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Prop characteristics
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| gary0319 |
Posted on 02/05/13 - 6:18 PM
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I'm in the process of selecting a stainless prop for my 1998 Daunless 15 with a 1998 Merc 60 2 stroke (not Bigfoot). I'm not certain of the make/pitch of the current aluminum prop since I have not pulled it, and there are no external markings. I currently experience 31 MPH WOT at 5100 rpm, slight trim out. Hole shot is OK, cruises well at 22mph at 3800 rpm. 2 adults (about 300 lbs), 9 gals fuel, standard gear and fishing tackle. The motor has a dole fin. I'm thinking a 10.5 (+/-) X 12 pitch would be a good starting point.
Now the question....
I've read that some props have design characteristics to give "bow rise" and presumably some to provide stern lift. I certainly don't want any more bow rise as the Dauntless is suseptable to propoise if trimmed out to far, particularly into the wind in a chop. Of the following props on my short list, does anyone know which one would provide the least bow rise (and hopefully some stern lift)
Quicksilver Silverado
Michigan Wheel Apollo
Stiletto Triad II
Solas New Saturn
If there are any others that would more suitable, I'm open to all suggestions.
Gary
1998 Dauntless 15 - 1998 Mercury 60 |
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| Finnegan |
Posted on 02/05/13 - 10:25 PM
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I strongly recommend you stay with Mercury manufactured props. They are the biggest sellers in the world, perform best for their stated purpose, and hold their re-sale value best.
Since your boat is not all that fast, you don't need a performance oriented, high rake propeller. I would stay with the Mercury Vengeance or Quicksilver/Silverado. (same prop)
If you want to venture into more money and try to get a little better perfromance, they make a Trophy Sport model for the small gearcase that you could try.
I would also get rid of the Doel fin, as they tend to be speed killers. The engine should be installed in the second set of holes on the engine bracket, or so that the Anti-ventilation plate is running just clear of the water when on plane. If two holes up are needed, do that.
Edited by Finnegan on 02/05/13 - 10:51 PM |
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| gary0319 |
Posted on 02/06/13 - 5:34 AM
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Thanks, Finnegan,
Quicksilver remains at the top of the list.
Motor is mounted in the middle holes (3 of 5) and the cav plate is about even with the keel. See some detail pics on my personal page that I uploaded yesterday.
Also, I'm less concerned about loosing some top end speed than I am about getting up on plane, hense the dole fins. A lot of the area that I visit around the Sarasota Bay is speed limited because of Manatees or other reasons. 25mph is not uncommon. Top end of around 30mph is fine with me.
Thanks for your insight.
Gary
1998 Dauntless 15 - 1998 Mercury 60 |
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| Tom W Clark |
Posted on 02/06/13 - 6:07 AM
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Gary -- All four of the propellers you have listed are comparable to one another. There is nothing special or better about the Mercury Vengeance/Quicksilver Silverado, in fact it is one of the worst propeller models Mercury makes.
As you have found, the motor mounting position on the Dauntless 15 is a little different from other models and a "One Hole Up" position, as Larry (Finnegan) suggests, would be w a y too low. I recommend you move the motor up one more hole to the "Three Holes Up" position.
The Dauntless models tend to suffer a lot of bow rise on acceleration and can porpoise if the motor is too low and the propeller does not provide much stern lift.
Propellers with a lot of blade rake and small diameters tend to contribute to bow lift. Props with low rake and larger diameters and more blade area contribute stern lift which is what you want.
Going to a four blade propeller is one way to increase blade area, but a better solution in your situation would be to try a large blade area three blade prop like the Stiletto Star 3.5, which was originally designed for pontoon boats but has proven to be excellent on many small skiffs, flats boats and even the Outrage 18 equipped with some small gearcase motors. It is also quite inexpensive.
For your Dauntless 15 and its 60 HP Mercury two stroke, you would want the 12" x 12" size with a C-011 Guardian hub kit.
The combination of the motor being raised one more bolt hole and a new Star will have a profound effect on your boat's performance.
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| gary0319 |
Posted on 02/06/13 - 8:20 AM
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Thanks Tom,
I'm still confused a bit by the "how many holes up" lingo that all use here. My motor is currently in the middle holes of the 5 avialable. I'm assuming this is "2 holes up", and you are recommending it go one hole higher, right?
