1987 Montauk 17 E-TEC 90

Optimizing the performance of Boston Whaler boats
jeffw920
Posts: 3
Joined: Thu Aug 24, 2017 9:50 am

1987 Montauk 17 E-TEC 90

Postby jeffw920 » Thu Aug 24, 2017 10:04 am

Hi everyone. I recently bought a 1987 Montauk with a 2014-year-of-production E-TEC 90. I've looked at the forum over the past few years but just recently registered and this is my first post.

The E-TEC 90 on my boat is a used motor with about 500 hours. It runs great but I think it may be propped incorrectly. Currently the E-TEC 90 has a 17 VIPER propeller. It accelerates like crazy but seems to lack a little on the top end and generally runs at an engine speed that is too high for the boat speed.

For example, I get 25-MPH boat speed at 4,000-RPM engine speed; and 35-MPH at 5,700-RPM at full throttle. I believe 5,700-RPM is a bit outside the recommended range for this engine.

I don't generally run that fast. (Actually the one time I ran WOT with only me on the boat I blew the main engine fuse--not sure if that is related.) I prefer to run about 3,500-RPM but currently that is only about 20-MPH boat speed.

The E-TEC 90 is mounted on an aluminum setback plate with the A-V plate about 2.5 to 3-inches above the bottom of the hull. The setback plate was not my doing and I'm debating removing it this winter. I don't know how much role this may be playing in the performance characteristics.

I'm quite familiar with the following page:

http://continuouswave.com/ubb/Forum4/HTML/004278.html

which offers an excellent comparison of propellers. For whatever reason my performance does not seem to match up.

Do you guys recommend going up in pitch to say a 19 VIPER?

Or, considering another 17-pitch propeller, that may perform better when pushing a Montauk?

Thanks for any advice.

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

Re: Prop for etec 90 on 1987 montauk

Postby Phil T » Thu Aug 24, 2017 1:29 pm

While your speed is really off (compared to that thread) I think there may be something else going on.

Please describe:

- How many inches of setback is there?
- Does the boat sit with the rear drain tubes above the water

Speed measured on slightly calm, no wind, back and forth runs via GPS?

- gear,fuel,batteries in the boat
- Bottom paint? Condition?
- T-top?

The recommended WOT rpm range for the E-TEC 90 is 5500 so you are definitely underpropped.

Before going to a 19" Viper, there may be an engine mounting concern too. For every 6" of setback, you want to go up an additional 1".
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

jeffw920
Posts: 3
Joined: Thu Aug 24, 2017 9:50 am

Re: Prop for etec 90 on 1987 montauk

Postby jeffw920 » Thu Aug 24, 2017 5:33 pm

A back-and-forth run (on river, like glass) yields an average of 38-MPH SOG per GPS.

The Set Back Bracket is from Vance manufacturing and is a 6-inch setback unit.

Without no one aboard the MONTAUK 17, seawater just barely creeps in the scuppers The boats sits nice and level, and I don't believe there is any excess water in the hull.

Gear aboard is negligible: a couple lifejackets, anchor, me (190lbs), one battery in the console, and a nearly full 22gallon fuel tank.

There is no T-Top.

The condition of the bottom is crappy: many layers of old crusty bottom paint that is worn through and chipping all-over from a good pressure washing.

The outboard engine sounds effortless throughout its RPM range.

The propeller grips tightly in corners.

I wonder if lowering the outboard a bit might help. What's [is your opinion] on setback plates for a Montauk?

Thanks

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

Re: Prop for etec 90 on 1987 montauk

Postby Phil T » Fri Aug 25, 2017 8:19 am

The expectation of the classic Montauk running light, with an E-TEC 90 mounted 3 holes up with a good stainless steel prop is 42-45 mph.

You may want to raise your engine 1 hole and retest. E-TEC's like to be mounted much higher that other motors. Most owners have them at the highest height possible. This will exacerbate your current underprop situation.

I think you will want to go with a 19" Vengence. If you change brands, the size is going to be different. Blade design makes sizing not universal.

