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Author Topic:   Montauk: E-TEC 90 Propeller comparison.
ratherwhalering posted 03-17-2006 11:39 PM ET (US)   Profile for ratherwhalering   Send Email to ratherwhalering  
The folllowing is a comparison of two different propellers tested on the same day, on the same Whaler, in similar conditions.

The boat is a 1987 17-Montauk, full gear including 8lb anchor, anchor line, bow seat, cooler, 4 lifejackets, small tool kit, first aid kit, console cover, RPS cover, VHF with low profile antenna, Pate C-27 gas tank with 26 gallons of gas, stern mounted Raycor fuel filter, stern mounted West Marine Group 27 battery.

The engine is a 2004 Evinrude E-Tec E90DSLSR. (In-line 3-cyl E-TEC). Bore 3.600 x Stroke 2.58879, with a 1295 cu displacement. 90 HP (67 kw) @ 5000 RPM, with a full throttle range of 4500 to 5500 RPM. Fuel induction is E-TEC Direct Fuel Injection w/stratified low RPM combustion mode. The lower unit has a gear ratio of 2:1.

The engine is mounted via a Cooks Manufacturing two-piece adjustable manual set back plate, with the full height of the 5" of slot adjustment at the motor mounting bracket, and the lowest 1.5" of adjustment at the transom bracket. 4-inch setback. The anti-cavitation plate is approximately 2 7/8" from the lowest transom point. 215lbs operator.

PERFORMANCE (via GPS on flat water, slight wind ripples)

Propeller: OMC SST II 13 7/8" x 17" painted stainless steel.
Date: 03/17/06
Air Temperature: 60 degrees
Wind/Water: 8-10 knts./calm with ripples
Fuel: 26 gallons

750 3.3
1000 4.5
1500 6.6
2000 8.0
2500 16.0
3000 21.5
3500 26.0
4000 31.2
4500 35.0
5000 38.6
5500 42.5

Propeller: Stiletto 13.25" x 15"� three bladed polished stainless steel.
Date: 03/17/06
Air Temperature: 65 degrees
Wind/Water: 8-10 knts./calm with ripples
Fuel: 26 gallons

750 3.4
1000 4.3
1500 6.7
2000 8.1
2500 16.7
3000 22.5
3500 28.0
4000 32.7
4500 35.7
5000 39.5
5500 42.8

Performance notes: The OMC propeller had moderate cavitation, while the Stiletto had nearly none. The Stiletto felt more responsive at low, mid and upper ranges, however it was very sensitive at 5000 RPM and above, where the OMC was much smoother at WOT.

A very large thanks to Tom Clark for lending me the OMC propeller, the test spreadsheet format, and the motivation to go out and do this comparison.

fishgutz posted 03-18-2006 12:05 AM ET (US)     Profile for fishgutz  Send Email to fishgutz     
I love to see comparisons like this. Nice job. Nice to see some real numbers with an E-Tec to boot.
Perry posted 03-18-2006 12:27 AM ET (US)     Profile for Perry  Send Email to Perry     
Now that's what I call good data. It's very useful when the vital info is included.

42+ mph isn't bad. How was the holeshot comparison? Did you trim it all the way out to achieve the 5500 RPM?

jimh posted 03-18-2006 12:29 AM ET (US)     Profile for jimh  Send Email to jimh     
Here is a very accurate graphing of those results:


(This is not your usual sloppy spreadsheet graphing output--
this is an accurate plot of the data.)

Peter posted 03-18-2006 12:57 AM ET (US)     Profile for Peter  Send Email to Peter     
Looks like that E-TEC 90 on the classic Montauk could turn a 19 inch OMC SST propeller with a light load.

We can get a rough idea of fuel economy for the SST propeller at various speeds by combining Rob's speed numbers with absolute fuel consumption(GPH) at RPM taken from other E-TEC 90 data taken from here Aquasport+175+Osprey.htm . Here's what the rough idea for fuel economy looks like:

5500__8.20__42.5_____5.2 Guestimated the GPH on this one.

