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  Dauntless 16. Yam F115. performance

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Author Topic:   Dauntless 16. Yam F115. performance
John Lay posted 06-01-2003 05:28 AM ET (US)   Profile for John Lay   Send Email to John Lay  
Any thoughts please on this rig running a Rapture 13.25 x 17 prop. 5800 WOT. Load is full tank, two people (400lbs!).G.P.S is registering a max. speed of 41.7 M.P.H with an ave. 40.5 although "speedo" registers 45 M.P.H. My figures seem a bit low compared with some on the forum or are speeds quoted often taken from an optomistic "speedo"? The original Yam. 19 Pitch black ss prop. revved to 5700 WOT gained 1 M.P.H but wasn't as responsive for skiing. Any ideas appreciated.
Perry posted 06-01-2003 12:58 PM ET (US)     Profile for Perry  Send Email to Perry     
41.7 mph seems a little slow for a 115. I imagine with less gas and just you, you'll pick up a couple of mph. I have the same boat (2002) with a Honda 90 and it tops out at 40.1 @ 6000 rpm with 13.25 x 16 ss prop and a light load. I gained a couple of mph by raising my motor 2 holes. What year is your boat and motor?
John Lay posted 06-01-2003 06:13 PM ET (US)     Profile for John Lay  Send Email to John Lay     
Thanks thats helpful.I bought the rig new in 2000.It's fitted with a Doel fin but no trim tabs.Although if trimmed right up it'll rev. to 6000 it's most comfortable around 56/57 above this it starts to porpoise unless flat calm.I'll check the engine position but perhaps nudging it up 1 or 2 holes might help? Normal load is 50lbs of anchors & chain in the front locker & approx. 50 lbs in the console.
Perry posted 06-01-2003 06:46 PM ET (US)     Profile for Perry  Send Email to Perry     
Your boat has the notched transom which I've been told ads to the porpoising effect. Is the Doel-fin touching the surface of the water at WOT with the motor trimmed out? Doel-fins can rob a few mph if they are dragging at WOT. Raising the motor may help in your application.
John Lay posted 06-01-2003 07:02 PM ET (US)     Profile for John Lay  Send Email to John Lay     
Thanks I'll check that out.
Marlin posted 06-01-2003 09:42 PM ET (US)     Profile for Marlin  Send Email to Marlin     
I just finished my initial break-in on a 2003 160 Dauntless with a 115 Merc 4-stroke. I've only run WOT very briefly, but I agree with Perry that your numbers seem low. I have a Vengeance 13 (maybe 13.25?) x 19, and at 6000 RPM, my GPS wavered around 42-44 MPH with 2 people, big dog, 7/8 tank, bimini up. I'm looking to swap to a 21" pitch, since I have to back off to keep it to 6000, and that should bump the top end up just a little more. My ventilation plate is also just about even with the hull bottom, so maybe I need to come up a hole. It runs underwater at 3500, but I haven't gotten a good look at higher speeds. Tweak, tweak...

The 2003 hull does not have the transom notch, nonetheless it does ride with a somewhat bow-up attitude compared to an old Montauk (16/17 hull) and coming on and off plane is more pronounced. More down trim authority would be nice. The boat also seems extremely sensitive to trim settings as I change power; perhaps this is typical, but this is my first outboard above 10 HP. Once trimmed, the ride is delightful and steady as a rock. And very, very dry.

John Lay posted 06-03-2003 07:25 PM ET (US)     Profile for John Lay  Send Email to John Lay     
Just checked out the Doel Fin position at planing speed and it's dragging underwater. Trimming up so that it's skimming the surface and I'm porpoising at 6000 R.P.M. Engine is mounted on the top hole, presumably I need to move it "down" 1 or 2 holes which effectively moves the engine up 1 or 2? I presume by doing this, Revs. will rise,less porpoising and a bit higher top end. Or is that too good to be true?
Hugh Williams posted 06-03-2003 07:43 PM ET (US)     Profile for Hugh Williams  Send Email to Hugh Williams     
I have the 99' 16 Dauntless with a 90 hp. the top speed i have ever seen is 43mph on gps but has decreased to 37 at 5200 rpm with a max of 5500 when i changed to a 4 blade for sking. I would like to add trim tabs to lower my bow and still be able to have the faster prop. I also have a dole fin on, and it is out of the water trimmed all the way up at wot. I want to know if raising my motor up a notch or 2 will help even more.
lhg posted 06-03-2003 08:40 PM ET (US)     Profile for lhg    
Marlin - recommend you lift the engine one bolt hole and use a 20" Mercury Laser II prop. It will run the same RPMS as a 21" Vengeance, but give you superior performance and holding.
Marlin posted 06-04-2003 09:56 PM ET (US)     Profile for Marlin  Send Email to Marlin     
lhg, thanks for your advice. My dealer wants me to put some more hours on the engine, then do some longer WOT runs to get a better picture of the performance. They've agreed in principle to swap props if that's called for. I'm a little bit lost on the nuances of one prop type vs. another, and in particular I'm wondering whether I really want a "bow lift" prop on this boat, given the relatively bow-high attitude that seems to be characteristic of the 160 Dauntless. The Mercury website isn't all that enlightening on different prop types, and their prop selector applet gives answers that are all over the place.

Thanks again,

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