Here is a list of tested props by Whaler members that are solid:

13.25x17 Stiletto ADVANTAGE 1 (Discontinued)
13.25x19 Stiletto ADVANTAGE 1 (Discontinued)
13.5 x 20” Raker
13-7/8" x 17" BRP Viper
13-1/4" x 17" SST (note: 2 holes up)
13-1/4" x 15" Turbo 1

I would revist the engine height after re-propping. Read the top 1/2 of this thread where they discuss setback brackets.
http://continuouswave.com/ubb/Forum4/HTML/007601.html

I am not a speed freek. All the tweaking is so that the engine performs at WOT which will translate to most efficient at all speeds.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

jeffw920
Posts: 3
Joined: Thu Aug 24, 2017 9:50 am

Re: 1987 Montauk 17 E-TEC 90

Postby jeffw920 » Mon Aug 28, 2017 9:33 pm

Phil,

Thanks for the reply. I'll give the props you listed a look. I'm not interested in squeezing every last mph out either. Just want it to cruise efficiently at a comfortable rpm.

jimh
Posts: 11670
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 1987 Montauk 17 E-TEC 90

Postby jimh » Fri Sep 01, 2017 9:58 am

Over the years I have come to doubt that use of a set-back bracket really adds a great deal to the performance of most smaller Boston Whaler boats. I think set-back brackets are a something of a fad that crept into Boston Whaler boats from Bass Boats, where they are deemed to be standard equipment. Bass boats like to go 70-MPH in very shallow lakes with dead flat calm water. Boston Whaler boats, particularly the smaller ones, are 35-MPH boats at best, and spend most of their time on plane around 25-MPH.

A set back bracket is useful to make adjustments to engine mounting height. You can experiment with engine mounting height more easily with a set back bracket than you can with re-installing the engine on the transom mounting holes.

With modern engine weight creeping upward, adding a setback bracket seems like just more weight on the transom, and further moves the big weight--the engine--back from the hull's overall center of balance. This generally results in a more bow-up static trim.

I believe what often happens is a Boston Whaler boat owner spends $400 for a set-back bracket, takes a lot of time and labor to install it, and then really never completely evaluates what effect it has had. After all the time and expense of installing one, there is a bias toward finding it has improved performance. No one likes to say, "I spent $400 and two weekends putting on this set back bracket and saw no difference."

jimh
Posts: 11670
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 1987 Montauk 17 E-TEC 90

Postby jimh » Fri Sep 01, 2017 10:18 am

For advice on the optimum speed range for E-TEC engines, see the REFERENCE article at

E-TEC Recommended Engine Speed Range
http://continuouswave.com/whaler/reference/ETEC_EngineRPM.html

For your engine the recommended optimum speed range is 5,000 to 5,200-RPM.

For assessment of the current set up, with a propeller of pitch 17, and engine speed of 5,700-RPM, and a boat speed of 35-MPH, we need one more element: gear ratio. It is much appreciated if the OP can give the gear ratio of the engine in any posting asking for advice. I looked up the E-TEC 90; I think it has a gear ratio of 2:1, based on current production engines. Now we can assess the current propeller on this basis:

RPM = 5700
RATIO = 2
PITCH = 17
MPH = 35

We calculate SLIP to be 24. (See viewtopic.php?f=7&t=41 for calculator links)

That is much too high. SLIP should be about 10 or less, and at best trim and highest speed should be below 10.

A reasonable inference about why SLIP is so high: the propeller is running in airy water and does not like it. Try lowering the engine mounting height to get the propeller into more solid water.

Using the propeller calculator, we make a trial calculation for boat speed with the parameters given below:

RPM = 5200 (the recommended optimum)
RATIO =2 (fixed by the engine)
PITCH = 19 (a trial pitch to see what we get)
SLIP = 10 (a reasonable value for good set up_

A calculated MPH would be 42-MPH. This is the target mentioned by Phil.

I think that is about the best you could ever do with an E-TEC 90 on a MONTAUK.

Sticking with a 17-pitch, if you could get the SLIP down to 10 the boat speed would be 38-MPH at 5200 and 40-MPH at 5,500-RPM. Those are good speeds for a MONTAUK and a 90-HP.

Here is some good data on E-TEC 90 and MONTAUK 17 performance from a trusted source:

http://continuouswave.com/ubb/Forum4/HTML/002465.html

Please note that the testing was done at sea level in colder saltwater; if you are testing in warm freshwater you will not get the same results. Warm freshwater has lower density than cold saltwater, and this automatically reduces the performance of a propeller and engine. Other influences are air temperature, humidity, and elevation. Engine performance decreases with elevation above sea level. If you test on an inland lake at 900-feet elevation, performance will be less than at sea level. Engine performance decreases with increasing air temperature and humidity. An engine tested at sea level in cold saltwater on a cold low-humidity day will perform better than the same engine tested in warm freshwater at 900-feet elevation on a hot and humid day.

