1990 REVENGE 22 W-T Whaler Drive, E-TEC 225

[jimh]

It has been several years since I gathered any performance data on my 1990 Boston Whaler REVENGE 22 Walk-Through Whaler Drive boat with a 2010 Evinrude E-TEC 225. Below is data from a recent test. The engine is now in its 11th season of use. The engine mounting height throughout the testing is one-hole-up on the Whaler Drive.

Performance Data

BOAT, ENGINE, PROPELLER

Boat: REVENGE 22 Walk-Through Whaler Drive, 1990

Engine: E-TEC 225, Evinrude, 2010-model-year, E225DPXISE
Recommended WOT RPM Range: 4500 to 5800-RPM
Optimum WOT RPM Range: 5500 to 5700-RPM
Gear ratio: 1.86:1
Mounting height: one-hole-up

Propeller: Mercury MIRAGEplus 17-pitch three-blade stainless steel PN 48-18278
Diameter 15-1/2-inches
Length 6-3/4-inches
Exhaust port flare diameter 4-7/8-inches
PVS vents: closed
Hub Kit: FLO-TORQ II

TEST CONDITIONS

Date: July 12, 2019
Air Temperature: 77-degrees
Wind: 5-knots
Current: none
Humidity: unknown, probably 50- to 70-percent, a nice Summer day
Waves: small with some boat wakes mixed in
Crew: two aboard; total crew weight 360-lbs
Canvas: Flying Top deployed
General gear: normal non-overnight cruising gear.
Fuel: 35-gallons (half-full tank)

TEST RESULTS

Upwind into small waves:

SOG   RPM  MPG   LOAD TRIM  NOTES
23.2  3736 2.52  34   35    Not yet optimized for this throttle setting
24.5  3536 2.76  34   36    Optimum fuel economy
27.8  3918 2.66  37   36    Nice cruising speed
29.1  4051 2.66  37   36    Same LOAD as above, but faster speeed
32.9  4456 2.66  41   36    Now 5-MPH faster with same fuel economy
36.5  4921 2.49  46   47    Fast cruising speed
42.6  5605 2.09 100   40    Maximum throttle

Downwind with small waves:

SOG   RPM  MPG   LOAD TRIM  NOTES
28.0  3894 2.77  37   35    Optimum fuel economy
28.0  3793 2.81  36   35    Optimum fuel economy
29.2  3949 2.76  37   36    Optimum fuel economy
29.7  3937 2.84  37   25    Optimum fuel economy--cherry picking the data
35.7  4690 2.61  44   34    Fast cruising speed with minimum effect on economy
35.8  4708 2.63  44   33    Fast cruising speed with minimum effect on economy


Slow speed data
SOG   RPM  MPG   LOAD TRIM  NOTES
2.9   503  10.2  0    35    To burn 1-gallon takes 3.5-hours at this speed

[jimh]

Recently we were underway with the boat very heavily loaded:

• 65-gallons fuel
• a 96-quart cooler packed with ice, beer, and food
• a cabin filled with mattress, sleeping gear, dry goods, clothing, and books and charts for a week of living aboard
• all weather canvas rigged and up
• four adults aboard instead of the usual two adult crew

Best boat speed was reduced to 40.9-MPH. I did not note the engine speed. Fuel economy at best cruising speed was about 2.2-MPG

Later with our two extra passengers gone, and going upwind into moderate headseas, the best fuel economy was only 2.4-MPG.

An hour later heading downwind in smaller following seas, fuel economy was back to a steady 2.6-MPH and 2.7-MPG on occasion.

The boat was at its heaviest loading when this data was collected.

[jimh]

Regarding the heavy-load performance data above: while cleaning the boat after our cruise, I just noticed that while underway last week the aft cockpit live well had about 15-gallons of rain water in it. Add another 100-lbs to the already heavy cruising load.

[jimh]

While running the boat in very light load state, with no canvas up, only 22-gallons fuel, and in very calm seas and no wind, the boat speed hit 44.5-MPH at an engine speed of 5,700-RPM. Fuel economy was also very good, and we saw 2.8-MPG at many boat speeds.

The effect on performance of boat weight, air resistance from canvas, sea state and wind, and other environmental influences continues to surprise me.

[jimh]

I have tested a new propeller, an Evinrude CYCLONE 17 TBX. I had previously tested a CYCLONE 17 propeller and found it to be a good performer. An opportunity arose to buy one at remarkably low cost. The CYCLONE TBX propeller I bought is a newer model that uses the Evinrude TBX hub kit system, and I also wanted to try a TBX hub. I was able to get a TBX hub kit at a very good price, too, so I couldn’t resist the opportunity to purchase and test this propeller.

