2001 Montauk 17 115-HP

Optimizing the performance of Boston Whaler boats
Peachdog
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2001 Montauk 17 115-HP

Postby Peachdog » Thu Oct 15, 2020 3:31 am

I have a [2001--always use FOUR DIGITS for years, please] Montauk 17 with a Mercury ProXS 115-HP engine and the LASER II 20-pitch propeller that came with the original engine [which apparently was not the Mercury ProXS 115-HP engine].

The [MONTAUK 17] runs great, but at full-throttle the Mercury ProXS 115-HP engine only accelerates to around 5,200-RPM. and the boat speed is 41-MPH. The Mercury ProXS 115-HP engine is rated for 6,400-RPM. The ProXS 115 will push larger and heavier boats 10-MPH faster with propellers of the same size as the LASER II 20-pitch, and those engines accelerate to 6,000 to 6,200-RPM--where the Mercury ProXS 115 is designed to run.

Q1: what is causing the MONTAUK 17 and the Mercury ProXS 115 to run slower?

Q2: is a different propeller needed in place of the LASER II 20-pitch?

On the newer model 170 MONTAUK with the Mercury 115-HP FOURSTROKE an ENERTIA 18-pitch propeller is standard, and the top boat speed is 46-MPH.

Q2: what is holding back [the boat speed for my MONTAUK 17 with Mercury ProXS 115]?

biggiefl
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Re: 2001 Montauk 17 115-HP

Postby biggiefl » Thu Oct 15, 2020 11:46 am

I assume a classic 17' and not a 170. Something is wrong. Have you broken in the new engine yet? Some do not perform correctly until a certain hour mark is reached to protect it. If so then follow Jim's suggestion and check linkage because you would need to drop to a 13" pitch to fetch 6400-RPM, and that is not right.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

MarkCz
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Re: 2001 Montauk 17 115-HP

Postby MarkCz » Thu Oct 15, 2020 12:19 pm

Is the engine mounted all the way down?

Or, do you have the engine mounting height elevated?

Peachdog
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Re: 2001 Montauk 17 115-HP

Postby Peachdog » Sun Apr 04, 2021 10:58 pm

The [Mercury ProXS 115-HP engine] is mounted [here the mounting height was described with an ordinal number--please describe engine mounting height in terms of the number of units of "holes" or 0.75-inches the engine is mounted above the lowest possible height, which in this case I believe you meant to be a mounting of one-hole-up from lowest position]---the same as the old 90-HP engine was mounted.

As of April 4, 2021, the [Mercury ProXS 115-HP engine] has 67 hours.

I tried a Turning Point 13.25 x 17-pitch propeller. The Turning Point 13.25 x 17-pitch propeller really improved acceleration [compared to a Laser II 20-pitch propeller], but the engine only accelerated [to a maximum engine speed of 5380-RPM] up 100-RPM from 5280-RPM with [the Laser II 20-pitch propeller] and [the boat speed declined] about 2-MPH. It [not sure which propeller is now "it" perhaps still means the Turning Point 13.25 x 17-pitch propeller] caused the boat to porpoise terribly. Even with 500-lbs in the [bow] of the boat or even with just me in [the boat], the [boat] still porpoised excessively at maximum boat speed.

I changed propellers on April 3, 2021, to use a Turning Point MAC-3 13.25 x 19-pitch. To my amazement for the first time [the engine] managed to [accelerate at full throttle to] 5,750-RPM and boat speed was either 45-MPH or about 46-MPH. [This boat speed is] the best I have managed to get out of [the Mercury ProXS 115-HP engine] so far.

The hull bottom could be cleaned, repainted, or buffed out. I think [those changes would cause boat speed to improve] 2-MPH based on [something] I have read.

Peachdog
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Re: 2001 Montauk 17 115-HP

Postby Peachdog » Mon Apr 05, 2021 12:10 am

[The boat under discussion here] is a Montauk 17--not the 170.

I checked the [engine] throttle linkage. As best I can tell [the engine throttle is] opening all the way. I will inspect it before I go out again.

