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Author Topic:   E-TEC, Revolution4 and Enertia Propellers

pineapplepig posted 01-01-2007 01:53 PM ET (US)
Even though my Edgewater 245 is not a Whaler, it is a Dougherty-designed hull and I see it as the same. My experience with my Edgewater may be of interest to Whaler owners when it comes to props. Forgive me, but this is going to be a long post. [Heck--we love long posts, if they are like this one and filled with information--jimh.]
Well, finally got the time to try out my new Edgewater 245 which I have hung with twin 200 small bore 2.6-liter E-TEC motors. I was not impressed with the relative lack of performance of the standard Yamaha 150-HP motors the boat comes with from the factory. Also the E-TEC motors really set the boat off with their sharp design. What might be of interest to others in this report is the limited difference in performance with the addition of an extra probably 70-HP--apparently the standard fit Yamaha 150-HP motors put out about 165-HP--but what cannot be really explained here is the difference in hole shot, acceleration, and overall feel, which is truly electric. I have also been evaluating the difference between Mercury REVOLUTION4 and ENERTIA propellers
First off, the E-TEC motors: So far I am delighted with them. They are smooth, quiet, very responsive, and when you are pushing them they make a really exceptional turbine-like howl. Fuel economy is great, I think over 2.5-MPG for 12 cylinders is pretty good on a 6,000-lb boat. Oil usage a non-event. Exhaust smell absolutely zero. And for trolling never a hint of exhaust and [fuel burn] under a gallon an hour for the two motors. I do suspect that if you want the full top end that 400-HP would suggest, then you have to go to the 3.3 big block with the torque to run the propellers higher up the range. But then that is just too much weight on the stern. In short, there is no substitute for displacement, but then BRP are squeezing a lot out of a small package. Maximum power is produced at 5,250-RPM and the powerband is 4,650 to 5,850, so according to BRP I am in right zone.
Below I post the results as best as I was able to evaluate in less than ideal circumstances and I should say this is my first effort at recording and posting comparative figures. Figures are for both motors. Boat weighed well over 6,000-lbs with full fuel, power assisted steering, full water, full fishing gear, spare anchors, T-Top, loaded coolers, and two on board. It was about as heavy as I could get it for normal conditions.
Conditions were very windy and a 1 to 2-foot chop and I took an average over two directions.
Revolution4 19-pitch