The CYCLONE 17 TBX propeller is a polished stainless steel four-bladed propeller made by Evinrude specifically for the legacy E-TEC engines. The blades have the typical sharp-edged thick trailing edges. The leading edges are thin but have a smooth and rounded entry. There is a modest rake to the blades. There is the typical blade cup. This particular propeller was previously used but in very good condition. In shipping there may have been a minor nick or two in a blade edge due the hub kit parts becoming loose from their box and rattling around. A few minutes with emery cloth and the blades were all smooth and like new.

The marked pitch is 17-inch (same as the three-blade propeller tested above) and the diameter is 14-1/4-inches, about 3/4-inch less than the three-blade MIRAGEplus propeller. The length of the CYCLONE hub is 6-inches, or 3/4-inch shorter than the three-blade propeller. The exhaust port flares to a 4-3/4-inch diameter, slightly smaller than the three-blade.

Installing the TBX-style propeller took a few minutes. The plastic coupling between the propeller shaft and the long brass splined coupling to the propeller required a bit of work to assemble. I pre-fitted the plastic coupler into the propeller hub as deeply as I could, using a small block of wood and a hammer to seat it. But the coupler was still not bottomed out. Several revolutions of the propeller nut were needed to fully seat the coupler into the tapered square bore of the propeller hub.

Environmental conditions for this test were similar to prior testing: fair weather, high pressure, clear skies, air temperature high-70’s, and water temperature 73-degrees. The wind was 7 to 10-MPH. Waves were 1-foot or less.

The four-blade propeller produced a different engine vibration frequency than the three-blade, as expected. I don't have any measured frequency or amplitude data about the vibration. This summer I have noticed a cockpit coaming panel has had a tendency to rattle in sympathetic vibration with the engine and three-blade propeller. That panel was not excited into vibration by the four-blade.

The boat was in a light weight configuration as before, and fuel was now only 16 to 19-gallons during the test. We did have the Flying Top canvas up.

The first change I noted was the maximum engine speed of the E-TEC was limited to 5,500-RPM, about 100-RPM lower than with the three-blade propeller of the same pitch. This is a reasonable outcome, as in general a four-bladed propeller will be harder to turn than a three-bladed propeller (although the smaller blade diameter will tend to reduce that effect).

Hitting my usual benchmark of 2.7-MPG fuel economy was difficult. I was finally able to coax a reading of 2.7 while running down wind and down sea, and at a boat speed of 27 to 30-MPH.

The maximum boat speed was 42-MPH, again a bit lower than with the three-blade.

Overall, maximum engine speed, maximum boat speed, and maximum fuel economy were all lower than the three-blade propeller.

I did not observe any remarkable changes in the boat’s handling. There may be a slight improvement in controlling the bow rise, but bow rise on a Whaler Drive boat is always very limited in range; the Whaler Drive acts like a giant trim tab and won’t let the bow come up very much.

I will keep the CYCLONE on the boat for the rest of the season and spend more time evaluating it and collecting more data.

Here are two data points.

Evinrude CYCLONE 17 four-blade propeller

For both measurements the throttle position and trim position were
LOAD=36
TRIM=33 to 34

UPWIND
RPM=4000  MPH=28.4  MPG=2.6

DOWNWIND
RPM=3950  MPH=28.5  MPG=2.7

[jimh]

A remark on propeller testing in general

In both reports above, the propellers tested were not new propellers. Both were in like-new condition. Both propellers are products of outboard engine manufacturers, and one might assume, perhaps, that propellers from outboard engine manufacturers are generally high-quality and well-designed for the outboard engines of the specific manufacturer. The prices of propellers from outboard manufacturers are generally higher than for propellers from aftermarket providers.

Even assuming that the two propellers were in perfect, as-new condition, consideration has to be given to the fact that these are mass-produced propellers. They are not delivered from the manufacturer as new in perfect balance with every blade carefully checked and nudged to be in the exact same pitch. Getting a finely-tuned and balanced propeller generally means paying about double the cost of a standard production propeller (or more) for a "lab-finished" propeller. On the basis that the tested propellers are both standard production parts and were slightly used, an assumption that each is an absolute perfect specimen is not justified. Inasmuch as the reported differences in performance are rather slight, to assume that if the tests were repeated with a different pair of these propellers the exact same results would be obtained is probably a risky assumption.

For example, the difference in observed fuel economy is only 0.1-MPG in a value of 2.7-MPG. This is a variance of onl 0.1/2.7 or 3.7-percent. The small difference may a result of testing errors, testing conditions, testing bias, and natural variation in the products being tested, and not due to a fundamental difference in the nature of the two propeller designs. Holding all test variable to be identical and to cause less than 3.7-percent influence on the results is really extremely difficult to achieve, in my opinion, in propeller testing.

The best methods of testing propellers should include blind testing, that is, testing where the boat driver and the person recording the data have no knowledge of what propeller is being tested. The propellers should be tested on the same propeller shaft, on the same engine, on the same boat, and within a few minutes of each other, so that influences due to variations in the engine power output, the hull fairness, weight, and wind resistance, and air and water environmental conditions can be held to a minimum.