The same can be done for the Stilletto propeller using the same GPH data. The Stilletto will probably provide better fuel economy across the range.

Tom W Clark posted 03-18-2006 02:22 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

Nice job. Its like a breath of fresh air to see good data for a change. None of this "I used to X MPH with my ol' whatever-it-was boat..."

So in the end, the 17" SST performed very much like the Stiletto 15" confirming that these Stilettos do seem to have more pitch than their nominal measurements.

Furthermore, I conclude that all around, the Stiletto was the better propeller. Do you concur?

All of this has me wondering: What other propeller could we (you) try that perform any better. What's the hottest prop out there for this size of motor? Or are the Stilettos simply the BEST?


Nice estimates. I think its remarkable that this boat/motor combo can do 7 MPG at a swift 26 MPH! I sure wish I could get that with my 25 ;-)

jimh posted 03-18-2006 02:30 PM ET (US)     Profile for jimh  Send Email to jimh     
The graph shows the better mid-range performance of the Stiletto. At 3,500-RPM, which is a favorite cruising speed for the engine, the Stiletto propeller is 2-MPH faster than the SST-II. This seems to be where the newer designs in propellers really show their improvement: at moderate speeds the newer style propellers are more efficient, producing more boat speed and less SLIP.
Peter posted 03-18-2006 02:42 PM ET (US)     Profile for Peter  Send Email to Peter     
The engine running height may not be optimized for the SST if it was optimized for the Stilleto. So I think it's possible that the SST could perform better but we really wouldn't know unless Rob played around with the engine running height to see if that made any favorable difference.

That 7 MPG at 26 MPH is about 5 times better than what I get on my 27 Whaler WD. My Navman 3100 says I get 11 MPG at idle speeds! ;)

erik selis posted 03-18-2006 02:50 PM ET (US)     Profile for erik selis  Send Email to erik selis     
This is very good information. Thank's Rob! (and all the others who helped out here)


Perry posted 03-18-2006 04:57 PM ET (US)     Profile for Perry  Send Email to Perry     
While 7 MPG souds good at cruise speed, (I get 6+ MPG on my 190 Outrage/Nantucket at cruise) what really impresses me about this E-TEC is the 5+ MPG at WOT. That is very good fuel economy.
Tom W Clark posted 03-18-2006 05:11 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

That is a very good observation. It fits with my impressions of the 90 HP E-Tec.

Recently, there has been much FUD strewn about here in regards to the 90 HP E-Tec. Really the only thing anybody can say about this motor is that its top speed seems to be slow. From this is drawn the implication that this motor is not as strong as other 90 HP motors.

My experience running the 90 HP E-Tec is that it is not as fast at the top end as my old 90 HP V-4 Johnsons. But this obscures the fact that this motor behaves like a MUCH stronger motor up until the very end of its throttle range.

Out of the hole or even slamming the throttle forward at cruise speeds, the E-Tec will snap your neck. It is almost as if the motor is designed to not make full use of its top end power. This may be evidenced by its miserly fuel consumption at WOT.

It's almost as if there is more throttle you just can't access.

I would love to see some REAL testing/comparisons between the 90 HP E-Tec and other 90 HP motors that don't just look at top speed (a speed range mostly irrelevant to us.)