RPM MPH GPH MPG
1000 6.00 0.8 7.5

2000 10.10 3.60 2.81

3000 26.60 10.80 2.46

3500 33.00 13.00 2.54

4000 38.15 18.40 2.07

5000 48.80 31.00 1.57

5350 50.25 33.20 1.51
Enertia 21-pitch

RPM MPH GPH MPG
1000 6.10 0.80 7.63

2000 10.00 3.10 3.23

3000 23.00 10.60 2.17

3500 30.50 12.20 2.50

4000 38.50 19.00 2.03

5000 49.00 30.00 1.63

5400 52.75 33.00 1.63
The engines are brand new and I would hope and understand they might give up another 150-RPM or so over the next 50 hours if experience of others is taken into account. As you can see, aside from top end where the Enertias gave me over 2-MPH more, there are no major differences. Both offer maximum cruise of 2.5 MPG at 3,500-RPM, but the Revolution4 propellers do so at a higher speed. This is where most of my boating will be done.
Interestingly enough, whilst both motors pulled the same engine speed with the Enertias, I clearly do not have a matching pair of Revolution4 propellers as one motor drops about 150-RPM.
The real difference came in feel. This can be best described as the difference as between a limo and a sports car, the Enertia propellers being the sports car. The Revolution4 propellers have unbelievable hole shot, taking off really like a rocket, on the plane in a nanosecond, great stern lift, far more than the Enertia propellers in my case, are very smooth definitely hold the plane better and at lower speeds and seem impossible to blow out. The Enertia propellers are more flighty, appear more difficult to match engine speed, are far more sensitive to the throttle, and cannot be trimmed as hard, blowing out quite easily. Work at it and they will reward, go into solid cruise mode and the Revolution4 propellers have it. For top end, however, the Inertia propellers deliver.
In short, I am going back to the Revolutiuon4 propellers. Whilst changing props I did notice that someone on island (Bahamas), thinking they were helpful, had removed the PVS caps, and this may make a slight difference as my dealer said that when he trialled the boat he got a top speed of 51.5 at 5,550-RPM. I now plan to refit them as I assume they make a difference at speed? Anyone had any experience with PVS?
Whilst with the 19's I am revving in the middle of the power band, would I have been better off with the Rev 4 17's? My thinking is that the 19's would give me better economy.
Whilst I am disappointed in top end, I am not in overall feel and power delivery. The added HP has totally altered the character of the boat for the better. Using the car analogy further it has turned a E300 Mercedes into a E63, both being speed limited, but one really handles and accelerates whilst the other just goes. Given some hours on the motors, a less heavily weighted boat, the PVS caps and ideal calm conditions, I would hope to better these figures and end up with a top end with the Revolution4 propellers of around 52/53 MPH. When Mercury bring out the X7 version, that would probably be the ideal combination.
What does this prove? Props are a dark art. It is not only the hull that affects things but the motors as well.
I would be interested to hear any comments on these figures, especially as how I might get any more out of this set up and have a pair of once used Enertia 21-pitch propellers if anyone wants to buy them.
Peter posted 01-01-2007 05:13 PM ET (US)
Based on Yamaha's performance report for the Edgewater 245 with a pair of Yamaha F150s (test weight 5300 lbs) and an assumption that the Yamahas are good for 165 HP as you say, then your boat's predicted top speed with 400 HP should be in the neighborhood of 55 MPH. You are quite close to that now with the Enertias and if your boat weighs more than 5300 lbs, I think your results are right in the expected zone.
The Rev 4s will provide better cruise, better low plane traction and better docking, but will give up top speed as compared to any good quality three blade stainless propeller.
Perry posted 01-01-2007 06:33 PM ET (US)
Good data pinapplepig. I wonder how much more speed the Enertia's would have gotten the twin Yamaha F150's on the Edgewater 245. If the stock Yamaha props on the F150's can push the Edgewater 245 to 50 MPH, maybe 52.75 MPH could have been achieved with Enertias? This makes me wonder why you felt you needed to add 100 more HP to achieve the same top speed with worse fuel economy.
Peter posted 01-01-2007 06:51 PM ET (US)
Perry -- In the test report where 50 MPH was acheived, the F150s were wearing a set of Yamaha's new RELIANCE propellers. According to Yamaha's advertising:
"Yamaha’s new Reliance™ Series propellers provide excellent performance with engines up to 300hp. An all-new blade design delivers more speed at all rpm’s, excellent anti-cavitation, and better grip for added bow lift and top-end speed. Overall handing and turning is significantly enhanced."
I haven't seen any data comparing the performance of these propellers to Enertias. Are you suggesting that these propellers are inferior to Enertias?
Perry posted 01-01-2007 07:26 PM ET (US)
I assumed they used their Saltwater Series propellers.
Is there any doubt that Mercury makes the best propellers on the market today?
jimh posted 01-02-2007 01:10 AM ET (US)
Here are two plots of the data given above. First we look at boat speed as a function of engine speed:
http://continuouswave.com/whaler/reference/graphics/propellerTestGraphs/ ENERTIA_v_REVOLUTION4.png

