2003 170 MONTAUK Top Speed

Optimizing the performance of Boston Whaler boats
DiamondDog
Posts: 19
Joined: Sat Dec 16, 2017 5:12 pm

2003 170 MONTAUK Top Speed

Postby DiamondDog » Sat Dec 16, 2017 6:48 pm

Hi all. This is my first post. It is exciting to be part of the community after buying a 2003 Montauk 170 on Monday.

The first owner [of the 2003 170 MONTAUK] was having a lot of problems with his [Mercury outboard engine]. He re-powered with a 2009 Yamaha 90-HP two-stroke-power-cycle engine.

[Apparently on a seal trial of the 2003 170 MONTAUK boat with 90-HP engine] in calm conditions with two men [the] top speed was 35-MPH. Others report 42 to 47-MPH for this hull.

I did find a break in the [fiber]glass below [the] waterline and some damage at the bottom of the keel. The tap test revealed a few areas that needed repair, which are being included in the deal, along with storage and addition of a keel guard.

Buying as a personal sale from the owner of a very well-esteemed dealer. The [the 2003 170 MONTAUK] was kept in pristine condition, otherwise with regular maintenance his daughter used it.

The seller's dad and founder of the company is well-versed in Boston Whaler boats and didn't see much chance for any significant infiltration--but that would be revealed and repaired when the glass work is done.

I'm a little worried the lower high-end speed--which is fine with me unless towing a skier--is indicative of more water in the hull than expected. It was trailered when not in use. Could also be installation of the engine thatwas done by Yamaha dealer.

My first whaler. Am I being paranoid?

jimh
Posts: 11672
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 2003 170 MONTAUK Top Speed

Postby jimh » Sat Dec 16, 2017 11:33 pm

A top speed for a 170 MONTAUK with the Mercury 90 FOURSTROKE engine was about 43-MPH, based on a first-hand report from an owner of a 170 MONTAUK back in 2002. To only hit 35-MPH suggests that something is not quite right.

Assuming all factors are equal, to reach only 35-MPH compared to 43-MPH suggests that the effective horsepower has been reduced by a factor of (35/45)^2 = 0.66 or from 90 to 59-HP.

You cannot immediately assume the cause is added weight due to water absorption into the foam interior of the double-bottom hull. The Yamaha 90 might not be properly set up with a suitable propeller. To better judge the performance you need to give us more information. Tell us:

--the factory specified engine speed that should be reached at full throttle
--the engine speed reached at full throttle in RPM as read on the boat's tachometer gauge
--the gear ratio of the Yamaha engine
--the pitch of the propeller
--the engine mounting height

Ridge Runner
Posts: 199
Joined: Sat Oct 24, 2015 12:12 pm
Location: Florham Park NJ / Punta Gorda FL

Re: 2003 170 MONTAUK Top Speed

Postby Ridge Runner » Mon Dec 18, 2017 10:00 am

In 2003 the 170 Montauk would most likely have been powered by the Mercury 90HP two-cycle engine, a strong performing outboard (reported to be closer to 100HP). The 2009 Yamaha 90HP two-cycle engine is an excellent outboard that should last a very long time, but it is reported to be an under-performing engine with output in the 77HP range. The Yamaha has ~18% less displacement than the Mercury and in reported real life about ~23% less HP.

The Mercury 90HP Two-Cycle Spec's:
305 lbs. 3 cylinders, displacement is 84.6.

The Yamaha 90HP Two-Cycle Spec's:
261 lbs. 3 cylinders, displacement is 69.6.

I did a repower on a 16.5' Wahoo, much small and lighter than a BW 170 Montauk - (Wahoo - 725 lb dry weight, 16' 2" length x 6' 2" beam / 170 Montauk - 1,400 lb dry weight, 17'1" length x 6'10" beam) moving from a Mercury 90HP two-cycle to the Yamaha 90HP two cycle, I found the performance difference to be very noticeable. My top speed with the Yamaha was ~41MPH vs ~49MPH, and I really had to under-prop the motor to pull skiers.