A further consideration in propeller testing is the engine fuel. Today the gasoline fuels available vary in their ethanol content, from no ethanol to perhaps 10-percent or more ethanol content. Fuel octane also varies. Engine power output will be affected by the fuel being used. An engine will produce more power output on pure gasoline fuel of higher octane than it will with a fuel consisting of a blend of gasoline and ethanol and lower octane. In order to have comparable test data, the engine fuel should be consistent throughout all tests.

[jimh]

Here is more data on my testing with the Evinrude CYCLONE four-blade 17-pitch propeller:

Performance Data

Propeller CYCLONE 4 17-pitch TBX hub kit, 14.25-inch diameter

TEST CONDITIONS

Date: August 22, 2019
Air Temperature: 74-degrees
Wind: 10-knots to perhaps 15-knot gusts
Current: none
Humidity: unknown, probably 50- to 70-percent, a nice Summer day
Waves: 1-foot or less
Crew: two aboard; total crew weight 360-lbs
Canvas: Flying Top deployed
General gear: normal non-overnight cruising gear.
Fuel: 37-gallons (half-full tank) mostly all fresh REC 90 pure gasoline

Downwind

LOAD=37
TRIM=41
RPM=4078
SOG=29.7
MPG=2.72

LOAD=39
TRIM=36
RPM=4340
SOG=32.5
MPG=2.76

Upwind

LOAD=39 (same as downwind run immediately prior)
TRIM=37
RPM=4288
SOG=31.8
MPG=2.70

LOAD=8
TRIM=55
RPM=1074
SOG=5.4
MPG=6.58

After more time underway with the CYCLONE propeller, the best fuel economy with this propeller seems to occur at a higher cruising speed. Boat speeds in the 28 to 32-MPH range seem to have the best fuel economy in MPG.

We found the propeller had reasonably good reverse thrust at low speeds. We also had to go into reverse and apply a lot of throttle in order to stop the boat very rapidly when we came up on a barely submerged but completely unmarked breakwall. The record-high-water-level in Lake Michigan had completely submerged the rock rip-rap of this breakwall, and we were lucky to be going slowly and could stop in time before running over it.

[jimh]

Since the four-bladed propeller (Evinrude CYCLONE 17 pitch) was installed, the boat has not been run in any significant waves, except for a few miles on the last trip of the season. We were running downwind on Burt Lake, loping along at 28-MPH, riding up and over some two-footers. As in any sea state, there will be occasionally higher waves, and at one point we came over the top of a larger wave. The trough in front of the wave was rather deep, and as the bow of the boat launched off into the air, I was anticipating a rough landing.

To my surprise, the CYCLONE 17 propeller just held the bow steady, and the boat gently settled downward with a rather soft landing. This behavior is also an effect of the E-TEC engine, which just seems to have no limit on torque and never loses any engine speed when the propeller load soars briefly higher. The CYCLONE four-bladed propeller surprised me with how slowly it let the bow come down and how soft the landing became.

I don't have any scientific data to compare the CYCLONE to the three-blade--the other propeller also seems to be able to hold the bow in the air when launching off a wave--but that four-blade did a very nice job of keeping the boat from slamming down hard, and I was a bit surprised by the easy landing that occurred. I was expecting something a bit harsher.

[Jefecinco]

Jim,

Regarding the new propeller, did you notice any improvement in acceleration or time to reach planing speed from idle speed? Was there a noticeable difference in the lowest speed at which plane could be maintained?

[jimh]

BUTCH--I did not notice any easily observed change in time to plane. With either propeller, the boat is on plane in seconds. If there were any change--in either longer or shorter time to plane--I would estimate it would have been very small, maybe a second. The time to plane is really determined by how fast I advance the throttle. The boat shows no reticence to get on plane.

I did not experiment with lowest possible planing speed with the four-blade. The three-blade propeller has already demonstrated that it can keep the boat on plane at about 10-MPH (or less) into big head seas. Next time we encounter some big headsets and have the four-blade still on, I will see how it does.

The ability to keep the boat on plane at a lower speed is more likely NOT related to the propeller, but instead is a function of the engine torque available. Many outboard engines have narrow power bands and just cannot develop enough power to turn a propeller under heavy loads at low pre-planing speeds, where the boat is really traveling uphill on its own bow wave. The E-TEC engine acts more like a diesel engine. It just runs at the speed you set the throttle, and you can make the boat travel at almost any speed you want between displacement speed and planing speed. I don't do that very much, unless conditions demand it, because the fuel economy is not very good in those intermediate boat speed ranges.