Next we look at fuel economy as a function of boat speed:
http://continuouswave.com/whaler/reference/graphics/propellerTestGraphs/ ENERTIA_v_REVOLUTION4_MPG.png
pineapplepig posted 01-02-2007 08:54 AM ET (US)
Perry,
Strangely enough, as I would hope you could tell from my post, I was not expecting the top end I have with an extra 70HP as otherwise, as you correctly say, why do it. No one had fitted Etecs to these boats before and for various reasons I wanted Etecs and this was the way to get the most HP onto the transom. I further though I might as well put on 400HP for the small price difference.
However, if you read my post you will note that whilst the top end is similar, I cruise faster still at great economy, sound and look better (!), but most importantly the whole feel of the boat is so totally different. Response throughout the range is electric and these motors have turned the boat into a real sports sedan from a dull old limo. There is more to it than just top end, although I am surprised that I am not getting 55MPH
jimh posted 01-02-2007 08:58 AM ET (US)
Also, I do agree that the Edgewater hull appears to be similar to the classic Boston Whaler hull. It seems to have much of the same general shape. I'd say that the current Edgewater boats have more resemblance to a classic Boston Whaler than the current Boston Whaler boat hulls.
pineapplepig posted 01-02-2007 09:05 AM ET (US)
Jimh
I had the opportunity to look at my EW 245 hull out of the water alongside a classic Outrage 23 circa 1992, and the similarity in the hull design is amazing. It looks like EW have just tweaked a great design as having ridden on a modern 240 when shopping, IMO the older classic hull gave a far softer and better ride. This has since been confirmed by other owners to me.
Peter posted 01-02-2007 09:22 AM ET (US)
Pineapplepig -- I know exactly what you mean by "electric". I took a ride in an Everglades 240 CC powered by a pair of Honda BF150s several months ago. Advancing the throttles to WOT from idle produced a very casual increase in speed. The engine response was best characterized as dull. There was no "leap" out of the water like you get with a 2-stroke when the thottles were advanced. There was little need to tell anybody to hang on when the salesman slammed the throttles down. Not even the much hyped Enertia propeller could save this rig from the experience.
In my opinion, the Everglades 240 CC would benefit from bigger engines in the 4-stroke format. However, its only rated for 300 HP and I suspect that is probably due to transom weight considerations. It certainly is not because of speed because the boat isn't that fast with 300 HP.
jimh posted 01-02-2007 09:26 AM ET (US)
[Re-linked to new graph of MPG as a function of boat speed. Old one had an error in the legend.]
jimh posted 01-02-2007 08:22 PM ET (US)
Looking over the data and the graphs, it looks to me like you've made the right decision: the REVOLUTION4. I don't really see any particular advantage for the ENERTIA, other than the last mile per hour or two in ultimate speed. Ultimate top speed may be an advantage for some boaters, perhaps racers or competitive boaters, but I think most would be willing to forego 2-MPH in the 50-MPH range to get better fuel economy and overall better handling.
The ENERTIA as a propeller design does not seem to excel except in top speed.
The metallurgy of the special alloy used in the ENERTIA ought to applied to the REVOLUTION4 design. This combination would make a really superior propeller. I have tried the REVOLUTION4 myself, and one significant drawback of the propeller is its massive weight. If Mercury can make a Rev4 with the special alloy and cut the weight, they will have a winner on their hands.