Also note that the power output of modern outboard engines is a function of the particular engine firmware loaded into them. Over the 13-years since Rob reported on his 2004 E-TEC engine performance, the firmware in the engine has evolved. It is entirely possible that the actual power output available from a c.2017 engine could be down a few horsepower from a c.2004 engine due to changes in the firmware that were made by the manufacturer. Reasons for this could be almost anything, from a desire to lower exhaust emission gases of a certain type, to a concern to limit power output for any number of reasons, such as marketing or longevity or other performance factors like smoothness. The important aspect is that you cannot bet the farm that a new c.2004 engine and a used c.2014 engine will have exactly the same power output under substantially different environmental conditions. A final factor is fuel: if you use gasoline-ethanol blended fuel it will reduce engine power output compared to running on pure gasoline.

Finally, propeller pitch as stated by the propeller maker is not a universal absolute. The 17-pitch propeller tested by Rob may have had an effective pitch that is higher than some other maker's 17-pitch propeller.

ASIDE: as it happens, I have been aboard Rob's MONTAUK and driven it briefly. It was a wonderful boat and performed beautifully.

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

Re: 1987 Montauk 17 E-TEC 90

Postby El Rollo » Fri Sep 01, 2017 8:52 pm

jimh wrote:I believe what often happens is a Boston Whaler boat owner spends $400 for a set-back bracket, takes a lot of time and labor to install it, and then really never completely evaluates what effect it has had. After all the time and expense of installing one, there is a bias toward finding it has improved performance. No one likes to say, "I spent $400 and two weekends putting on this set back bracket and saw no difference."


This is classic jimh rhetoric. God forbid anyone do anything outside the Desert Tan boundaries of the Dougherty-Fisher era.

News Flash: Cruising around "toot-toot" style with a Whaler burgee and your dock lines flemished correctly afterwards in a 1980-era chopper-gun production boat doesn't always appeal to the masses. I've spent plenty of hours on this site researching legitimate topics, only to have to sift through countless miles of jimh rhetoric on how to tie a correct clove hitch when a proper cleat is not available.

I spent five years restoring a 15 Whaler with plenty of resources at my disposal. I've owned five classic Whalers and am looking to purchase my sixth.

I can tell you the upsides and downsides of putting a jackplate on a 15'Whaler, or any other Whaler for that matter--it's no mystery. I just don't need Thurston Howell the fourth telling me I'm wrong for doing it.

Everyone appreciates the time time and effort jimh put into this website. It's arguably the single greatest resource for Boston Whaler information, and I doubt anyone would contest that, and for that we are all eternally grateful. But you've gotta let it go once in a while dude.

I know this post will be deleted. Just like everyone else who gets their posts edited for grammatical errors , sentence structure, and punctuation.

Time to get current, and Let it Go Bro

Cheers

El Rollo

Whal
Posts: 35
Joined: Thu Jan 14, 2016 7:11 am

Re: 1987 Montauk 17 E-TEC 90

Postby Whal » Sat Sep 02, 2017 7:13 am

Years ago when the E-TEC 90 first came out there were a lot of posts on this subject and the hot prop was the Stilletto Advantage 13.25 x 15 mounted (I'm pretty sure) two-holes-up on the transom with no jack plate. The Stilletto Advantage props were said to run one-size bigger than they were marked. A 15 ran like a 17 and a 17 ran like a 19, etc. I sold a Stilletto Advantage 13.25 x 15 that I had to a guy with an E-TEC 90 on a Montauk 17, and I think he got 42 to 43-MPH at max RPM. You should be able to look back at old posts from a few years ago and get a wealth of information on this topic as this is a very popular motor on the Montauk 17.

jimh
Posts: 11670
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 1987 Montauk 17 E-TEC 90

Postby jimh » Sat Sep 02, 2017 9:24 am

ROLLO--If you have some data to share about the topic you ought to present your data. Show us the data. Your little rant about me and the website is not the sort of information the website tries to collect nor what people come to the site to read--as you said, it is not "a legitimate topic." My expression of doubt about the real usefulness of set back brackets on 17-foot boats, that is a legitimate topic.