I also have a 2005 170 Montauk which was originally powered with a Mercury 90HP two-cycle engine, my top speed was ~43MPH. Based on my experience I would expect your set-up to have a top speed of just a few more MPH than you are currently achieving by switching to a stainless steel semi-clever Yamaha propeller.

PICT0079.jpg
PICT0079.jpg (63.48 KiB) Viewed 9859 times
Member since 2005
2005 170 Montauk, 2010 E-TEC 115 H.O.
2016 210 Montauk, 2017 E-TEC G2 200 H.O.

"Red sky at night, sailor’s delight - Red sky in the morning, sailor’s warning”

User avatar
GoldenDaze
Posts: 165
Joined: Sun Apr 24, 2016 8:52 pm
Location: Virginia

Re: 2003 170 MONTAUK Top Speed

Postby GoldenDaze » Mon Dec 18, 2017 10:28 am

As Jim said, knowing what the propeller is will tell us a lot. My 2003 160 Dauntless with its Mercury 115 4-stroke will run at 43 mph with a 4-blade 17" Trophy Plus prop, but when I put on a 13" 3-blade aluminum Black Max I get a maximum speed right about 35 mph. It's great for pulling up skiers but obviously a terrible performer otherwise.

In other words, your boat speed might be exactly what would be expected, depending on what prop you are running.
2003 160 Dauntless Golden Daze

User avatar
Phil T
Posts: 2602
Joined: Thu Oct 22, 2015 6:08 pm
Location: Was Maine. Temporarily Kentucky

Re: 2003 170 MONTAUK Top Speed

Postby Phil T » Mon Dec 18, 2017 11:34 am

In addition to the above.

The factory mounted the engine 1 hole up (one empty hole above the bolt in the top brackets). 2-3 holes up is ideal. For each hole up you go the engine RPM's will increase by ~125.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

DiamondDog
Posts: 19
Joined: Sat Dec 16, 2017 5:12 pm

Re: 2003 170 MONTAUK Top Speed

Postby DiamondDog » Mon Dec 18, 2017 2:51 pm

Today I spoke with the boatyard and the Yamaha dealer. They said the engine's propeller [is] for [acceleration at full throttle from a standing start] [instead of] high end speed; they said this [propeller] is better in chop; they said the other propeller would only be good in calm water.

Which propeller is better for pulling skiers?

I thought [a propeller that produced] higher speed was better [for pulling skiers].

jimh
Posts: 11672
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 2003 170 MONTAUK Top Speed

Postby jimh » Mon Dec 18, 2017 3:05 pm

It is impossible to make any comments on anything you were told by the dealer.

Again, to better judge the performance you need to give us more information. Tell us:

--the factory specified engine speed that should be reached at full throttle
--the engine speed reached at full throttle in RPM as read on the boat's tachometer gauge
--the gear ratio of the Yamaha engine
--the pitch of the propeller
--the diameter of the propeller
--the material used to make the propeller
--the model designator or series name of the propeller
--the engine mounting height

I don't know how you expect to solicit any sort of advice when you describe one propeller as "this" propeller and another propeller as "another one." Those are completely meaningless descriptors. Come on--if you want some advice, offer some actual information. All we know is one value of boat speed and some remarks you heard from a dealer. We can't help you unless you provide some information.

User avatar
Phil T
Posts: 2602
Joined: Thu Oct 22, 2015 6:08 pm
Location: Was Maine. Temporarily Kentucky

Re: 2003 170 MONTAUK Top Speed

Postby Phil T » Mon Dec 18, 2017 3:54 pm

Performance of a boat with a certain engine/prop setup is almost as frequently asked as what year/model is my boat.

Given the extensive archive of this website, we have reports by members of motor, engine and prop testing. There are at least 3 props that are highly recommended for this engine/hull BUT we need one thing first.