pineapplepig posted 01-03-2007 10:59 AM ET (US)
The rev 4 X7 (same material as the Enertia) is apparently due later this year and that is where I am immediately headed.
I am also going to try raising my motors a notch as I can currently trim the Rev 4's beyond the 'up' marker on the trim gauge without them blowing out.
Peter posted 01-03-2007 11:24 AM ET (US)
No matter how good the metallugy may be on the Enertia (we haven't seen any long term durability data yet), the 3-blade Enertia still suffers from a lack of blade surface area as compared to 4-blade propellers. Twin outboard powered V bottom boats seem to benefit overall from the greater surface area that 4-blade propellers provide rather than metallurgical advances in 3-blade propellers.
In twin outboard applications, each of the propellers is located off-center relative to the keel. This causes propeller grip to be more problematic because when the boat rolls about the keel axis from side to side while underway, the height of each of the propellers in the water varies. This does not happen in the case of a single outboard with a propeller on-center with the keel because rolling about the keel axis doesn't change the propeller height in the water for a single outboard. With 3-blade propellers, there is a much higher tendency to have one of the propellers lose grip and "blow out" as the boat rolls from one side to another while underway or in sharp turns where the outside motor is lifted up. The 4-blade propellers provide much better grip due to the greater surface area below the water line and are less easily blown-out.
I have wondered whether the heavy weight of the Rev 4 propeller is actually an advantage rather than a disadvantage in twin outboard applications. To the extent that the grip breaks loose (the propeller becomes unloaded), its rotational speed will not accelerate as quickly as a lighter three-blade propeller like the Enertia and so engine surging caused by an unloaded prop is likely to be somewhat reduced. It will be interesting to compare the performance of a Rev 4-X7 alloy prop with the regular Rev 4.
Given the superior traction of the Rev 4, you may be able to raise your motors up a hole and gain some performance without much loss in the mid-range.
pineapplepig posted 01-05-2007 06:10 PM ET (US)
My Anti Cav plate is currently running at least an inch under water at cruise and also my slip numbers are incrtedibly small, 2% approx, so I am thinking I can raise my motors one or two notches which should get me about 3 mph and even better cruise. I will post my results when, and that is not easy here, I have managed to get the motors raised.
jimh posted 01-06-2007 10:04 AM ET (US)
Peter--That is an excellent point regarding the situation with twin engines and the hull operating with a list in turns. I do not recall that being mentioned before, and I think it is a good observation.
And, again, Peter has made an interesting observation about the weight of the REVOLUTION4 perhaps contributing to the reduced tendency to blow out.
The ENERTIA propeller is something of an amalgam of its material, the new X-7 alloy, and its design, a three-blade propeller apparently intended to produce higher speed performance which has been obtained, in part, from the thinner blade shape made possible by the special alloy.
Regarding the engine mounting height, conventional wisdom says the anti-ventilation (AV) plate ought to be running above the water surface. Raising the motor will reduce the drag. At high speeds the drag of the gear case itself is a significant influence on boat speed. Reducing this drag will likely help with speed, especially in the 50-MPH region.