I honestly don't know what kind of performance I should expect from this boat and engine combination. I just want [the boat performance] to be as good as it can be--particularly considering the amount of money I have spend on re-powering.

April 3 and April 4, 2021 have produced the best performance since [the Mercury 115-HP engine] was installed during the last week of August 2020.

[The engine speed of] 5740 to 5750-RPM, [the boat speed of] 45 to 46-MPH, and the fuel efficiency are really impressive.

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Phil T
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Re: 2001 Montauk 17 115-HP

Postby Phil T » Mon Apr 05, 2021 12:22 pm

Propeller performance is not all about size. You need to take into account the make and the model of the propeller.

From experience, a Montauk 17 with a 115-HP engine running light and mounted three-holes-up should be able to reach 49-MPH.

What model year is the Mercury 115 Pro XS?

The early versions had a gear ratio of 2.38:1 and the current motor has 2.07:1 gears. Need accurate information to use a propeller calculator.

If it is a current model with 2.07:1 gears
If we enter in key information: WOT rpm (6300)*, slip (5%), gear ratio (2.07)* and target speed (49), we get a recommended pitch of 18.
(* Per Mercury website)
If 2.38 gears it means a 20 pitch is recommended.

As for make and model of propeller, I would recommend a stainless steel prop. You don't specify model of Turning Point.

As for make and model I would start with a Mercury Enertia and PowerTech SCD.

I would not just throw props at it but discuss propeller selection with someone who knows Boston Whaler boats and propellers. Call either Dan's or Ken at Propgods.

http://www.dansdiscountprops.com
http://www.propgods.com

Note - Good props are very expensive: $400 to $800. Don't go cheap. That will be like buying a Ferrari and installing the tires from a Radio Flyer cart.
1992 Outrage 17
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Peachdog
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Re: 2001 Montauk 17 115-HP

Postby Peachdog » Fri Apr 09, 2021 3:48 pm

The 115-HP engine was made in May 2020. The gear ratio is 2.07:1

I have tested three propellers. I ran each propeller on multiple trips. The boat loading was fairly constant with two adults, one cooler with 20-lbs ice, fuel tank at 10 to 12-gallons, one Jack Russell terrier, and one anchor. Below are the test data. The engine speed and boat speed are for full throttle.

TEST 1
Propeller = Mercury LASER II 14 x 20-pitch
RPM = 5,280
MPH = 44

TEST 2
Propeller = Turning Point MACH 3 Express 13.25 x 17
RPM = 5,400 to 5,420
MPH = 43.5
There was repeated up-down oscillation of the bow (porpoising)

TEST 3
Propeller = Turning Point MACH 3 Express 13.25 x 19
RPM = 5,750 to 5,800
MPH = 46 to 47
There was no bow oscillation (porpoising)

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Phil T
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Re: 2001 Montauk 17 115-HP

Postby Phil T » Fri Apr 09, 2021 4:48 pm

It is clear you are not on the right path.

Also, the engine should be mounted two- or three-holes up, top bolt in the third or fourth hole down from the top. This is why you are porpoising.

I recommend you go back and read my prior post.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

Peachdog
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Re: 2001 Montauk 17 115-HP

Postby Peachdog » Fri Apr 09, 2021 5:13 pm

I am willing to try anything. I am by no means an expert. The 2001 MONTAUK 17 is really the first boat I have ever owned. I just want [the performance of the MONTAUK 17 with the new 115-HP engine] to be as good as can be.

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Phil T
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Re: 2001 Montauk 17 115-HP

Postby Phil T » Sat Apr 10, 2021 7:38 am

I would reach out to Ken or Dan.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

Peachdog
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Re: 2001 Montauk 17 115-HP

Postby Peachdog » Sat Apr 10, 2021 10:05 pm

I will call Prop Gods and see if they can steer me in the right direction.

jimh
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Re: 2001 Montauk 17 115-HP

Postby jimh » Sun Apr 11, 2021 9:31 am

Please renew this thread when you get another propeller and have more test data to present.