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B-Faithful

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Is anyone running a 4 blade prop on their pilothouse with a single outboard? If so, what were your thoughts?

I just ordered a 4 blade stainless steal prop (Revolution 4) in hopes of getting more bite in rougher water and reducing prop slip at cruising speed. The Rev 4 is the only prop the merc prop selector program noted as an appropriate prop for ALL performance goals for a cuddy cabin boat weighing 5500-6000lbs loaded. I am just hoping I made the right choice after putting out the dough.
 

DaleH

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Props ... they're not rocket science ... they're much WORSE than that!

I tried a premium SS 4-blade on my Parker, but one which admittedly, said would raise the bow. It did that soooooooooooo much that I had to deploy my trim tabs much more than usual. And my usual tab position improves[/b] my fuel efficiency +10% over no tabs ... but in this case, I lost 10% from normal, which meant a 20% loss in MPG @ cruise speed.

That does NOT mean that will happen with your boat. But picking props can be like selecting a girlfriend or a wife ... youse makes the best choice you can, but in the end ... only time will tell if you made the right choice.

Oh yeah ... and both end up costing you $$ ;) !
 

tara11

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On my 2301 Striper I just sold I had a 4 blade SS prop and it worked great, less vibration and seemed to run smoother !
I have 4 props for sale and they are all really good props, two came ofrf a Yamaha 225 S Steel and one came off a 135 Optimax !
 

B-Faithful

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Thanks for the feed back. This rev4 is supposed to give transom lift. I am not sure I need too much of that with my boat as I only have 10 degrees of deadrise and she planes very easily. It should help in getting the bow down in slop though. The dealer said to either go rev 4 or mirage plus. I went rev 4 because I am hoping to reduce slip with more surface area. We will see. I do have a used Mirage to test to compare to the rev 4. I think Megabyte is going to test the Mirage Plus 17" on his boat once he gets it back.

What pitch and diameter do you mv2520 guys run with 225 outboards (I know gear ratio plays a roll but am curious)
 

DaleH

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B-Faithful":1z8yymla said:
What pitch and diameter do you mv2520 guys run with 225 outboards (I know gear ratio plays a roll but am curious)
15" x 17" 3-blade @ 1:86 ratio
 

Megabyte

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Greg... 15x17 is what my dealer tells me is ideal for my boat, but I have that prop on my boat now and she would only do 5000 rpm @ WOT on flat water last year.

My boat is a bit heavier than the typical 2520 because (I believe) of the three fuel tanks.
Last year I would run 5000 rpm @ 33 kts WOT on flat water, but I'd rather be running 5500 rpm...

So... I'd like to try that 14.5x17 (I think it is) and see how it runs.
FWIW... I really like the prop that I have now. It gives great bite in the low range, and the mid-range... I just wish I could get a few more revs out of her.

On a side note... I am replacing the three (1997 vintage) fuel pumps this spring, in the hope that I might find that extra 500 rpm.
Report to come later this spring.... :wink:
 

Ranger Tim

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Megabyte,

Maybe we need to have a prop testing raft-up : ) It would be fantastic to be able to wade and change props for test runs. Have you tried a 15-1/4 X 15 Black Steel?

edited to correct prop size.
 

Megabyte

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Ranger Tim":staa1f4k said:
Megabyte,
Have you tried a 15-3/4 X 15 Black Steel?
I have not... But I have thought that a 15x15 stainless wheel just might be the right wheel for me. :)
I'd love to try something in the range...
 

susqking

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Kevin,
I have a Yam. 15 1/4 x 15 M you could try, before you go buy one. The guy I bought the boat from put it on and I keep it for a spare. I run the 15 1/4 x 17 SWS.

You will definetly gain some rpm's with it.

Anthony
 

B-Faithful

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Ok. I ran my 17" Revolution 4 today and the performance is impressive compared to my old prop. I didn't notice a better whole shot (if anything slightly worse-not that I gun-it either) but my prop slip is greatly reduced at cruising and I couldn't get it to ventilate no matter how I trimmed the motor. At 3980 I was running 28.3 mph into a light wind burning about 10.2gph with 2 adults, 2 kids and around 120 gal of fuel (ran just under 30mph at around 4060 burning 10.6gph). I previously had a 17" Black max AL prop that would go all the way to the rev limiter of 5750. It would run about 26-27mph (closer to 26 when the bottom was painted) at 4000 rpms burning just under 10gph and would ventilate on occassion when not trimmed properly. I also would have to turn a solid 4200rpm for a good 28mph. My problem is that the max rpm I would hit with the Rev 4 was right around 5400rpms. I am concerned that this is too low despite my manual recommending 5000-5750. I did hit around 41mph and think if I fooled with the trim more and had more room in my creek, it would have gone higher. I was only hit 39.8mph without bottom paint with the black max. My hull is different than most boats being that the faster I go, the more the bow goes down due to the sharp entry and 10 degree of deadrise transom. This obviously makes for a longer running surface creating more drag. Regardless of trimming the engine up, the bow doesn't really react because of the flatter transom and forward weight of the pilothouse. I personally don't care about running WOT but do care about running around 3800-4200 rpms as that is where I cruise.

Being able to only reach around 5400rpm, Do you think I am over propped or does it sound about right? The only thing missing for a full load was some rods, ice, and tackle.
 

John_Madison CT

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B-Faithful: You are overpropped if you're only hitting 5400RPM's @ WOT for that engine. That explains why you're getting more speed for a given RPM. It appears like a gain, but in reality, it isn't since your lugging the engine.

John
 

B-Faithful

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Thanks john (not really... spent 450 on the prop :oops: ). I am going to go out when I have some time and fool with the trim to see how she does before casting her off. The runs were short as I had my 6 month pregnant wife on the boat and was only allowed to open her up in the short distance of my protected creek. My MPG's got better with this prop and it really "bites" the water on plane but dont want to lug the engine either. I understand lugging an engine leads to carbon build up and shortened engine life...

Thanks again.
 

Megabyte

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I don't care what 'they' say on THT. 5400 rpm isn't exactly lugging her.
You're only 300 rpm from topping that motor out.

But, if it is still a concern, underprop her a bit like she was before and run a few more revs during the 'normal' times when the Bay is chopped up. After all... how often do we see the Bay flat? It's not that often that we get to run in the upper rpm range anyway. :)

But... what do I know? I haven't dialed in my prop yet either. :roll:
 

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