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Author	Topic: E-TEC, Revolution4 and Enertia Propellers
pineapplepig	posted 01-01-2007 01:53 PM ET (US) Even though my Edgewater 245 is not a Whaler, it is a Dougherty-designed hull and I see it as the same. My experience with my Edgewater may be of interest to Whaler owners when it comes to props. Forgive me, but this is going to be a long post. [Heck--we love long posts, if they are like this one and filled with information--jimh.] Well, finally got the time to try out my new Edgewater 245 which I have hung with twin 200 small bore 2.6-liter E-TEC motors. I was not impressed with the relative lack of performance of the standard Yamaha 150-HP motors the boat comes with from the factory. Also the E-TEC motors really set the boat off with their sharp design. What might be of interest to others in this report is the limited difference in performance with the addition of an extra probably 70-HP--apparently the standard fit Yamaha 150-HP motors put out about 165-HP--but what cannot be really explained here is the difference in hole shot, acceleration, and overall feel, which is truly electric. I have also been evaluating the difference between Mercury REVOLUTION4 and ENERTIA propellers First off, the E-TEC motors: So far I am delighted with them. They are smooth, quiet, very responsive, and when you are pushing them they make a really exceptional turbine-like howl. Fuel economy is great, I think over 2.5-MPG for 12 cylinders is pretty good on a 6,000-lb boat. Oil usage a non-event. Exhaust smell absolutely zero. And for trolling never a hint of exhaust and [fuel burn] under a gallon an hour for the two motors. I do suspect that if you want the full top end that 400-HP would suggest, then you have to go to the 3.3 big block with the torque to run the propellers higher up the range. But then that is just too much weight on the stern. In short, there is no substitute for displacement, but then BRP are squeezing a lot out of a small package. Maximum power is produced at 5,250-RPM and the powerband is 4,650 to 5,850, so according to BRP I am in right zone. Below I post the results as best as I was able to evaluate in less than ideal circumstances and I should say this is my first effort at recording and posting comparative figures. Figures are for both motors. Boat weighed well over 6,000-lbs with full fuel, power assisted steering, full water, full fishing gear, spare anchors, T-Top, loaded coolers, and two on board. It was about as heavy as I could get it for normal conditions. Conditions were very windy and a 1 to 2-foot chop and I took an average over two directions. Revolution4 19-pitch RPM MPH GPH MPG 1000 6.00 0.8 7.5 2000 10.10 3.60 2.81 3000 26.60 10.80 2.46 3500 33.00 13.00 2.54 4000 38.15 18.40 2.07 5000 48.80 31.00 1.57 5350 50.25 33.20 1.51 Enertia 21-pitch RPM MPH GPH MPG 1000 6.10 0.80 7.63 2000 10.00 3.10 3.23 3000 23.00 10.60 2.17 3500 30.50 12.20 2.50 4000 38.50 19.00 2.03 5000 49.00 30.00 1.63 5400 52.75 33.00 1.63 The engines are brand new and I would hope and understand they might give up another 150-RPM or so over the next 50 hours if experience of others is taken into account. As you can see, aside from top end where the Enertias gave me over 2-MPH more, there are no major differences. Both offer maximum cruise of 2.5 MPG at 3,500-RPM, but the Revolution4 propellers do so at a higher speed. This is where most of my boating will be done. Interestingly enough, whilst both motors pulled the same engine speed with the Enertias, I clearly do not have a matching pair of Revolution4 propellers as one motor drops about 150-RPM. The real difference came in feel. This can be best described as the difference as between a limo and a sports car, the Enertia propellers being the sports car. The Revolution4 propellers have unbelievable hole shot, taking off really like a rocket, on the plane in a nanosecond, great stern lift, far more than the Enertia propellers in my case, are very smooth definitely hold the plane better and at lower speeds and seem impossible to blow out. The Enertia propellers are more flighty, appear more difficult to match engine speed, are far more sensitive to the throttle, and cannot be trimmed as hard, blowing out quite easily. Work at it and they will reward, go into solid cruise mode and the Revolution4 propellers have it. For top end, however, the Inertia propellers deliver. In short, I am going back to the Revolutiuon4 propellers. Whilst changing props I did notice that someone on island (Bahamas), thinking they were helpful, had removed the PVS caps, and this may make a slight difference as my dealer said that when he trialled the boat he got a top speed of 51.5 at 5,550-RPM. I now plan to refit them as I assume they make a difference at speed? Anyone had any experience with PVS? Whilst with the 19's I am revving in the middle of the power band, would I have been better off with the Rev 4 17's? My thinking is that the 19's would give me better economy. Whilst I am disappointed in top end, I am not in overall feel and power delivery. The added HP has totally altered the character of the boat