Before we put the E-TEC on this boat, its classic two-stroke carburetor 3.0-liter V6 engine could not keep the boat on-plane or on-near-plane at speeds between about 8-MPH and 20-MPH. The classic two-stroke did not have enough torque in the engine speed range needed.

If people report that a new propeller let them keep the boat on plane at lower speeds, it may be because the new propeller is slipping badly, and the engine speed is then higher at that boat speed, and the engine can stay at that speed due to the propeller slip.

Again, I got the four-blade for these reasons:

--I wanted a TBX hub propeller because I felt the TBX hub is a better design than the FLO-TORQ hub I was using;

--the CYCLONE 17 was available at an extremely good price, far below even dealer cost, and about 80-percent off its usual discounted retail price;

--I had been running the same propeller for many years, and I thought, hey, what the heck, let's buy this nice four-blade and fool around with it.

[jimh]

In looking over my notes from the test of the CYCLONE 17 propeller, I found the top speed was 42.0-MPH. The top speed with the MIRAGEplus was 42.6-MPH, or slightly faster. In assessing the propellers, it should be noted that the mounting height that was used might not have been quite the same for both propellers due to their difference in diameter, even thought the engine mounting was not changed.

The MIRAGEplus propeller is a 15.5-inch diameter propeller. The CYCLONE is 14.25-inch diameter propeller. The blade tips of the MIRAGEplus will then be 7.75-inches from the propeller shaft, while the blade tips of the CYCLONE will be 7.125-inches. This is a difference 0.625-inches, or almost 3/4-inch. The waterline running over the engine gear case is going to be the same with either propeller, and the location of the propeller shaft is going to be the same, so the result of running the CYCLONE at the same engine mounting height as the MIRAGEplus will be to locate the propeller tips of the CYCLONE blades 0.625 farther below the water surface than the blade tips of the MIRAGEplus, or, in other words, the CYCLONE was running about one-hole deeper as measured by the blade tip position than the MIRAGEplus.

A more fair comparison might be achieved if the engine mounting were raised one-hole so the CYCLONE blades were operating about the same depth under the water as the MIRAGEplus blades. This is a subtle consideration, but before writing off the CYCLONE propeller as being slower, one ought to test it at the equivalent immersion depth as considered by blade tip position.

[jimh]

Here is more recently obtained data on my testing with the Evinrude CYCLONE four-blade 17-pitch propeller. The engine in all these tests is the same engine, the 2010 E-TEC 225 3.3-liter V6 engine. The tests are reports of variations due to propeller changes.

Performance Data

Propeller CYCLONE 4 17-pitch, 14.25-inch diameter

TEST CONDITIONS

Date: August 24, 2020
Air Temperature: 79-degrees
Water Temperature: 74-degrees
Wind: calm
Current: none
Humidity: muggy, probably 70-percent or more
Waves: ripples
Crew: two aboard; total crew weight 360-lbs
Canvas: None deployed
General gear: minimal
Fuel: 37-gallons (half-full tank) mostly all fresh REC 90 pure gasoline
Engine Mounting Height: unchanged; still one-hole up on Whaler Drive

Upwind

LOAD = 100
TRIM = 33
RPM = 5480
SOG = 43.5-MPH
MPG = (Not recorded)
SLIP = 8.2% calculated

The full-throttle engine speed of 5480-RPM was just below the narrow range specified as optimum, 5500 to 5700, for this E-TEC engine, but well within the recommended operating range of 4500 to 5800-RPM.

The warm and muggy air and the very warm water may have affected performance. Engines produce more power in colder dryer air and propeller efficiency improves in colder water.

The calculated SLIP at 8-percent is a good indicator the propeller is working efficiently.

Trimming out beyond the usual TRIM = 33 tends to result in the bow bouncing when the weight forward is really light, as it was in this test. Boats with a Whaler Drive just don’t run on plane with the bow very high.

[jimh]

Another difference between three-bladed and four-bladed propellers is the vibrations created when a propeller blade is aligned with the skeg and gearcase or shadowed by them. In that position the water flow is disrupted and the blade loading on that propeller blade changes. This produces a vibration.

Assume the engine speed is 1,000-RPM and the gear ratio is as above, 1.86:1. The propeller shaft speed is then

1000 / 1.86 = 537.6-RPM

Converting to revolutions per second

537-revolutions/1-minute x 1-minute/60-seconds

8.96 revolutions-per-second

With a three-bladed propeller there will be six occurrences of a blade being shadowed per revolution. A three-bladed propeller at 1,000-RPM engine speed thus generates a vibration with a frequency of

6 x 8.96 = 53.76-Hz

With a four-bladed propeller there will be four occurrences of a blade being shadowed per revolution. A four-bladed propeller at 1,000-RPM engine speed thus generates a vibration with a frequency of

4 x 8.96 = 38.4-Hz

There is also a difference in the amount of propeller blade that is shadowed. With a three-bladed propeller only one blade of three or one-third of the blade area is shadowed at a time. With a four-bladed propeller two blades of four or one-half the blade area is shadowed at a time. Because a larger portion of the blade area is being shadowed in the four-bladed propeller compared to the three-bladed propeller, the intensity of any vibration might be greater in the four-bladed propeller.