Thanks for the insight on the Stilleto Star 12x12.
Gary
1998 Dauntless 15 - 1998 Mercury 60 |
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| Tom W Clark |
Posted on 02/06/13 - 8:45 AM
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Maybe this pictogram of the bolt holes in your motor's mounting bracket will help with the lingo.
o <-- bolts through this hole, motor mounted "All The Way Down"
o <-- "One Hole Up"
o <-- "Two Holes Up" (where it is now)
o <-- "Three Holes Up" (where it should be if using a good stainless steel prop)
o <-- "Four Holes Up"
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| gary0319 |
Posted on 02/06/13 - 8:48 AM
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As they say, a picture is worth many words,
Thanks
1998 Dauntless 15 - 1998 Mercury 60 |
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| Tom W Clark |
Posted on 02/06/13 - 8:58 AM
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I'm going to take back the 12" pitch recommendation. I think you should try the 12" x 11" Star 3.5.
You can also try to find a used or older Star, know as the Star I which has a press-in rubber hub. Some vendors still have old stock but others have new stock but use the old model name. Yes, it gets confusing.
If an older version of the Star, it is a Star I, part # 12011 for the 12" x 11" size
If the current model with field-replaceable hub kit, it is part # C 802211 w/ the aforementioned C-011 hub kit.
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| gary0319 |
Posted on 02/06/13 - 9:36 AM
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Tom,
I've done some searches on the Star series and found some had Star I and some had Star II only (and only in larger sizes ). Is there a hub or some other advantage to the Star II
Now I'm not sure this is allowed, but could anyone give me a recommendation on which on line dealer would be both low price and reputable? I read some stories of non delivery problems, etc.
Seems to be about a $100 or more range in prices........but I don't want to be price-foolish about this. PM me if this is a sensitive issue.
Gary
Edited by gary0319 on 02/06/13 - 9:39 AM
1998 Dauntless 15 - 1998 Mercury 60 |
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| Finnegan |
Posted on 02/06/13 - 12:10 PM
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You will have a hard time beating these prices on Mercury props, which include shipping and no sales tax. I have bought from them, and they are legit. On most lines they actually beat the web discounters on the Mercury Quicksilver props.
http://jacosmarine.com/new_mercury_pr...r_sale.cfm
They show $119 for an aluminum, and $250 for the 4 blade Trophy Sport or Vengeance. The price on that Sport is a bargain, and that is what I would buy if you are mounting high on the transom.
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| Tom W Clark |
Posted on 02/06/13 - 2:15 PM
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Gary,
Star I is for small gearcase outboards (3.5" hub) like yours.
Star II is for intermediate size gearcases (4.25")
The current model names are Star 3.5 & Star 4.25
Many vendors still use the old I and II designation even though they are selling the newer models.
The only difference between the new and old versions is the hub.
I and II use a press-in rubber hub specific to the brand of outboard.
Star 3.5 & Star 4.25 use the field-replaceable Guardian hub kits which allows a single propeller casting to be used with anybody's outboards so long as you use the right hub kit.
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| gary0319 |
Posted on 02/18/13 - 1:32 PM
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Today was the first trial for the new prop, a Stiletto Star Stainless 12X11 pitch. Thanks to Tom W. Clark for taking the time to explain to me the ins an outs of selecting a propeller to get the desired results.
To recap, my 1998 Dauntless with a 1998 Mec 60 2 stroke was tender to the trim and needed to be kept at about 21 mph to keep from falling off plane in a chop. I wanted to be able to hold plane at a lower speed and not be afraid of introducing propoising when trimming up, particularly into a wind. Tom suggested replacing my 10.5 X 12 aluminum with the Stiletto 12X11 Stainless. See my personal page for this beauty
The results were beyond good. Today's conditions were moderate chop with wind about 12, just bordering on whitecaps on Sarasota Bay. The first surprise was that the old feeling of "digging out of a hole" was gone, even with less than full throttle. The little Dauntless just seemed to "lift" itself up on plane. No big bow wave to climb over. Next was WOT downwind.....34.5 mph at 5200 rpm with moderate trimming. Return leg into the wind served up 31.5 mph at 5100 with slight trim. The old aluminum 10.5 x 12 only produced 31mph at 5100, at best. I think once I get over still being "trim shy" I be able to coax a few more MPH and RPMs, particularly in flat seas.
