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Hi All. I have a 15 ft Boston Whaler Dauntless that I just re-powered with 60 HP Evinrude E-Tec. I previously had a 75 HP Merc Mariner that powered my boat to 45 MPH. Due to the gas consumption and a limited range with the amount of gas I could carry I decided to drop down in HP to get more range and not having the need for the speed to Merc provided. It was just too fast.

Anyway the E-Tec came with a S/S 13 7/8 x 13 prop. The top speed with this prop was a disappointing 26 MPH @ 5300 rpm. It would not get up to the top RMP's for this motor which is 5600 RPM. I called the dealer and explained the problem to him about lack of top end speed. He recommended and sold me an aluminum 13 7/8 X 11 prop. I installed it and took it for a test drive and I was able to get to 5600 RPM, but my top end speed was only 20.2 mph. Way not acceptable. I have read on the forum when boats like mine and powered similarly get up to 33-35 MPH. I am totally frustrated. Any suggestions on how to get more top end speed? Should the dealer have sold me a 15 pitched prop instead of an 11? Help!!!!

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Mounting the correct propeller is somewhat complex. Dealer's are known for throwing a prop on a motor thinking in general terms. Actually it is a science and you have come to the right place.

While we wait for the prop guru's, let me pose a few questions.

What is the brand and size of propeller? Then again what you have is totally wrong.

To select the appropriate prop, the guru's will want to know at what height is the engine on the transom. Looking at the top engine bolts, how many empty holes are above the hole the bolt uses.

What is the typical load of people, fuel, gear and other items of weight (in lbs) that you will typically have on the boat.

Here is a thread discussing props for a different engine but similar model. While the prop recommendation made may not apply, it is a good read on how props are selected based on boat model, engine gear ratio etc.
http://www.whalercentral.com/forum/vi...rowstart=0

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Thanks for the response. The motor came with an Evinrude SSP stainless steel 13 3/4 three blade 13 pitched prop. The prop the dealer sold me to solve my issues is an Evinrude Hydrus three blade aluminum 13 7/8 11 pitched. The replacement prop actually made the problem way worse.

As far a motor mounting. There are four mounting holes. It is bolted to the transom through the bottom hole, so it could go down three holes if needed ("Three Holes Up"?) . The top hole is flush with the top edge of the transom.

o <-- bolts through this hole, motor mounted "All The Way Down"
o <-- "One Hole Up"
o <-- "Two Holes Up"
o <-- "Three Holes Up" (where it should be if using a good stainless steel prop) This is where it is mounted



Usual load is two people with fishing or crab gear. I have a 11 gallon tank and spare 2 gallon tank and a 4 HP Yami Kicker.

I do get quite a lot of bow rise when I take off until I get on plane. I plan on installing Smart Tabs to help solve that problem.

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Until you get the correct prop, do not install tabs yet. Some props have stern lifting properties and will reduce the bow rise.

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I'm by no means a "Prop God", but I do have a 15 Dauntless with a 60 Merc 2 stroke ( my prop thread linked in a previous post). I'm currently running a Stilletto 12 X11 pitch Stainless prop and routinely get about 33-35 mph WOT at about 5200 rpm. Pretty good hole shot, and have my motor in the next to the highest position (up 4 out of 5 holes). I've recently re-added the Dole Fin to the motor since It does make the hole shot even better, and stabilizes the steering at lower planning speeds.

In the future I may think about opting for a 4 blade prop since I still get some minor low rpm "prop rattle" with the big eared 3 blade Stilletto.

I'm really interested in this thread as the 60 E-tech was on my short list for a future repower of my 15 Dauntless. I just wonder if you actually may have the motor just one hole too high and so it's not getting enough "bite" once up on plane.

You are carrying more weight than I am. I've a 9 gal Moellner tank under the seat, no spare tank, and no kicker. Normal load is just me, my wife, 25 lbs of fishing tackle and lunch

Gary

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Question Blktailhunter, is your fuel tank located within the helm seat housing? Where is your battery located? If not in the center console you may want to consider this option.

There was an option of going to a larger plastic fuel tank that could fit in this housing if you needed more fuel for better range. I replaced the OEM fuel tank that my Dauntless came with for a larger Alcohol compliant unit from Moeller Marine.

What model year was the Mercury 75 that the Dauntless had? Weight difference compared to E-TEC 60?
Is the E-TEC a 2 cylinder? Does the E-TEC use an external 2 stroke oil reservoir or is it mounted directly on the power head?

What was your thought in choosing to go down on the horse power scale rather than up? An E-TEC 75 would have been more fuel efficient than the older Merc and had a bit more push for the Dauntless. Was there a big price difference between the 60 and 75 E-TEC?