Another factor, however, may be affecting the vibration. With a four-bladed propeller the blade shadowing is symmetrical as both the top blade and bottom blade are shadowed at the same time. With a three-bladed propeller each blade of the three blades passes through the shadow of the sketch and gear case separately, creating six different directions of offsets.

The net effect of all these influences is a difference in the frequency and strength of a vibration created by the propeller blades being shadowed. How this will affect a particular boat will depend on many factors, and to predict that one style propeller will reduce vibration on any particular boat and engine combination at any particular engine speed will be difficult to impossible.

[jimh]

Got another data point on September 11, 2020, for the CYCLONE 17-pitch four-bladed propeller on a late summer day with 64-degree air and 62-degree water. The boat was lightly loaded as in prior data runs.

Tweaking for best MPG at fast planing speeds, i again found this boat-engine-propeller combination would produce 2.7-MPG at 29 to 32-MPH.

TRIM was about 35, and
LOAD (percent of full throttle) was 37.

The data was taken down wind in very light wind and with ideal conditions with just a ripple on the water surface.

[jimh]

On the last day of boating for me in 2020, a new top speed was set for my 1990 REVENGE 22 W-T Whaler Drive boat with 225-HP E-TEC. Still using the four-bladed CYCLONE propeller with 17-pitch, the GNSS receiver showed a speed over ground of 45.4-MPH. This new high speed mark was assisted by the lack of any canvas being up, having no gear aboard, just the usual crew of two, fuel at half-full, cold air temperature at 45 to 48-degrees, water temperature about 55-degrees, no wind, no waves, and possibly a very small favorable current. We were running in a river, but at a point where the river widens considerably and creates a large marsh.

Engine speed was 5,650-RPM. That calculates to a SLIP of 7.7-percent. On that basis I find this data set quite reasonable to accept.

The factors which I feel had the most influence in the new top speed were:

• cold air
• cold water
• light load
• no canvas
• very calm water allowing a long wind up to maximum speed and hull trim adjustments

I did see a value of 45-MPH on the instrument panel, but in the trip log for that day I found the 45.4-MPH value was the highest recorded. We did make a run in the opposite direction, and the top speed for that one was over 44-MPH. I did not make a note of the exact speed value.

[jimh]

I put the old-favorite Mercury MIRAGEplus three-bladed 17-pitch propeller back on the boat, and made several test runs to establish new data for it. One interesting note: the engine had just burned about 55-gallons of fuel that was treated with the BRP Evinrude FUEL SYSTEM CLEANER product. This produced a noticeable amount of soot in the exhaust, which was taken as an indicator that some carbon deposits in the engine had been cleaned away by use of this fuel additive. Here is the test data:

BOAT, ENGINE, PROPELLER
Boat: 1990 Boston Whaler Revenge 22 W-T Whaler Drive

Engine: E-TEC 225, Evinrude, 2010-model-year, E225DPXISE
Recommended WOT RPM Range: 4500 to 5800-RPM
Optimum WOT RPM Range: 5500 to 5700-RPM
Gear ratio: 1.846:1 [corrected from 1.86 originally]
Mounting height one-hole-up on Whaler Drive

Propeller: Mercury MIRAGEplus 17-pitch three-blade stainless steel PN 48-18278
Diameter 15-1/2-inches
Length 6-3/4-inches
Exhaust port flare diameter 4-7/8-inches

TEST CONDITIONS
Location: Northport Bay, Lake Michigan
Date: August 16, 2021
Air temperature 75-degrees-F
Water temperature 72-degrees-F
Current: none
Waves: less than one-foot
Wind: 10-knots
Barometer = 1018 millibars; high pressure

Crew: two aboard
Canvas: Flying Top deployed
Fuel: 23-gallons
Gear: typical non-cruising gear

TEST RESULTS

DIRECTION SOG   RPM    MPG   LOAD  TRIM  SLIP
Upwind    23.2  3725   2.45  35    29    23.2
Downwind  25.4  3600   2.8   35    29    19.1
Upwind    27.1  3775   2.73  36    35    17.7
Downwind  27.3  3800   2.77  36    33    17.6
Downwind  27.0  3750   2.8   35    35    17.5
Downwind  44.0  5850               60    13.8

NOTES

The full-throttle engine speed of 5,800-RPM was the highest engine speed observed in a long time. The accompanying boat speed of 44-MPH is equal to the best-ever boat speed. The engine trim was higher than normal. This was done in an attempt to reduce the oscillation of the bow. I believe the Whaler Drive tends to act as a giant fixed trim tab, and limits the bow rise. I was using a lot of trim-up in order to try to keep the bow up, and reduce the oscillations. This was not successful. With the Whaler Drive the boat just seems very unstable above about 35-MPH due to the bow tending to oscillate. I probably should have use less trim-up.

