... is your boat the one pictured on the home page, the one with the tan roof? I ask because I'm planning on re-painting the deck on mine, and I like the look you achieved.

Yes, thank for the comments, that is my '92 vintage Parker. What you see there is paint and I used Pettit Shipendec 1-part enamel in "medium buff". Being an enamel, I need to recoat every other New England season, and I just heard that this paint is being discontinued . Hopefully another Mfr'r will step up to the plate, as this is a very popular trim color for downeast boats.

What I am considering doing is having Mini-Craft or Spectrum Color make up a batch of gelcoat in that tint and then spraying it as gelcoat.

... but with three kids that huge deck with zero non-skid isn't a great idea.

Yup, have been there ... less the 3 kids. I too have looked at Durabak and may go that route, as I know Bobby (Warthog5) used it on his *awesome* Mako project boat.

FYI, if you don't have "time" this season for Durabak, you can do this. Sand floor with 36-60 grit and then solvent wash, then put on 2-3 coats of West Marine's brand of non-skid paint. It was top-rated for grip and as a Best Buy by Powerboat Reports. I used it ... it will scratch if a heavy item is dragged across the floor, but it goes on fast! Once prepped and layed out with tape (I like a clean 1-2" border around the edge), you could put down 3 coats with a roller in 4-5 hours.

Best part ... it's only $24/quart and their cream color is just a hint darker than the Parker gelcoat and I thought it complemented it very well.

 

[Sow&Pigs]

Dale,

More good info. Thanks. I'm in CT so have to cope with the same weather as you. And yes, I got the Durabek idea from Bobby. A buddy and I are restoring a '72 19' Mako center console, so I spend a good deal of time on the classicmako.com website.

Now, if it would just warm up a little I could get to work on the Parker AND the Mako... :lol:

 

[Megabyte]

I played with different props on my 2520 MVSC a good bit last season, so I can give you a little insight.

When I bought my boat, it was wearing a 13 3/4x17 black painted Yamaha stainless 3-blade prop.

I did a number of on-water tests where I recorded speed and engine RPM (I don't have access to the data right now), and concluded that I had a lot of prop slip. Since a lot of people have had good luck with 4-blade props, I tested several of them.

In my case, I didn't have the bad experience that Dale did... Performance was better than the original prop that I took off, but I was still getting a lot of prop slip. The 2520 is a heavy boat, so expecting a single AL prop to give good performance without flex is probably asking too much.

The prop that I'm wearing now is a 15x17 Solas AL prop that has a more open exhaust port that the manufacturer claims yields a 5 to 10% increase in horsepower due to a less restricted exhaust. I cannot confirm an increase in power, but the exhaust tone is definately different and the hole shot is much improved.

This particular prop is the best I've used to-date, but I believe it is still a bit too much prop. Last year on flat water my boat saw 33 knots at 5100 rpm from my 1997 Yamaha 225 OX66 at WOT.

My thought is that a 15x15 stainless prop should probably put me closer to 5500 rpm at WOT which should be optimum for my motor. Trouble is, 15x15 stainless wheels aren't exactly a common size.

Like most people, I almost never run at WOT. Most of the time I run between 4000 and 4300 rpm at cruise, so whatever wheel I try this coming season has to continue to give me the same mid-range performance the 15x17 Solas is giving me now.

Tuning a boat with the perfect prop is indeed voodoo science.
Good luck in your quest!

 

[Sow&Pigs]

Thanks Kevin. More good info. The rocky shoreline around my area in CT is one reason to stay away from stainless props. I'd rather replace a prop than a lower unit.

I knew when I posed the question it was kind of like asking "which is prettier: blondes, brunettes or redheads?" Although, come to think of it, that's easy compared to prop selection... :twisted:

 

[B-Faithful]

Kevin, I have a 14.5x17 Merc Black max AL and 17" Mirage plus SS (I think the diameter is 14.5 or 14.75) for you to try this spring. BW23 on THT loaned me the Mirage plus but I hit the rev limiter with it and will most likely try a Merc Rev4 this year. My boat is lighter, narrower and a slightly shallower transom deadrise so the 14.5x17 may be your ticket with 2520mv.

If anyone is interested in the Mirage Plus, they guy I borrowed it from wants to sell it. It has not dings it at all. Not sure what he wants for it but I can send him a note if anyone is interested.

Here are the specs on Merc props (click on the icons):
http://www.mercurymarine.com/props

 

[Megabyte]

Hey Greg! I'll take you up on that.
See you tomorrow evening at Pussers!

 

[Elysium]

Realize this is an older thread but I wondered what the results were or if there is new thinking on the subject.I have a 1995 2520 MV with a transom mount and will be putting a 2007 Optimax 225 on early next month.
Not really too concerned about top end because anything will seem spooky fast after running the poor Saltwater 150 that it came with.Economy and decent mid range will be our main goal.Did put on Bennet 24x9 tabs this spring (had none) and already love what they do even on a very underpowered platform.
Thanks

 

[Megabyte]

A 17p Mercury Mirage Plus is what I run on my 1996 2520 MVSC.
Just came in from fishing, and on my typical WOT blast in the creek, she ran 32kts at 5100 rpm with 2 on board, 3/4 fuel, and all my fishing and safety gear.

I think a 16p would give me a few more RPM's on top, but I'm not certain they even make a 16p.
Of all the props I've tried, this one works the best (so far).

 

[Elysium]

What diameter does the Mirage 17P have? I assume it is 15 but I saw a 15.5 at an (almost) reasonable price-would that work as well?

 

[Megabyte]

Can't answer that, but if you search on the part number shown in the photo... you should find what you need.