2005 MONTAUK Mercury 90-HP FOURSTROKE

Optimizing the performance of Boston Whaler boats
WYEMILLSWHALER
Posts: 2
Joined: Sun Jun 21, 2020 4:16 pm

2005 MONTAUK Mercury 90-HP FOURSTROKE

Postby WYEMILLSWHALER » Sun Jun 21, 2020 4:19 pm

[MOVED to PERFORMANCE for discussion and author notified--jimh]

[Give me] advice [on propeller selection for a 2005 MONTAUK of unspecified length--please always mention the model length].

A BLACK MAX three-blade aluminum 13-1/4 x 17-pitch [allows the 2020-production year Mercury 90 FOUSTROKE engine to accelerate] to only 5,100 RPM with [proper engine] trim.

I [believe engine speed at full-throttle] should be around 5,500-RPM.

Any help would be great. Thanks

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

Re: 2005 MONTAUK Mercury 90-HP FOURSTROKE

Postby jimh » Mon Jun 22, 2020 10:35 am

The owner's manual that was provided with your 2020 production epoch Mercury 90 FOURSTROKE will list the recommended engine speed range for full-throttle operation. Please pass along that important information by a reply post what the manual says.

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

Re: 2005 MONTAUK Mercury 90-HP FOURSTROKE

Postby jimh » Mon Jun 22, 2020 10:39 am

In order to offer advice on propeller selection, readers will need to know more information that you must provide:

--what is the length of the 2005 MONTAUK boat you are asking for advice?

--what is the boat speed in statute miles0per-hour at maximum throttle?

--what is the gear ratio of the engine?

--how was boat speed measured?

--what were the environmental conditions during the on-the-water testing, such as air and water temperature, winds, current, sea state

--what was the load of passengers, fuel, gear, aboard when testing?

Rascal
Posts: 23
Joined: Thu Oct 29, 2015 10:07 pm

Re: 2005 MONTAUK 2020 90 HP MERC 4STRK

Postby Rascal » Mon Jun 22, 2020 10:51 am

In addition to the information Jim mentioned, it would help to know what your goals are: Will you typically have 1 person or 7 people onboard? Maximize top speed, hole shot, or fuel economy? Do you have bottom paint?

As a comparison, my 2015 170 Montauk with 90-HP FOURSTROKE EFI came from the factory with a Vengeance three-blade prop 13-1/8 x 16-pitch (PN 48-16986). It reaches the maximum RPM range ( about 5750-RPM). It's a well rounded prope;;er that works well for two to seven people on board and for water sports or cruising. Reducing your pitch to 16 from 17 will increase engine speed by about 200-RPM. Moving to a stainless propeller from an aluminum propeller will also increase engine RPM some. One or both of these changes will put you more in the middle of a 5000 to 6000 maximum RPM range--the same maximum range as my engine.
Rascal (Scott)
2015 170 Montauk

WYEMILLSWHALER
Posts: 2
Joined: Sun Jun 21, 2020 4:16 pm

Re: 2005 MONTAUK Mercury 90-HP FOURSTROKE

Postby WYEMILLSWHALER » Mon Jun 22, 2020 11:05 am

2005 17 MONTAUK

2020 90-HP Mercury FOURSTROKE

No more than three people on board.

I tired a 17-pitch still didn't hit the 5500 RPM

Thanks for the help

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

Re: 2005 MONTAUK Mercury 90-HP FOURSTROKE

Postby Phil T » Mon Jun 22, 2020 12:55 pm

The Mercury 90 hp engine offered on the Montauk 170 has changed three times since the boat model was first introduction in 2002.

From 2003-2018 the Mercury 90 FourStroke had a 2.33 lower unit.

For the 2019 and later years, the Mercury 90hp FourStroke has a gear ratio of 2.07. The Command Thrust option has 2.38 gears.

I would recommend the 13.15 x 18 Mercury Vengance for the 2020-production epoch Mercury 90 FourStroke on a classic Montauk 17 mounted at least two holes up. This size recommendation only applies to the specified make and model of propeller listed.

Aside: In checking specifications, note the current Montauk 170 II has a dry weight that is twice as much as the classic Montauk 17. 950-lbs v. 2050-lbs.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

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

Re: 2005 MONTAUK Mercury 90-HP FOURSTROKE

Postby jimh » Mon Jun 22, 2020 5:37 pm

Thanks for responding that the boat under discussion is a 2005 17-foot Montauk. I presume it is a 170 MONTAUK model. If that is not true, please reply to correct.

Still unanswered are my other questions, which I repeat:

In order to offer advice on propeller selection, readers will need to know more information that you must provide:

--what is the boat speed in statute miles-per-hour at maximum throttle?

--what is the gear ratio of the engine?

--how was boat speed measured?

--what were the environmental conditions during the on-the-water testing, such as air and water temperature, winds, current, sea state

--what was the load of passengers, fuel, gear, aboard when testing?

biggiefl
Posts: 897
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
Contact:

Re: 2005 MONTAUK Mercury 90-HP FOURSTROKE

Postby biggiefl » Tue Jun 23, 2020 12:23 pm

Since this was a fresh repower, are you getting WOT at the engine?

An error on throttle or shift linkage could be the problem. But I would leave the remedy to whomever installed the engine.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).