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  Propeller Test: Revenge 22 W-T WD: More Data

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Author Topic:   Propeller Test: Revenge 22 W-T WD: More Data
jimh posted 08-28-2006 11:05 PM ET (US)   Profile for jimh   Send Email to jimh  
Recently I had several days available for some boating and the chance to conduct more propeller testing. As I reported previously, I have tested eleven propellers on my boat, a 1990 Boston Whaler REVENGE 22 Walk-Through Whaler Drive with a single 225-HP Outboard, a 1992 Evinrude 225-HP V6.

This second set of testing represents a very narrowed field of propeller candidates, only four propellers. One of the propellers has been used extensively with the boat for over 1,000 miles of operation, and this was the baseline of performance against which the other three were to be measured. The tests were conducted in similar conditions, but not under precisely controlled conditions. The wind and wave conditions were different, but the boat load and water temperatures were similar. Each propeller was used for about half a day of boating in order to get a feeling for how it worked.

An additional reason for re-testing some propellers was an improvement in the engine's performance. Over the course of the spring and summer I have been able to work out a gremlin in the engine which was holding down performance a bit. With the engine producing more power than ever, it was evident that the baseline propeller might be a bit low in pitch. The engine could easily wind this propeller to 6,000-RPM. The baseline propeller is a 15-inch pitch propeller. The three other propellers tested are all marked as 17-inch pitch propeller. It was hoped that the engine could now turn these propellers to higher engine speeds than previous tests had produced.

The test method was to run the boat at various cruising speeds and to record the fuel economy. Fuel economy was measured with a NAVMAN 3100. For each propeller a number of speeds and fuel flow rates were recorded. This data is presented below in graphical form. This presentation will give you the best feel for the performance of the propellers in terms of how efficiently they moved the boat.

I have intentionally masked the model numbers of the propellers in order to prevent that from influencing the interpretation of the results. Here are some observations about the propellers other than the data on fuel:

PROPELLER A: This is the baseline propeller. It has been used extensively. It showed no signs of any ventilation and was able to be trimmed up to give more bow lift when needed. In general I am satisfied with this propeller's performance, except it does not give the greatest fuel economy, particularly at lower cruising speeds in the 22 to 26 MPH range. This propeller can be spun to 6,000-RPM. Top speed was about 39-MPH in calm conditions.

PROPELLER B: This propeller showed a slight tendency toward ventilation, and it had a strange tendency to lose grip then get it back when running in some seas around 25-MPH. This would cause the engine speed to hunt up and down. It could not be run with as much trim out as the baseline propeller. The fuel economy is clearly better in the lower cruising speed range. The top speed was 39-MPH at 5,500-RPM (in some waves).

PROPELLER C: This propeller also showed a tendency toward ventilation. It did not have good slow-speed performance. The propeller seemed to have a lot of SLIP and thus the fuel economy suffered at lower speeds. The propeller did hit a sweet spot around 28-MPH, but this is often a cruising speed which is too fast for wave conditions. Thus, overall, the poor fuel economy at lower cruising speeds was judged to be a significant handicap for this propeller. It hit 40-MPH at 5,600-RPM (in calm water conditions).

PROPELLER D: This propeller showed quite a sensitivity toward ventilation and had to be run with the engine trimmed quite low. The cruising speed fuel economy was excellent between 25 to 32-MPH. This propeller was also the fastest, 40.5-MPH, although the engine could only turn it to 5,200-RPM.


ANALYSIS:

Propeller D produced the best fuel economy and was also the fastest. However, it had a marked tendency toward ventilation with any trim. This propeller may be re-tested under other conditions to see if this is a problem in running the boat. It also held the engine speed down to a point where there was some concern about being over-propped.

Propeller C had a lot of ventilation and slip at lower speeds. It had the most trouble getting the boat on plane. The cruising speed fuel economy was not encouraging. It was on par with the baseline propeller. Since the baseline propeller showed much better boat handling characteristics, this propeller was judged unattractive for this application.

Propeller B gave handling which was the most similar to the baseline propeller, although it too could have ventilation if the trim was set too high. The fuel economy was clearly better than baseline, and nearly as good as or even better than Propeller D at cruising speeds.

At the conclusion of the testing, I put propeller B back on the boat. I will run the boat for another weekend with this propeller to see how it works.

I would be glad to hear any comments about these results. Based on the fuel data, which propeller would you think the optimum?

