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
TRIM=33 to 34
RPM=4000 MPH=28.4 MPG=2.6
RPM=3950 MPH=28.5 MPG=2.7