The relatively high SLIP number calculated suggest that perhaps the engine mounting height might be too high, or that, as often observed, the propeller runs in aerated water with a Whaler Drive single-engine rig.

[jimh]

I note that in an earlier test with a four-blade CYCLONE 17 propeller, the calculated SLIP was quite a bit lower, only 7.7-percent, compared to the three-blade MIRAGEplus 17-pitch with 13.8-percent SLIP, at the same 44-MPH boat speed.

One factor to consider is the propeller diameters. The three-blade is a 15-inch diameter propeller and the four-blade is only a 14.25-inch diameter. The difference in diameter means the blade tips of the three-blade run closer to the water surface than the blade tips of the four-blade (for the same engine mounting height).

Also in the three-blade test I had the engine trimmed out farther. Those two factors are likely to have influenced the SLIP calculated value.

A third factor: the three-bladed propeller has only very slight blade rake, so it is more of a stern-lifting propeller than the raked four-bladed propeller. If there were more stern lift with the three-bladed propeller, that would also move the blade tips of the three-bladed propeller closer to the water surface and into more aerated water. That would also tend to increase SLIP.

What I am seeing and learning: there are many subtle factors that influence propeller performance. It's not just a pitch number that determines what happens.

[jimh]

We have had perfect boating weather for seven days in a row, and to not take advantage of this stretch of fair, warm, sunny, days with no winds or waves was impossible. We had to get out on the water. Rather than just cruise aimlessly around, another propeller was tested.

On the last trip I carried a different spare propeller than usual: an old OMC three-bladed steel propeller with 15-inch diameter and 15-pitch, a so-called square wheel propeller. About a decade ago or longer, I often ran this propeller on the boat when the engine was a 1992 Evinrude V6 carburetor engine. When the boat was heavily loaded for cruising, it seems like a very good propeller for the boat-engine combination. I don't recall any test data for this propeller on the E-TEC 225-HP engine, and if I was going to carry it as a spare I should have some idea of how it would work. A test was called for on that basis.

BOAT, ENGINE, PROPELLER
Boat: 1990 Boston Whaler Revenge 22 W-T Whaler Drive

Engine: E-TEC 225, Evinrude, 2010-model-year, E225DPXISE
Recommended WOT RPM Range: 4500 to 5800-RPM
Optimum WOT RPM Range: 5500 to 5700-RPM
Gear ratio: 1.846:1 [corrected from 1.86 originally]
Mounting height: one-hole-up on Whaler Drive

Propeller: OMC SST-II three-blade stainless steel propeller, rubber hub, PN 174926
Pitch 15-inches
Diameter 15-inches
Length 7-1/8-inches
Exhaust port flare diameter 5-1/2-inches

TEST CONDITIONS
Location: Northport Bay, Lake Michigan
Date: August 19, 2021
Air temperature 88-degrees-F
Water temperature 75-degrees-F
Current: none
Waves: ripples
Wind: 5-knots
Barometer = 1018 millibars corrected to sea level; high pressure

Crew: two aboard
Canvas: Flying Top deployed
Fuel: 18-gallons
Gear: typical non-cruising gear

TEST RESULTS

DIRECTION SOG   RPM    MPG   LOAD  TRIM  SLIP
--         5.5  1030   7.8   07    35   30.6
--        24.8  3850   2.53  35    23   16
--        27.5  4160   2.51  36    33   14.1
--        29.8  4450   2.58  38    33   13.0
--        31.6  4670   2.57  40    33   12.4  
--        36.2  5275   2.32  48    33   10.8
--        35.5  5100   2.10  48    36    9.5
Downwind  41.1  5900   2.0  100    35    9.5

NOTES
With this 15-pitch propeller the boat responds to any throttle movement immediately. The engine acts like there is really no load, no burden on the engine to prevent it from accelerating. The most significant difference noted was the fuel economy seemed to peak at 2.5-MPH, with one reading close to 2.6-MPG. For a wide range of boat speeds, the fuel economy remained at 2.5-MPG. That included at a slow planing speed of 22-MPH, which can often be a nice speed to run in waves.

I bought this propeller used--probably very used--for $50 many years ago. Other than the slightly lower fuel economy compared to the much more modern and much more expensive MIRAGEplus, this old OMC is a versatile and useful propeller.

All the test data was collected without regard to wind or waves because both very very small, but the full-throttle run was the last of the day, after about an hour of just boating around, and the run was done farther offshore so there were some small waves. We were going down sea and down wind on that run. I don't think we hit the rev-limiter; 6000 RPM was the most shown on the digital tachometer.