Perry posted 08-28-2006 11:26 PM ET (US)     Profile for Perry  Send Email to Perry     
jimh, you imply that the propeller is turning at a given RPM. How do you determine this?

If chosing a propeller based fuel economy alone, propeller D would be the obvious choice. Overall handling is important to me. I wouldn't run a prop that had a tendency to cavitate or ventilate so propeller B would be my choice.

Are all the propellers you tested made of stainless steel?

jimh posted 08-28-2006 11:37 PM ET (US)     Profile for jimh  Send Email to jimh     
All the propellers are stainless steel.

The engine speed was probably different for every data point plotted. I don't really care about the engine speed, as long as the fuel economy is good. That is why I have not presented any data about the engine speed, other than to mention the wide-open-throttle speed so the match of the propeller to the engine can be judged.

jimh posted 08-30-2006 08:10 AM ET (US)     Profile for jimh  Send Email to jimh     
Consider the difference in the efficiency of these propellers in this light:

If you run propeller A at around 22-MPH you get 1.7-MPG, and if you run propeller D at around 31-MPH you get 2.15-MPG. Flip this into gallons-per-mile and the figures become 0.588 and 0.465, respectively. That is a difference of 0.123 gallons per mile. Let's say we are in Charlevoix and plan to run out to South Fox Island and back. That will put about 65-miles under our keel. If you run out there with propeller D you'll burn 8-gallons less fuel than if you used propeller A. The price of gasoline at the marina is probably around $3.40/gallon, so the difference in cost is $27.

According to my NAVMAN 3100, we've run about 1,100 miles with our boat in the last two seasons of boating. If we had been able to optimize the propeller choice to produce an improvement of 0.123 gallons-per-mile, we would have saved 135 gallons of gasoline!

Peter posted 08-30-2006 08:25 AM ET (US)     Profile for Peter  Send Email to Peter     
Jim -- Your consideration of efficiency assumes that you are able to run at any speed at any time which is rarely the case in my experience in my waters unless running very early in the morning when there is little wind.

On my 27 I am not running propellers that have the highest peak fuel efficiency or that are the fastest, but rather propellers that provide the greatest ride comfort and provide the best traction in rough conditions. The propellers that provided the highest peak fuel efficiency at the usual cruise speeds produced some of the worst handling and poorest fuel economy in rough conditions due to lack of traction. I essentially traded about 0.1 to 0.2 MPG of fuel economy in easy conditions for the ability to run more comfortably and more efficiently in the rough conditions. I also significantly gained in docking speed control. Like everything in boating, there are numerous trade offs to be made.

I too would pick propeller B from that group based on your description and the graph as it seems to give the most well rounded performance, particularly in the ideal cruising speed range of 25 to 30 MPH. Somewhat below that it still seems to provide good traction in the conditions you ran.

jimh posted 09-06-2006 09:00 AM ET (US)     Profile for jimh  Send Email to jimh     
I am just back from four more days of boating with a little propeller testing thrown in for good measure. More observations:

We ran the boat for two days with the 17-inch pitch OMC SST propeller. The improved fuel economy of the propeller was again observed. We ran the boat in a variety of sea conditions, including going upwind into some 2- to 3-foot waves and in some confused seas around a channel entrance or inlet. The propeller performed fairly well, but its ability to maintain a good bite or grip on the water came into play. In these rougher conditions, the propeller was very sensitive to trim angles. Often it was desirable to run the boat with some bow-high trim, but there was a limited range in which the propeller would hang on. The propeller would tend to break loose into a mode where there was still good thrust but less solid bite. This would make the engine speed run up about 300 to 500 RPM, although the boat speed would remain constant within a mile per hour. On one long 25 mile run with generally following seas, this got to be a bit annoying. Listening to the motor change pitch and speed as the boat worked over the waves seemed to become an irritating noise. I also wondered if the constant load shifting on the motor was doing it any good.

After two days, I changed back to my old reliable, the 15-inch pitch OMC SST. We went off on a 70-mile boat ride, again in a variety of conditions. This propeller just hung on in all winds and waves and all trims. It never broke loose. The fuel economy was not as good, but the handling was excellent. The propeller can be trimmed up to give some lift to the bow, and it shows no sign of breaking loose.

I must mention that both of these propellers are older propellers and have had a lot of use before I got them. They are by no means in new condition, and it may not be appropriate to draw conclusions about the newest Bombardier propellers in this series from my observations about these old props. When I was changing propellers on Sunday morning at the dock, I had the two SST's sitting side by side, and, after making a very close inspection of the blades of each of them and enhanced by the strong sunlight illuminating them, I finally noticed that there was a subtle difference in the blade shape.

