160 Dauntless Re-power Mercury 115 FOURSTROKE

Optimizing the performance of Boston Whaler boats
gmaster
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160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby gmaster » Wed Jan 23, 2019 2:46 pm

I have to decided to re-power my 160 DAUNTLESS with the new Mercury 115 FOURSTROKE which is only 10-lbs heavier than my current engine. Based on the 2.1-liter displacement [the Mercury 115 FOURSTROKE engine] should have plenty of low end torque which is helpful on this stern heavy boat. The new 170 Dauntless uses the 115 Command Thrust 115 with an ENERTIA propeller, which is the [choice of gear case and propeller] I want. The local Mercury dealer has a Mercury 115 with the regular gearcase in stock, and [his price to me for that engine is] much cheaper than trying to order a Command Thrust gearbox engine.

To anyone with an opinion: How important will the Command Thrust gearbox be for this boat?

Will the regular gearbox 115 do the trick?

BACKSTORY: I have a 2004 Dauntless 160 which I have had since it was new. It has a 115-HP two-stroke-power-cycle outboard engine with carburetors which weighs 348-lbs. It has been a good performer with lots of low-end torque to get the boat on plane. However, it is having [problems]. The engine has always been a pain to start. And it idles and trolls roughly.

Bryan

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GoldenDaze
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby GoldenDaze » Thu Jan 24, 2019 1:52 pm

I have a 2003 Dauntless 160 with the original 2003 115 four-stroke-power-cycle engine. My engine has the same 2.07:1 gear ratio as the current 2019 Mercury 115 FOURSTROKE, and a reasonably similar RPM limit. (I believe mine is 6200, while the web page for the current engine says "5000-6000"). I have had excellent success with a 17-pitchTrophy Plus propeller, see http://continuouswave.com/ubb/Forum4/HTML/004868.html for details (that's me, at the time my username was "Marlin").

I would not hesitate to buy the 115 FOURSTROKE with the normal lower unit instead of the Command Thrust version. And the 17-pitch Trophy Plus would probably be a great propeller to start with.

-Bob
Last edited by GoldenDaze on Fri Jan 25, 2019 3:11 pm, edited 1 time in total.
2003 160 Dauntless Golden Daze

Jefecinco
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby Jefecinco » Fri Jan 25, 2019 10:02 am

Bob - That Dauntless 130 must fly with a 115 HP engine. What's your speed at WOT? ;=)
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GoldenDaze
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby GoldenDaze » Fri Jan 25, 2019 3:11 pm

Haha, 130, 160, whatever! It's all just numbers! Corrected previous post.
2003 160 Dauntless Golden Daze

gmaster
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby gmaster » Sat Jan 26, 2019 5:54 pm

If I do purchase the regular gear cased Mercury 115, I may just start with my propeller from my old engine, a Michigan Rapture 13.25 x 17-pitch. That propeller was perfect with the 115-HP two-stroke-power-cycle engine with a anti-ventilation plate foil appendage and the engine mounted one-hole-up from lowest.

Bob's propeller choice--17-pitch TROPHYplus--makes a lot of sense.

Bob's advice in 2004 after I first bought the boat helped me to set the boat up correctly by adding the [anti-ventilation plate foil appendage], raising the engine mounting height to one-hole-up , and picking the RAPTURE propeller.

Also, I have been gone for a while from continuous wave but I am glad to see Bob and his Dauntless 160 still have a big presence here.

I am also planning to add the hydraulic steering while I am changing out the engine.

Bryan

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GoldenDaze
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby GoldenDaze » Sun Jan 27, 2019 7:09 pm

Hey Bryan--if that's the propeller you have, then I'd certainly give it a go first.

On the hydraulic steering, I posted an article about my upgrade at http://continuouswave.com/forum/viewtopic.php?f=6&t=3456&p=20810.

Now I have a new favorite upgrade, replacing the hydrofoil with trim tabs. Amazing difference to the boat!

http://continuouswave.com/forum/viewtopic.php?f=6&t=3860&p=21744#p21744

There's always something else to do and something else to spend money on, right?

-Bob
Last edited by GoldenDaze on Mon Jan 28, 2019 12:03 pm, edited 1 time in total.
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby jimh » Mon Jan 28, 2019 8:50 am

BOB--the two articles you wrote are both excellent sources of information and very nicely supported with illustrations. They are great additions to the website, and thanks, again, for your contributions.

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GoldenDaze
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby GoldenDaze » Mon Jan 28, 2019 12:04 pm

Thank you Jim! Just trying to give back a little for all that I've learned here over the past 15 years.
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Lupi
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby Lupi » Wed Jan 30, 2019 4:09 am

Hey Brian,

I will certainly, in the coming years, have to change my engine as well. Same boat as yours (but from 1999, with notch in the hull) and I have the 90 HP 2 stroke mercury (same family as your 115) and my current prop is a Stlitto 13 1/4*17 pitch, so same profile and specs as your Michigan . I'm also looking @ the current offer in 115 4 stroke in the Mercury range and would like to re-use my prop (if possible)

I understand your question about re-using your Michigan prop on the small gearcase 115 4S Mercury.

Your current engine has a max rpm between 4750-5250 with a gear case ratio of 2.07
The new Mercury has max rpm between 5000-6000 with same gear ratio of 2.07

The new Mercury is turning @ higher rpm with same gear ratio. If you were happy with your current 115, I remember in an old post, you reported 45-46 mph @ 5000 rpm, then, in theory, I would tend to think that the Michigan prop 17 is a bit too much pitch for this engine... But that is theory... I know that in real life (new engine, different mounting height maybe, etc...), things are sometimes different, reason why, I woud try this prop as well...