With this propeller, the boat seems to run just fine with one trim setting: TRIM = 33. That is a nice characteristic because the helmsman does not have to play with the engine trim for each new boat speed setting.

Chris made a cogent comment: the engine sounds louder with this propeller. I think more engine exhaust is breaking through to the water surface with this propeller compared to the other recently tested propellers. Perhaps that wide exhaust diffuser at the end of the propeller hub is responsible.

[jimh]

The next iteration in propeller testing was to install a SOLAS RBX-100 hub kit to replace the Mercury FLO-TORQ II hub kit that had been in use for many years with the Mercury MIRAGEplus propeller. The purpose of that change was to reduce the propeller shifting CLUNK. I offer more comments on that in a separate article. While out testing for the noise change, some additional performance data was also recorded.

Performance Data
BOAT, ENGINE, PROPELLER

Boat: REVENGE 22 Walk-Through Whaler Drive, 1990

Engine: E-TEC 225, Evinrude, 2010-model-year, E225DPXISE
Recommended WOT RPM Range: 4500 to 5800-RPM
Optimum WOT RPM Range: 5500 to 5700-RPM
Gear ratio: 1.846:1
Mounting height: one-hole-up

Propeller: Mercury MIRAGEplus 17-pitch three-blade stainless steel PN 48-18278
Diameter 15-1/2-inches
Length 6-3/4-inches
Exhaust port flare diameter 4-7/8-inches
PVS Vents: Closed
Hub kit: SOLAS RBX-100

TEST CONDITIONS
Date: August 30, 2020
Air Temperature: 75-degrees
Water Temperature: 74-degrees
Wind: light to calm
Current: none
Humidity: low, probably not more than 50-percent
Waves: ripples 
Crew: two aboard; total crew weight 360-lbs
Canvas: Flying Top deployed
General gear: minimal
Fuel: 15-gallons mostly all fresh REC 90 pure gasoline
Engine Mounting Height: unchanged; still one-hole up on Whaler Drive

TEST RESULTS

WIND    RPM   MPH   TRIM LOAD  MPG    SLIP
Cross   3440  24.2  26   35    2.75   18.7
Upwind  3675  26.7  32   35    2.81   16.7
Cross	3930  29.9  31   38    2.76   12.8
Down    4485  34    31   42    2.68   13.1
Cross   5650  43.5  35  100    2.1    11.7

There is nothing particular unusual about the engine speed, boat speed, and fuel economy numbers in the above data, except that in the full-thottle test the engine trim was kept lower than in the last testing. This produced a lower SLIP calculated value with slightly lower boat speed (0.5-MPH less) and slightly lower engine speed (200-RPM less). The boat was rather light in this test, and we occasionally saw 2.8-MPG numbers, but not steadily.

The MIRAGEplus three-bladed 17-pitch has continually delivered the best fuel economy of any propeller tested except for the Evinrude REBEL, a very similar, three-bladed large-blade-area, moderate-blade-rake propeller. I would not mind re-testing the REBEL 16 or REBEL 17, but to buy one might require a substantial investment, and I am quite satisfied with the MIRAGEplus results.

In some correspondence with SOLAS (the makers of the hub kit) they noted that in their RUBEX propeller line the propeller most similar to the Mercury MIRAGEplus would be their stainless steel three blade L4 propellers, #9571-155-17 (3-blade x 15-1/2-inch x 17-pitch in RH) or #9571-158-15 (15-3/4-inch x 15-pitch in RH}.

[jimh]

The 2010 E-TEC 225-HP engine on my REVENGE 22 W-T Whaler Drive boat is now beginning its 15th boating season; the first season was in July 2009. Chris and I went for a two hour lunch cruise in Northport Bay on June 22, 2023, the first full day of Summer. I did not gather complete performance data, but I did check a few important bench marks.

ENGINE SPEED AT FULL THROTTLE = 5,900-RPM
BEST FUEL ECONOMY AT CRUISE = 2.8-MPG at TRIM=33 and LOAD=35; boat speed 25 to 26-MPH
BEST BOAT SPEED = 43.5-MPH with TRIM reduced to suppress bow oscillating
ENGINE TEMPERATURE AT 500 to 900-RPM = 160 to 175-degrees-F

The propeller was the Mercury MIRAGEplus 17-pitch. The gasoline fuel was from September 2022. The boat was lightly loaded: 35-gallons of fuel, Flying Top erected, no cruising gear aboard.

All the test results were essentially identical with previous performance tests, which I interpret as indicating there was no harm to the engine in its eight month layup in indoor unheated storage that began in October 2022. The E-TEC is still running like a new engine.