The trailing edge of the blades on the 15-inch propeller had been re-worked at some point to add more cup to the blade along the trailing edge of the blade near the hub. Both propellers had some cup on the blade tips, but only the 15-inch propeller had this cup near the root. And there were some marks and scratches which could be seen which seemed to show this was added to the propeller after it was cast in the mold. I had never observed this before, and it was quite a surprise that such a subtle difference in blade shape could make such a big difference in the way the propeller behaved.

Getting the right propeller on a boat makes all the difference. Through this long propeller testing process I am learning what my boat needs and what different propellers have to offer.

The identity of the propellers:

--A = 15-inch pitch OMC SST three-blade
--B = 17-inch pitch OMC SST three-blade
--C = 17-inch pitch OMC OFFSHORE four-blade
--D = 17-inch pitch Mercury MIRAGEplus

jimh posted 01-21-2007 01:48 PM ET (US)     Profile for jimh  Send Email to jimh     
More follow up on the propeller testing.

In late September we took the boat south for a week of boating on Tennessee's Watts Bar Lake. The water temperature was quite warm, around 72-degrees, and air temperatures were in the low-80-degree range. The wave conditions were generally calm or very small wind waves, less than one foot.

When we launched the boat, Propeller A (OMC SST 15) was still on the engine. Its performance is well documented. After moving the boat to our dock, we changed to Propeller B (OMC SST 17), anticipating its better fuel economy would pay dividends.

In the calm water of the river, Propeller B performed beautifully. There was no problem with loss of grip due to ventilation. The engine could be set to the desired trim without causing propeller ventilation and loss of efficiency. The boat was carrying less weight, particularly in the cabin. As opposed to prior tests where the cabin held several hundred pounds of bedding, clothing, and gear, during these tests there was little extra weight in the cabin. This may have helped the boat's general trim, eliminating a tendency for the static trim to be completely even or even slight down by the bow. This in turn may have affected the propeller performance.

With the boat running lighter, the top speed with Propeller B increased to over 41-MPH as measured running against a minor river current in an arm of Watts Bar Lake.

After returning north, Propeller B was tested again for top speed on a small inland lake. The water and air temperatures were in the low-50-degree range. In these conditions, we hit an new all-time speed record for CONTINUOUSWAVE of 42.5-MPH and an amazing fuel economy of 2.5-MPG, which would be off the chart (literally) on the plot above.

Based on these experiences, it looks like the optimum propeller varies with many factors, including:

--boat weight and weight distribution
--air and water temperature
--wave conditions

When conditions allow a higher pitch to be used, it is possible to enhance the fuel economy significantly, that is, by as much as 20 to 25 percent. With the high price of fuel we have encountered (as much as $4.22/gallon), it may be well worth the effort to change the propeller to match the conditions in order to improve fuel economy to its maximum. A reduction of fuel costs of 25-percent when prices are at the $4/gallon range amounts to a one dollar per gallon savings.

Swellmonster posted 08-14-2009 10:50 PM ET (US)     Profile for Swellmonster  Send Email to Swellmonster     
How do your trim tabs effect your data? Obviously more drag changes things
When I have used a 15 rev 4, I found that the transom had so much lift that I really didnt need tabs..
With the 15, I could pull a 300 foot barge, great tork and ultimate response..
Tom W Clark posted 08-15-2009 12:15 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Pat -- You've resurrected the thread that is two and a half years old.

Continuouswave does not have trim tabs.

jimh posted 08-15-2009 08:40 AM ET (US)     Profile for jimh  Send Email to jimh     
At the time I tested the REVOLUTION4 propeller it was not being made in a 15-inch pitch. I tested the lowest pitch available, 17-pitch. The test occurred early in my propeller testing, and at that time the motor had a few running problems, and the power output of the motor was probably not as great as in later tests, after I had made some repairs and improvements to the motor.

The REVOLUTION4 is not one of the four propellers tested in this report. However, I would like to try a REVOLUTION4 again, if one becomes available for a test run. Should that occur I will append new data about the test to the main article or perhaps begin a new one. Since this thread was begun, I have changed the motor on the boat. I expect do have some new propeller test data to report when I get a chance to collect the information from testing.

The comments about stern lift from the REVOLUTION4 are interesting. Thank you.

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