for the better. Using the car analogy further it has turned a E300 Mercedes into a E63, both being speed limited, but one really handles and accelerates whilst the other just goes. Given some hours on the motors, a less heavily weighted boat, the PVS caps and ideal calm conditions, I would hope to better these figures and end up with a top end with the Revolution4 propellers of around 52/53 MPH. When Mercury bring out the X7 version, that would probably be the ideal combination. What does this prove? Props are a dark art. It is not only the hull that affects things but the motors as well. I would be interested to hear any comments on these figures, especially as how I might get any more out of this set up and have a pair of once used Enertia 21-pitch propellers if anyone wants to buy them.
Peter	posted 01-01-2007 05:13 PM ET (US) Based on Yamaha's performance report for the Edgewater 245 with a pair of Yamaha F150s (test weight 5300 lbs) and an assumption that the Yamahas are good for 165 HP as you say, then your boat's predicted top speed with 400 HP should be in the neighborhood of 55 MPH. You are quite close to that now with the Enertias and if your boat weighs more than 5300 lbs, I think your results are right in the expected zone. The Rev 4s will provide better cruise, better low plane traction and better docking, but will give up top speed as compared to any good quality three blade stainless propeller.
Perry	posted 01-01-2007 06:33 PM ET (US) Good data pinapplepig. I wonder how much more speed the Enertia's would have gotten the twin Yamaha F150's on the Edgewater 245. If the stock Yamaha props on the F150's can push the Edgewater 245 to 50 MPH, maybe 52.75 MPH could have been achieved with Enertias? This makes me wonder why you felt you needed to add 100 more HP to achieve the same top speed with worse fuel economy.
Peter	posted 01-01-2007 06:51 PM ET (US) Perry -- In the test report where 50 MPH was acheived, the F150s were wearing a set of Yamaha's new RELIANCE propellers. According to Yamaha's advertising: "Yamaha’s new Reliance™ Series propellers provide excellent performance with engines up to 300hp. An all-new blade design delivers more speed at all rpm’s, excellent anti-cavitation, and better grip for added bow lift and top-end speed. Overall handing and turning is significantly enhanced." I haven't seen any data comparing the performance of these propellers to Enertias. Are you suggesting that these propellers are inferior to Enertias?
Perry	posted 01-01-2007 07:26 PM ET (US) I assumed they used their Saltwater Series propellers. Is there any doubt that Mercury makes the best propellers on the market today?
jimh	posted 01-02-2007 01:10 AM ET (US) Here are two plots of the data given above. First we look at boat speed as a function of engine speed: http://continuouswave.com/whaler/reference/graphics/propellerTestGraphs/ ENERTIA_v_REVOLUTION4.png Next we look at fuel economy as a function of boat speed: http://continuouswave.com/whaler/reference/graphics/propellerTestGraphs/ ENERTIA_v_REVOLUTION4_MPG.png
pineapplepig	posted 01-02-2007 08:54 AM ET (US) Perry, Strangely enough, as I would hope you could tell from my post, I was not expecting the top end I have with an extra 70HP as otherwise, as you correctly say, why do it. No one had fitted Etecs to these boats before and for various reasons I wanted Etecs and this was the way to get the most HP onto the transom. I further though I might as well put on 400HP for the small price difference. However, if you read my post you will note that whilst the top end is similar, I cruise faster still at great economy, sound and look better (!), but most importantly the whole feel of the boat is so totally different. Response throughout the range is electric and these motors have turned the boat into a real sports sedan from a dull old limo. There is more to it than just top end, although I am surprised that I am not getting 55MPH
jimh	posted 01-02-2007 08:58 AM ET (US) Also, I do agree that the Edgewater hull appears to be similar to the classic Boston Whaler hull. It seems to have much of the same general shape. I'd say that the current Edgewater boats have more resemblance to a classic Boston Whaler than the current Boston Whaler boat hulls.
pineapplepig	posted 01-02-2007 09:05 AM ET (US) Jimh I had the opportunity to look at my EW 245 hull out of the water alongside a classic Outrage 23 circa 1992, and the similarity in the hull design is amazing. It looks like EW have just tweaked a great design as having ridden on a modern 240 when shopping, IMO the older classic hull gave a far softer and better ride. This has since been confirmed by other owners to me.
Peter	posted 01-02-2007 09:22 AM ET (US) Pineapplepig -- I know exactly what you mean by "electric". I took a ride in an Everglades 240 CC powered by a pair of Honda BF150s several months ago. Advancing the throttles to WOT from idle produced a very casual increase in speed. The engine response was best characterized as dull. There was no "leap" out of the water like you get with a 2-stroke when the thottles were advanced. There was little need to tell anybody to hang on when the salesman slammed the throttles down. Not even the much hyped Enertia propeller could save this rig from the experience. In my opinion, the Everglades 240 CC would benefit from bigger engines in the 4-stroke format. However, its only rated for 300 HP and I suspect that is probably due to transom weight considerations. It certainly is not because of speed because the boat isn't that fast with 300 HP.