I apologize for the off topic questions, was curious about the horse power selection. Regarding trim tabs, I would suggest holding off on this as one member already mentioned. My Dauntless 15 had them when I purchased it and I have yet to find a situation that warrants their use.

Not to familiar with the Smart Tabs, I only know that they are pre-loaded and react to the force or contact from water when attempting plane. Prop selection as has been mentioned is going to depend on your boat/outboard set-up, hopefully Tom Clark can offer some thoughts to your current prop dilemma. I am of the opinion that the 1994 thru 1998 Dauntless 15's should have been rated for horse power just a bit greater than a 75.

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The fuel tanks are both located under the helm seating. I have two batteries installed in the center console compartment. The Merc was a 1995 2-stroke 3 cylinder motor. I do not know what it weight, but it definitely weighted more than the E-Tec which is two cylinders and has the oil reservoir ( 1 qt ) mounted on the power head.

The reason I went down in HP is the 75 was just too much power for my boat. 43-45MPH top end speed. Even at lower speeds it really sucked up the gas. My first choice was a 70 HP E-tec, but that motor was discontinued. That let me with either a 60 or 75 HP. I had read in these forums somewhere where a boat like mine and powered with a 60 horse motor would get up to 33-35 MPH. That was exactly where I wanted to be. Enough speed and a smaller motor which would use less fuel and increase my range. Or so I thought.

Now I have two props. One gets up to 28 MPH but also only gets a max 5200 RPM. The motor is rated at 60hp @ 5600 RPM. The other prop, the 11 pitch, allows me to get my 5600 RPM's but has a max top end speed of a paltry 20.2 MPH.

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Wow, it seam you have a small dilemma...

The Dauntless 15 (if memory serves correct) was rated up to 75 hp. The Dauntless 15 is not a real heavy hull but it's certainly not a feather weight either.

My feelings are that the E-Tec 60 as fuel efficient as it is may be may also not be "torquey" enough to push the Dauntless to a comfortable speed without some strain.

I think some of those Dauntless's mentioned with a 60 hp where actual 3 cylinder models (other and older makes) like your previous Mercury 75. 3 cylinders versus 2, a bit more torque with the 3. Has Tom Clark posted any prop info for you. There may also not be a varied selection or rather prop options for that size E-Tec that will compliment the Dauntless and your needs?

Even Yamaha's (when available) 50 2 stroke was a 3 cylinder the "Back Country" or "Flats" guys down here love those small outboards for there reliability and efficiency.

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I suspect there is something going on here that is more than just the prop.

If I look at the e-tech boat performance reviews on the Evinrude site, I see performance figures for heavier boats that are consistantly in the low 30 mph range. Almost all of these are using the 13 1/2 X 15 prop. Most have more than 5 seconds to plane, which I consider less than optimal, but the top speeds are about where the OP wanted to be. Also, most seem to have the motor mounted in the "#1" hole (whatever this means).

This performance review of the Triumph 170 CC with an E-tech 60 hp would be what I would expect as minimal performance for that motor on the Dauntless 15, the Dauntless having 250 lbs less dry weight.

http://www.evinrude.com/Content/Pdf/n.../PE870.pdf

BTW, Yesterday, WOT speed on my 1998 15 Dauntless was 33.5 mph (gps) at 5100 rpm with my 1998 60 Merc, the 12X11 Stiletto prop, and Dole Fin. This is down 1 mph and down 100 rpms after adding the Dole Fin, but time to plane is 3 secs. with 2 people and normal fishing gear/fuel.

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Thanks for that link. I noticed that in that test they used an aluminum 13 1/3 x 15 prop. I'm thing that maybe that dealer should have sold me a 15 pitch prop instead of that 11 pitch. That might be the solution.

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OK........

Not sure how this actually works out, but the performance difference between your 11 pitch prop and my 11 pitch prop may be due to the gear ratios of the lower units.

My Merc has a ratio of 1.64/1 so with my engine rpm's at 5200. I'm turning my prop at rpm of 3292 (hope I'm right on this). Your E-tec has a gear ratio of 2.67 so at engine rpm of 5600 you are only turning the prop at 2092, about 2/3 of my prop rpm's. It's most likely not a true comparison, but 2/3 of my 33 mph boat speed is your 22.

Hope somebody that knows WAY more than I do chimes in to set me straight.

Gary

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Just got off the phone with the dealer. He's thinking it is not a prop problem. He thinks it might be a exhaust buffer baffle( I think that is what he called it) issue? He is going to have the tech check the motor out and order new parts if that is indeed the problem. They will be giving me full refund for the aluminum prop. It's the middle of salmon season so I won't be taking the motor in for a couple of months.