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Have a 15 ft dauntless w/70 hp 4 stroke yamaha. Has a 13 1/2x 15 alum. Prop. Takes a while to get on a plane and starts to porpoise when starting to trim out. What would cause this? Have the motor up two holes out of three on transom. Want to avoid putting tabs on it any help out there??

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There should be 4 bolt holes on the top of the motor bracket. (maybe 5)

Which hole from the top does the bolt go through?
http://www.whalercentral.com/articles...cle_id=106

You already have an ongoing thread with replies in your other post here:
http://www.whalercentral.com/forum/vi...d_id=19086

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I have a 15 Dauntless with a Merc 60 2 stroke. I went to an 11 pitch stainless prop and that helped with both the hole shot, now less than 3 seconds, and the propoising. I also have a Dole fin that helps, too. Top GPS speed is about 34mph, which is OK with me. All that said, the Dauntless 15 still remains tender to the trim. Adding a body or 2 up front helps a lot., but 4 on my Dauntless is pretty crowded.

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google lifting props or props that lift. Even a small 4 blade prop might be the trick. I know you said no tabs but tabs or smart tabs might be the alternitive. You may need something to extend the running surface of the boat. and find a way to move as much weight forward as you can.

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Sorry guys, did have another thread going but could not get to it. Thought someone deleted it. But anyway, someone did suggest a dolfin but cant seem to get over the look when its on the trailer. Would a 4" jack plate center the boat out a little better?? When i finish tinkering with it, ill post some picts for suggestions. Thank you all

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Other post is now locked as it is not necessary to have the same question twice from the same person which gets confusing for most all of us.

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Yep, tell me about it. I hate having to rely on a hydrafoil/dolfin to keep mine from porpoising, but if I want to be able to use it, I had to attach one. Take it from someone who has resigned to the fact that my hull has some sort of "rocker" in it now and that some sort of action will need to be taken. You can spend valuable time moving batteries and fuel cells around in the boat to no avail or you can go right to the problem and, like bake said put a set of smart tabs on it and be done. I would put a set on my boat but my house is getting every extra dollar I have.

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Hello Fire Dragon and a question, how far above the keel center-line is your outboards cavitation plate?

If your motor sits low on the transom then the Aluminum prop will suffice but, if mounted all up or where your cavitation plate sits anywhere from 1 to 1-1/4 and even 1- 3/8 of an inch above the keel then a stainless prop should be considered.

The Dauntless 15 from my own experience is extremely senitive too to much positive trim. Trim tabs if hydraulic or electric may not be as efficient as you may think. Due to the length of the hull and its narrow beam along with ever changing water conditions properly adjusting the tabs to avoid porpoising may be more frustating than practical. I have Bennett hydraulic tabs on my Dauntless 15 and have adjusted them very very few times. The hull reacts to quickly to the tab input which could make for an "interesting" boat ride.

I have been testing a few different pre-set positions with my tabs for the sole purpose of generating a bit longer running surface when getting on plane but without affecting the ride attitude of the bow. Also I have changed to a different stainless prop modeled after Yamaha's "semi-cleaver" style which is suppose to offer improved stern lift capabilities. Its manufactured by Power Tech it a 13" Dia. x 17" pitch but I am still in the testing phase with the prop.

Hope the bit of info can be useful to you...happy boating
Angel M.

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I understand the reluctance on the fin. I took mine off, but finally put it back on and have grown to ignore the look on the trailer. In the water I don't see it, nor does anyone else. I have noticed that s great many of the smaller boats in my area have the Dolfin or other fin. Short boats need help.

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Since the Yamaha 70 has a "Bigfoot" gear case, prop choices are limited at such a low HP rating.

If price is an issue, I believe the Mercury 3 blade Black Max and 4 blade aluminum Spitfire are the best aluminum props on the market, and should be considered, at only $149-$159. Boston Whaler shows 150 Super Sport performance of 36 MPH with a Merc 60 Bigfoot and a Black Max aluminum prop. Not bad results at all.

For this Dauntless, the brand new design 4 blade Spitfire should be looked at, for only $159 complete with hub kit, to your door.

http://www.mercurymarine.com/propelle.../spitfire/

See jacosmarine.com to purchase.

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Good information on the aluminum 4 blade... that is the direction i would try for sure.

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Porpoising can be exacerbated by weight in the stern. A Yamaha 70 hp 4 stroke motor is not light.

While one can play with a foil or tabs, it is recommended to review the weight distribution in the boat. While your options are limited on a Dauntless 15, a review is warranted never the less.

One way to see the effect of weight balance is to have a passenger in the bow and go from a standing start to a cruising speed.