We need DiamondDog to provide us the manufacturer, model and size of the current prop. The part # and size should be stamped on either the outside or inside of the hub of the prop. Once he provides this, we can move forward.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

DiamondDog
Posts: 19
Joined: Sat Dec 16, 2017 5:12 pm

Re: 2003 170 MONTAUK Top Speed

Postby DiamondDog » Mon Dec 18, 2017 8:50 pm

I have almost none of this information as I haven't taken possession of the boat yet, I'm not trying to be cagey or difficult --I laugh aloud--. The answers [have been] given already: the output of the Yamaha versus the Mercury and the prop sizing. Have essentially told me what I need to know. I was worried something more serious was wrong (mostly water in the hull).

My follow up question was about what kind of prop was better for waterskiing...one that gets you on a plane faster or one that has a higher top speed.

I have a picture of the engine mounted on the transom I'll try to post it here.

Thanks for your answers they were helpful.

whaler 6.jpg
whaler 6.jpg (48.57 KiB) Viewed 9801 times

flymo
Posts: 189
Joined: Thu Oct 22, 2015 2:58 pm

Re: 2003 170 MONTAUK Top Speed

Postby flymo » Tue Dec 19, 2017 10:37 am

In general, a prop that gets you on a plane faster is better for waterskiing.

Ridge Runner
Posts: 199
Joined: Sat Oct 24, 2015 12:12 pm
Location: Florham Park NJ / Punta Gorda FL

Re: 2003 170 MONTAUK Top Speed

Postby Ridge Runner » Wed Dec 20, 2017 12:21 am

You will want to get the propeller spinning up as quickly as possible in order to pull up a skier, so a small diameter propeller with limited cupping and some stern lift (bow lift is a problem when pulling up a skier - you want the bow of your boat to drop as quick as possible). I had good luck with my Yamaha 90HP two-cycle with using a small pitch Powertech SCD4 semi-clever propeller: http://www.ptpropeller.com/content-prod ... amaha.html

A semi-clever will allow the prop to spin-up and get the engine into its maximum torque band as quick as possible. I ran the Powertech SDC4 in a 13-inch diameter x 13-pitch for water skiing and used a standard 15-pitch three-blade propeller for regular cruising activities. You will need to under-pitch the propeller in order to have reasonable results pulling up a skier with that engine on a 170 Montauk. I do believe your underpowered for pulling skiers. Make sure you keep as much weight as you can out of the stern of the boat and have your spotter sit as far forward in the bow as you can.

I did a lot of skiing with my 170 Montauk and I re-powered with an Evinrude 115 E-TEC H.O. to be able to pull up larger skiers on one ski in deep water.

Also never pull tubes from the ski pole; that ski pole does not have the strength to pull tubes.
Last edited by Ridge Runner on Wed Dec 20, 2017 12:29 am, edited 1 time in total.
Member since 2005
2005 170 Montauk, 2010 E-TEC 115 H.O.
2016 210 Montauk, 2017 E-TEC G2 200 H.O.

"Red sky at night, sailor’s delight - Red sky in the morning, sailor’s warning”

DiamondDog
Posts: 19
Joined: Sat Dec 16, 2017 5:12 pm

Re: 2003 170 MONTAUK Top Speed

Postby DiamondDog » Wed Dec 20, 2017 12:27 am

This is all good info! Thanks

El Rollo
Posts: 87
Joined: Wed Sep 07, 2016 12:35 pm

Re: 2003 170 MONTAUK Top Speed

Postby El Rollo » Wed Dec 20, 2017 6:24 pm

Ridge Runner wrote: I had good luck with my Yamaha 90HP two-cycle with using a small pitch Powertech SCD4 semi-clever propeller: http://www.ptpropeller.com/content-prod ... amaha.html


That looks like a good propeller. Thank you for sharing that information.

I know you can't tell from a propeller's appearance how it will work on a particular hull, but when I switched to a 4-blade from a 3-blade I noticed increased stern lift and better [acceleration from a standing start at full throttle] immediately. My 1988 Boston Whaler 15 with Yamaha F70 and a 5-inch manual jack plate is definitely stern heavy; the 4-blade propeller helped the handling tremendously. It also pulls up waterskiers with no problem. This propeller that you have referenced actually mentions stern lifting in its description. I am very interested to try it. Thanks, again.