I imagine the SST would be happier with the motor mounted lower, not higher. Do you think lowering the motor would improve the top speed of the SST?

fourdfish posted 03-18-2006 07:08 PM ET (US)     Profile for fourdfish  Send Email to fourdfish     
Tom-Just thinking here, but this engines power curve is tuned by the software. I think the software engineers could change the top end at the expense of the other factors you mentioned.
Isn't it just a trade off!
Peter posted 03-18-2006 08:07 PM ET (US)     Profile for Peter  Send Email to Peter     
Tom -- Just don't know whether top end would be improved. It's certainly contrary to the conventional wisdom to lower the motor. I do think that it is possible that the mid-range efficiency could be improved by lowering the motors. My short experience with a pair of 15 x 17 SSTs on my 27 was that they broke loose quite easly and suspect that they were not running low enough in the water with the way my motors are set up on the transom.
ratherwhalering posted 03-19-2006 10:39 AM ET (US)     Profile for ratherwhalering  Send Email to ratherwhalering     
Hi guys, sorry about the late post, but I left for the weekend right after posting the results. Perry, the holeshot on the SST was fine, but not nearly as good as the Stiletto, and I had to trim way out with both to hit 5500. Tom, no doubt I prefer the Stiletto, but to be fair, Peter is right. I'll need lower the engine, then test the SST, because it was blowing out quite a bit on hard accelleration, and heavily cavitating in tight turns at low speed, especially when finishing a tight turn. The rig is optimized for the Stiletto, and I'm planning on dropping the brackets at least 1.5 inches and retesting the SST. I'm out on the water (sailboat racing) today, but I'll see if I can get this done this late afternoon.

Overall, the Stiletto feels like it grips better, planes easier, and has better mid-range performance. This may change when I give the SST a little more bite. On the current set up, frankly the SST feels soft, but remember my engine is really high.

The top end on the E-TEC 90 is very different from my old Johnson V-4. The E-TEC's hole shot is better, and the E-TEC bangs right up to 4800 RPM, but then creeps to 5500. It feels like it is programed to take its time to get to WOT, while the Johnson hit WOT on a steady power curve. I think if you were to do a side by side comparison, you would see the E-TEC pull ahead in low and mid range, but the V-4 would catch up at top end, and then the two would even out.

Tom W Clark posted 03-21-2006 09:49 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
I am surprised nobody has made any recommendations of props to try. Is the Stiletto the BEST PROP MADE?

Does Mercury have nothing worthy that might be tested against it?

Does not Bombardier produce any props for the midsize motors other than their highly successful 25 year old SST design?

ratherwhalering posted 03-21-2006 11:37 AM ET (US)     Profile for ratherwhalering  Send Email to ratherwhalering     
If anyone has a prop they would like to donate for a week or so, I slap her on and do another performance test!
Budysr posted 03-21-2006 12:56 PM ET (US)     Profile for Budysr  Send Email to Budysr     
I am using a viper on my 90. Mine is a 19", and I belive its the same diameter as that SST. I'd like to see how a viper does on Rob's setup. I may be wrong but as I understand it the viper is more of a high performance prop than the SST(could be wrong though). Too bad I don't live in California. I'd love to trade props with Rob for a day to do a comparison.
LHG posted 03-21-2006 03:07 PM ET (US)     Profile for LHG    
To answer Tom's question, Mercury has nothing worthy to test in the performance series on this boat/engine combination. In the 4-1/4" mid range gearcase, Mercury uses lower gear ratios (numerically higher), which is why I say this engine doesn't have enough power to push a 2.0 ratio. It should have 2.33 gears.

The only Merc prop he could try would be the 16" Vengeance, and the engine would have to be dropped way down. But since this is an elepant ear ordinary prop, it will not be any faster (although it probably will be AS fast, like the OMC SST was).

Mercury basically doesn't make performance props for these mid range engines below 20" pitch, as they say the speed doesn't require it and the Vengeance and aluminum props do the trick. They make a 17" and 19" 4-bladed Trophy, but these are mostly for the higher geared V-6 large gearcases, where you intentionally get the gas blowby from the larger diameter hub, on fast bass and flats boats. The 2.33 ratio 90's use them also. There is no way Rob's engine could turn a 20" Laser II or 20" High Five prop. With 2.0 gears, you need to be running in the low 50's to use them.