jimh	posted 01-02-2007 09:26 AM ET (US) [Re-linked to new graph of MPG as a function of boat speed. Old one had an error in the legend.]
jimh	posted 01-02-2007 08:22 PM ET (US) Looking over the data and the graphs, it looks to me like you've made the right decision: the REVOLUTION4. I don't really see any particular advantage for the ENERTIA, other than the last mile per hour or two in ultimate speed. Ultimate top speed may be an advantage for some boaters, perhaps racers or competitive boaters, but I think most would be willing to forego 2-MPH in the 50-MPH range to get better fuel economy and overall better handling. The ENERTIA as a propeller design does not seem to excel except in top speed. The metallurgy of the special alloy used in the ENERTIA ought to applied to the REVOLUTION4 design. This combination would make a really superior propeller. I have tried the REVOLUTION4 myself, and one significant drawback of the propeller is its massive weight. If Mercury can make a Rev4 with the special alloy and cut the weight, they will have a winner on their hands.
pineapplepig	posted 01-03-2007 10:59 AM ET (US) The rev 4 X7 (same material as the Enertia) is apparently due later this year and that is where I am immediately headed. I am also going to try raising my motors a notch as I can currently trim the Rev 4's beyond the 'up' marker on the trim gauge without them blowing out.
Peter	posted 01-03-2007 11:24 AM ET (US) No matter how good the metallugy may be on the Enertia (we haven't seen any long term durability data yet), the 3-blade Enertia still suffers from a lack of blade surface area as compared to 4-blade propellers. Twin outboard powered V bottom boats seem to benefit overall from the greater surface area that 4-blade propellers provide rather than metallurgical advances in 3-blade propellers. In twin outboard applications, each of the propellers is located off-center relative to the keel. This causes propeller grip to be more problematic because when the boat rolls about the keel axis from side to side while underway, the height of each of the propellers in the water varies. This does not happen in the case of a single outboard with a propeller on-center with the keel because rolling about the keel axis doesn't change the propeller height in the water for a single outboard. With 3-blade propellers, there is a much higher tendency to have one of the propellers lose grip and "blow out" as the boat rolls from one side to another while underway or in sharp turns where the outside motor is lifted up. The 4-blade propellers provide much better grip due to the greater surface area below the water line and are less easily blown-out. I have wondered whether the heavy weight of the Rev 4 propeller is actually an advantage rather than a disadvantage in twin outboard applications. To the extent that the grip breaks loose (the propeller becomes unloaded), its rotational speed will not accelerate as quickly as a lighter three-blade propeller like the Enertia and so engine surging caused by an unloaded prop is likely to be somewhat reduced. It will be interesting to compare the performance of a Rev 4-X7 alloy prop with the regular Rev 4. Given the superior traction of the Rev 4, you may be able to raise your motors up a hole and gain some performance without much loss in the mid-range.
pineapplepig	posted 01-05-2007 06:10 PM ET (US) My Anti Cav plate is currently running at least an inch under water at cruise and also my slip numbers are incrtedibly small, 2% approx, so I am thinking I can raise my motors one or two notches which should get me about 3 mph and even better cruise. I will post my results when, and that is not easy here, I have managed to get the motors raised.
jimh	posted 01-06-2007 10:04 AM ET (US) Peter--That is an excellent point regarding the situation with twin engines and the hull operating with a list in turns. I do not recall that being mentioned before, and I think it is a good observation. And, again, Peter has made an interesting observation about the weight of the REVOLUTION4 perhaps contributing to the reduced tendency to blow out. The ENERTIA propeller is something of an amalgam of its material, the new X-7 alloy, and its design, a three-blade propeller apparently intended to produce higher speed performance which has been obtained, in part, from the thinner blade shape made possible by the special alloy. Regarding the engine mounting height, conventional wisdom says the anti-ventilation (AV) plate ought to be running above the water surface. Raising the motor will reduce the drag. At high speeds the drag of the gear case itself is a significant influence on boat speed. Reducing this drag will likely help with speed, especially in the 50-MPH region.