This new Mercury weighs roughly the same as your current 115, that is a good new given weight sensitivity on this boat. Regarding mounting height, I would go to 3 holes up if your Michigan is OK with that setting (and I'm sure it is)

0
0
0
0-->3 holes up
0

Repowering this particular boat today is a challenge given the offer on the market with 4 stroke engines that weigh too much. Mercury is the lightest offer in that power range. I'd be interested to hear your experience once you have changed for this new 115 hp.

Brgds from France

Luc

gmaster
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby gmaster » Mon Feb 04, 2019 10:49 pm

My dealer did find a Command Thhrust Mercury 115 FOURSTROKE. He will have it in two weeks. I will have to decide whether to use my old analog gauges or upgrade to Smartcraft gauges. I also will most likely not be able to use my old RAPTURE 13.25 x 17 Prop. Both the new Montauk 170 and the new Dauntless 170 with the same Command Thrust 115 FOURSTROKE come with a factory installed Enertia 21-pitch propeller. That might be a good propeller to start with.

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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby Jefecinco » Tue Feb 05, 2019 10:23 am

I recommend the SmartCraft gauges. I have them on our 190 Montauk and find them to be very useful.
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby B.E.Coyote » Sat Jun 01, 2019 7:49 am

Any updates now that the weather is good?

Did you go ahead and get the Mercury 115?

I am not planning an immediate re-power, but I have been drooling over [the Mercury 115].

I am not thrilled with the performance of my 2000 Dauntless 16 with 2008 Yamaha F90.

The Mercury 115 would be 10-lbs lighter, have 25-HP, and 500cc additional displacement. I think the Mercury 115 would be the ticket.
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gmaster
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby gmaster » Sun Aug 18, 2019 11:11 pm

I have completed my repower with a 2019 Mercury 115 Command Thrust.

The new engine engine is much smoother and incredibly more quiet than my old Mercury 2+2 carburetor two-stroke.

I did install baystar hydraulic and a new smart gauge tach and new throttle control.

The propeller was supposed to be an ENERTIA 21, but an ENERTIA ECO 21 was put on.

I added an SE400 hydrofoil after a few trips. The anti-ventilation plate foil extension helped with [may mean helped with reducing] bow rise—just like on my old engine.

I am pleased so far. The low end torque is as good as my old engine. Top end is still around 41-MPH at 5100-RPM.

The old engine was incredibly rough at idle and hard to restart after it has been running for awhile. This has all been solved with the new engine.

I have forgot to turn it off twice putting it up on the boatlift because it is so quiet.


I definitely think the Mercury 115 Command Thrust model is a perfect engine for [a 160 DAUNTLESS] boat, based on its relatively low weight and good low end torque that helps with the bow lift and getting it on plane.

Lupi
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby Lupi » Mon Aug 26, 2019 6:38 am

Thanks for reporting your experience.

I would have expected top speed around 44-45 MPH @ something close to 6000 rpm (max rev).

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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby biggiefl » Mon Aug 26, 2019 9:45 am

5100 is too low. What is max RPM rating?
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

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Phil T
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby Phil T » Mon Aug 26, 2019 12:54 pm

Your dealer is not helping you very well.

The motor is rated with a WOT range of 5-6,000 rpm.

Note that propeller size and performance is not universal across models or brands. It is highly doubtful an Eco 21" with perform the same as a different model in the same size.

I agree with you Nick, and think the ECO prop is wrong. I would return it and go with the Enertia in 21" of pitch.

Confirm the engine is mounted 2 or 3 holes up.
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby biggiefl » Mon Aug 26, 2019 1:31 pm

Gonna have to drop some pitch if we need 8-900 more rpms.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby gmaster » Sat Sep 05, 2020 1:47 pm

I finally got around to changing the propeller to an ENERTIA 21-pitch from an ENERTIA ECO 21-pitch.

The ENERTIA 21 made a huge difference. The engine can now accelerate to a maximum speed of 5,600 to 5,700-RPM. The acceleration to hydroplane from a standing start with engine at full throttle is much better. There is less propeller CLUNK during low RPM engine speeds.

The ENERTIA ECO 21 was better in reverse propulsion that the ENERTIA, but that is not a huge deal.

I am happy with the current set up and the boat-engine-propeller is dialed in currently to my liking.

I will sell the ENERTIA ECO 21-pitch propeller.

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Phil T
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby Phil T » Sat Sep 05, 2020 4:02 pm

Bryan -

I recommend you raise the engine 1 additional hole and check the anti-cavitation plate (right above prop). Should be 1-1/2 inches above the keel of the boat.

Expect you will pick up ~2 mph and 150 rpm's due to less gearcase in the water.
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby Don SSDD » Mon Sep 07, 2020 6:01 am

Phil T wrote:BI recommend you raise the engine 1 additional hole and check the anti-cavitation plate (right above prop). Should be 1-1/2 inches above the keel of the boat. Expect you will pick up about 2-MPH mph and 150-RPM due to less gearcase in the water.
Would moving up the engine mounting height improve fuel consumption because of less drag at all speeds?
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Re: 160 Dauntless Re-power Mercury 115 FOURSTROKE

Postby Jefecinco » Mon Sep 07, 2020 9:46 am

Less drag should improve fuel economy at any speed but raising the engine higher than the optimal height can result in lower economy, shorter engine life, degraded steering control, more engine noise and probably other unintended consequences.

Regarding your specific question the degree of fuel economy improvement will be dependent upon speed through the water. At very low speed any improvement would be barely measurable while improvement at WOT would be much more apparent.
Butch