On a Boston Whaler Classic Montauk, if you want to go 43 MPH or better, it appears you need a more powerful engine than the 90 Evinrude E-tec. I recommend Rob enjoy the low end performance of the engine and leave it at that (and don't race any old fashioned 2-stroke Merc 90s, 3 OR 6 cylinders!

Peter posted 03-21-2006 03:59 PM ET (US)     Profile for Peter  Send Email to Peter     
Rob/Tom -- If you could ever find an a rare 13 1/2 x 18 inch Raker, that would be a good one to try.

Tom W Clark posted 03-21-2006 07:13 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

I don't think the 13-1/2 x 18 Raker is the prop for a Montauk. BRP states that these props are for boats that go 46-56 MPH. I have also heard that the Raker (like the Stiletto Advantage) is a prop that has effectively more pitch than its nominal specification, i.e., it will perform like a 20" pitch prop.

Rob and I were talking on the phone today and we think the Viper would be the next BRP prop to try out. It seems to be a high quality version of one of the two 17" SST props made by BRP.

Yes, that's right, there are TWO 17" SST props offered by BRP:

#177035, 13-3/8" x 17"

#176572, 13-7/8" x 17"

The prop Rob has now is part #389948, 13-3/8" x 17" which would seem to suggest it is an older version of #177035, but we have not been able to confirm this.

Years ago I recall OMC selling both SST and SST II props where the former was cupped and the latter was double cupped. Does anybody have any REAL knowledge about these part numbers?

Peter posted 03-21-2006 08:27 PM ET (US)     Profile for Peter  Send Email to Peter     
I think the 18 Raker is likely turn like a 19 SST which is why I suggested it. The 17 inch SST is turning right up to 5500 so there is room to go up in pitch for a light load.
Teak Oil posted 03-21-2006 09:40 PM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
I have to disagree with Tom on this one, I think a Raker would make a great prop to try because I am running one right now and love it.

I have a 13.5 x 20 Raker on my V4 and it turns 5300 loaded, about 5500 with a light load and trimmed way out.

I have it raised fairly high with the jackplate, and the prop has great holeshot and does not blowout in turns. It also handles rough water great, just as Buckda. I think the 18" model like Peter suggested would bring Rob's rpms down a hair to see what the E-Tec can pull.

Tom W Clark posted 03-21-2006 11:10 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
OK, I'l listen to you guys. The 18" Raker remains on the short list...


Actually it is the VIPER that is the same blade geometry as the SST, not the Raker.

I answered my own question above. There are two different SST props, one with "non-swept" blades (the 13-3/8" diameter) and one with "swept blades" (the 13-7/8" diameter). The VIPER appears to be nearly identical to the 13-7/8" x 17" SST but with a polished finish.

Peter posted 03-22-2006 12:50 AM ET (US)     Profile for Peter  Send Email to Peter     
Yes, there is a more recent version of the SST that looks just like the Viper. They share the same dimensions and the same blade shape. It looks like Rob was running that one instead of the old OMC SST II that dates back to the late 1970s or early 1980s. If that is the case, I don't think the performance would be much different than the Viper. I would give a 19 inch Viper or recent SST a try just for fun.
Buckda posted 06-05-2009 11:43 AM ET (US)     Profile for Buckda  Send Email to Buckda     
I would like to append this discussion with some additional results in testing a 13.25x15 Stiletto ADVANTAGE 1 vs. 13.25x19 Stiletto ADVANTAGE 1 on a Montauk with 90-HP E-TEC.

This information is reported by Terry Hoy on his 1989 Montauk with 2005 E-TEC 90 HP motor. 10 gallons of fuel, one person aboard, speed via GPS.

15-pitch prop:
19.3 MPH at 3,000 RPM
42.4 MPH at WOT - 5,700 RPM

19-pitch prop:
22.7 MPH at 3,000 RPM
44.5 MPH at WOT - 5,200 RPM

This is right in line with the performance of the classic cross-flow and loop charged OMC 90's on these hulls.

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