[jimh]

On Saturday, August 19, 2023, we had to cross the width of Lake Huron from Detour in the Upper Peninsula to Cheboygan in the Lower Peninsula, a trip of 39.7-miles dock to dock. Our 1990 REVENGE 22 W-T Whaler Drive was loaded more heavily than usual, as we had the cabin stuffed with gear for sleeping aboard, two coolers on the deck with lots of water and ice, the fuel tank was about 3/4-full at the start, or about 48-gallons, and more spares than normal; in short, the boat was probably several hundred pounds heavier that when we are just out for a day of boating.

The first ten miles of the crossing were into the remnants of a big swell from very strong winds a day or two earlier, and we could run on plane at the usual 27-MPH to 28-MPH, usually the optimum fuel economy speed. Normally the engine would be producing 2.6 or 2.7-MPG, but with the extra weight, fuel economy was down to maybe 2.4-MPG or 2.5-MPG. The farther offshore and into the central part of Lake Huron we traveled, the bigger the swell became, now mixed with wind waves at a 90-degree angle. With those waves I had to reduce boat speed to about 21-MPH to restore a comfortable ride; otherwise, when a set of three or four larger than normal swells rolled up, the boat bow was really slamming hard. The hull was molded 33-years ago, so I prefer to make life easier on the hull--and easier on me and Chris--by giving up speed and fuel economy in favor of comfort.

Eventually as we passed the two-thirds point of the trip, we got into a lee from Bois Blanc Island, and the swell reduced greatly. Now we just had mostly wind waves, but some of them were large enough to rattle the boat on landing.

I wanted to raise the bow and to try to keep up the bow, so the waves would be hitting the keel further back from the bow stem and the hull would be skipping over the wave tops. But with a Whaler Drive hull, you can never get the bow very high no matter what engine trim, as the Whaler Drive acts like a giant trim tab, holding the bow rise to a very modest amount. Also working against me on this trip was all the extra weight in the cabin. As a result, a lot of engine trim was needed to get the bow to come up at all. I finally found an engine trim setting that gave me the ride I wanted, and the fuel economy was actually rather decent, 2.4-MPG, considering we were loaded, going into the wind, going into waves. I jotted down some data for later computation. Here is a snap shot:

MPH = 29.1
RPM = 4600
TRIM = 68 (A 68 setting is very high trim; normal trim is 33; 0 is lowest engine trim, and 100 is maximum up-trim range before tilt takes over.)
MPG = 2.4
GEAR RATIO = 1.845:1.
BOAT SPEED = 29.1-MPH

Putting this data into the Propeller Calculator produces a calculated SLIP of 27.5-percent. I am not surprised at that figure. TRIM at 68 is very high, but that was what was needed to keep the bow up.

The overall average fuel economy for the whole 39.7 miles was also 2.4-MPG. We had two stretches of slow speed operation where the engine would produce 5-MPG or higher, which helped the average somewhat. At some low speed planing segments, the fuel economy was down to 2.0-MPG for a while.

[jimh]

This Fall we had a chance to run the boat in a very light configuration, with all the non-essential gear removed. I was pleased to see that the optimum fuel economy was back to the 2.8-MPG figure recorded in testing ten years ago, and occasionally peaking around 2.85-MPG.

Also, I briefly pushed the throttle to full, and the engine accelerated to more than 5,800-RPM, with further engine speed coming if permitted to continued. I then I pulled back the throttle to a lower setting. This confirmed to me that the propeller selection (MIRAGEplus 17-pitch) was a good choice. Quite some time had elapsed since I last saw that fuel economy and engine speed, as normally the boat has more weight aboard in the form of cruising gear.

We were out for a short spin to introduce fuel that had been treated with fuel conditioner into the entire fuel system. Because an E-TEC engine, even a 3.3-liter V6 engine, will run at idle speeds with a fuel consumption of about 0.2-GPH, it would take ten hours of running the engine at idle speed to draw up two gallons of treated fuel from the fuel tank to the engine. I wanted to consume about two gallons of fuel to be sure that the treated fuel in the fuel tank would reach the engine and all fuel lines in the engine, before performing the unique E-TEC self-winterization procedure at the launch ramp, where we would load the boat on the trailer for eight months of storage until 2023. The only expedient way to to this to run the engine a much faster speeds that idle. With the boat getting at least 2.5-MPG when on plane, we had to go for at least a five-mile run to consume two gallons.

The final 2023 season fuel purchase was made a $5.70-per-gallon, which was probably the highest cost for pure-gasoline 90-Octane fuel being charged all year at the marina fuel dock. We added 22-gallons to get the fuel tank level above HALF-FULL at about 42-gallons (in a 77-gallon tank) for winter storage.

I do not subscribe to the theory that diurnal temperature change can turn a vented fuel tank into a water making machine, but I do like the idea that next Spring I can put the boat back in service and won't have to immediately go to the fuel dock. Also, the way fuel prices have been trending, the cost of marine gasoline fuel at a fuel dock will probably be higher next year than now.