The best of the best, however, was being able to hold plane at 17 mph even in the chop.
Tom , you are the Man!!
Edited by gary0319 on 02/18/13 - 2:06 PM
1998 Dauntless 15 - 1998 Mercury 60 |
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| Tom W Clark |
Posted on 02/18/13 - 7:52 PM
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Gary -- I am glad you have found some improved performance with your new propeller. Have you raised the motor on your transom yet? If not, there is more performance yet to come.
Unfortunately, Mercury has no propeller to compete with the Star, at any price. It sounds like you spent $200 very well.
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| gary0319 |
Posted on 02/19/13 - 4:23 AM
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Tom,
You are right. Best $200 I've spent in a while...
Feels like a whole new boat.
I haven't raised the motor, one change at a time. I'll run it this way for a while and then decide if I want to lift the motor.
Gary
1998 Dauntless 15 - 1998 Mercury 60 |
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| Tom W Clark |
Posted on 02/19/13 - 7:48 AM
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When choosing a propeller, there is often too much focus on top speed, probably because it is easy to measure and it needs to be measured during the prop fitting process, but top speed is ultimately, something that is really not very important to most of us.
When you get a prop that really works well, the whole boat often just seems to be different and better. "Feels like a whole new boat" is a frequent comment, and the most satisfying for me. This is, after all, our goal here and it justifies these sometimes tedious and technical discussions.
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| gary0319 |
Posted on 02/19/13 - 2:00 PM
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Tom W Clark wrote:
When choosing a propeller, there is often too much focus on top speed, probably because it is easy to measure and it needs to be measured during the prop fitting process, but top speed is ultimately, something that is really not very important to most of us.
When you get a prop that really works well, the whole boat often just seems to be different and better. "Feels like a whole new boat" is a frequent comment, and the most satisfying for me. This is, after all, our goal here and it justifies these sometimes tedious and technical discussions.
Right on........top speed was the least of my concerns, but being comfortable with how the boat performs at my normal (or desired) operating speed was what I was after. The fact that once the boat was more balanced with the correct prop, the top speed actually increased, was just icing on the cake. Today, based on Tom's advice I gave the prop nut another crank to issure the hub was seated. Got about a third of a turn out of it. Good to go........
1998 Dauntless 15 - 1998 Mercury 60 |
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| gbollin |
Posted on 03/12/13 - 9:41 PM
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Sorry for the late question: I also have a 1997 Dauntless 15, planning to repower with a 60 hp Merc 4 stroke (not a big foot). Would the same prop be appropriate for this engine? Thanks.
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| Finnegan |
Posted on 03/12/13 - 10:46 PM
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I would go to the Prop Selector software on MercuryMarine.com and plug in your information. See what they recommend in both sytle and pitch.
The 4-stroke 60 may have different gear ratios and RPM limits than the older 2-stroke 60.
I would also check Whaler.com for performance reports on new similarly sized whalers using this engine. See what they are using. It may not be exact for your model, but should give you some close ideas.
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| Tom W Clark |
Posted on 03/13/13 - 8:51 AM
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The Mercury FourStroke 60 has a 5500-6000 RPM range and a 1.83:1 gear ratio, so yes, it could make use of the same propeller.
The trouble with using the Mercury Prop Selector is that it (obviously) only spits out Mercury propeller recommendations and Mercury just does not offer much at all. It's the old Vengeance 3 blade or the Trophy Sport 4 blade; that's it for their 3.5" stainless steel propellers.
I actually think the Mercury 60 BigFoot would be a better motor choice for a Dauntless 15 because it uses a much lower 2.33:1 gear ratio and can use the 4.25" class propellers so you get more blade area from whatever propeller model you select.
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| gbollin |
Posted on 03/13/13 - 7:27 PM
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Thanks for responding. Please bear with my novice-level questions. I don't understand gear ratios and lower unit size and how they affect prop size. Also, the big foot is heavier and extends lower into the water-wouldn't these factors tend to aggravate the tendency for porpoising compared to the standard engine? Can you tell me if any of the newer aluminum props would perform similar to the stainless props, or give me a reference to read about these?
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