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Author Topic:   CONTINUOUSWAVE Sets New Speed Record

jimh posted 10-17-2006 12:24 AM ET (US)
This weekend we had CONTINUOUSWAVE out for a final run before putting the boat away for the season. The hull was stripped of everything non-essential. All the canvas, cushions, extra gear, etc, were removed. The fuel tank was down to 1/4-FULL on the gauge. As a result the total boat weight was very light in comparison to our usual situation when cruising.
In addition, the air and water temperatures were both in the low 50-degree-F range. We also had a tail wind of about 15-MPH.
All of these factors added up to a new speed record: 42.5-MPH at 5,900-RPM with a 17-inch pitch propeller. I mention this for a couple of reasons:
--this speed is about 5-MPH faster than the usual top speed we see when the boat is loaded down with gear, the canvas is up, and the air and water temperatures are both much warmer;
--the engine is the same engine with the same power as when the boat has been tested in the past and run much slower.
I think that this much variation is entirely reasonable. I've seen it with my own eyes. There is nothing magical going on with the engine. The explanations are simple:
--the boat is lighter so it goes faster;
--the air is colder so it is denser. The engine draws more in than when it is warmer, and this helps the engine run better;
--the water is colder so it is denser. The propeller operates slightly more efficiently.
All of these factors are favorable to more speed. They add up to a rather substantial increase in speed. And this is on a test with the same boat and the same motor!
There could be a bit of variation in the engine, as I have tweaked it up a bit, but, in the main, I don't think it is running substantially better than it was when I was only getting 37.5-MPH when loaded with cruising gear and canvas. The cold air was to its liking.
Even more interesting, I think this new top speed is about 7-MPH faster than the boat would go when I first bought it. Back then it was laboring with the wrong propeller. It makes me wonder: would the seller have sold it if it was cranking 42.5-MPH for him?
And I am not done, yet. These results still show 16-percent propeller slip, so I believe there might be another 1-MPH still available. It was too cold to swap propellers, but I think I might have been able to get a bit more top speed out of her with a different prop.
OK--What's my point? My results show how much variation in speed can be seen in testing. Remember, it is the same boat and the same motor, and the top speed is all over the map, from as low as 36-MPH to as high as 42.5-MPH. When performance reports are made, it is wise to keep in mind that they are subject to variations. I don't look at any of them as gospel--just guidelines. I may never see 42.5-MPH on that boat again.
jimh posted 10-17-2006 12:27 AM ET (US)
Also, I forgot to mention, the boat set a new record for fuel economy. We saw fuel economy of 2.5-MPG at cruise, a figure we never approached before! That cold air can do wonders for engine performance.
highanddry posted 10-17-2006 04:31 AM ET (US)
Well, yeah, and that is what I said in numerous posts when I dissagreed with the constantly and continuous quoting of Boston Whaler's performance specifications for various boats. There results are hardly all encompasing and thus it is quite possible a particular boat/engine can perform slower or faster than their specs. My Nantucket routinely runs closer to 50 than 40 wide open (two GPS in agreement), trimmed out, zero wind, two way run, cool day, moderate to light load, half or less fuel, all canvas stowed down but Boston Whaler says 44 MPH. Engines generally produce more power on cool and dry days at sealevel pressure. No mystery there. On calm water with just a bit of ripple to it our Nantucket will get up on top and haul butt, just about 50 MPH. Your results don't surprise me a bit.
elaelap posted 10-17-2006 08:56 AM ET (US)
Geeezzz, jimh, and you a sailor. Let's see: 42.5 mph minus 15 mph for the lift from that following wind makes, uh, uh, about 27+ mph true, not so very impressive if you ask me...(I'd put one of those nasty smiley emoticrons or whatever ya call 'em right here, but I know you hate 'em and I know you'll get the joke, even though some other folks at this website seem to lack a little understanding of irony).
Not an entirely bad way to end the season, old bud. Thanks again for this wonderful website, Jim.
Tony
You know, sorry, I was just rethinking this post and realized that you probably made the run in two directions--upwind and downwind--and then averaged the two runs. Hmmm, by my calculations that means that the run into that 15 mph breeze was actually made at 57.5 mph...not bad at all; not too bad at all.
jimh posted 10-17-2006 09:50 AM ET (US)
Tony--the next step is to take CONTINUOUSWAVE to the northern Pacific. There I will get the benefit of saltwater (denser) and both colder water and air. I may be able to get a few more miles per hour from the boat. And, even better, I will be down at sea level, so even more engine horsepower.
Seriously, all of these factors add up to differences in results. Right here we have much more variation in speed than could ever be attributed to an intentional shading of the horsepower rating by a manufacturer under the stricter measurements now used in emission testing of modern engines. That notion is often proposed to account for such speed differences in anecdotal reports of performance. I think there is a much more plausible explanation: the test conditions.
BQUICK posted 10-17-2006 12:37 PM ET (US)
Barometric pressure make a big difference, too.
jimh posted 10-17-2006 01:48 PM ET (US)
Well now, actually, if you give this some more thought, on these modern engines there are some sensors which may compensate for some of these factors, at least as far as the engine performance is concerned. A modern engine can monitor air temperature and barometric pressure, and it will make some adjustments for them. Exactly how well it compensates is up to the skill of the designer of the engine, but it is possible for these factors to be considered in the engine's fuel and ignition systems. A modern engine may not be affected as much as my classic old carburetor motor seems to be by such things.
However, the engine cannot affect other devices, such as the hull itself and the propeller. Colder, denser water will perhaps influence how they perform. There may be, for example, less tendency for cavitation in very cold water, and this factor will influence results no matter how the engine is compensated for temperature. The hull will have slightly less draft in colder, denser water. These little differences may add up to a measureable difference in top speed.
Another influence is sea state. On my record setting run we had just a tiny bit of chop, a few inches of wave action. This is often mentioned as being the optimum situation for speed, preferable even to a glassy calm, as it puts more air under the hull and breaks up any surface friction.
The Judge posted 10-17-2006 01:51 PM ET (US)
Slight chop and being sea level on salt water is your best bet like you stated. My 70 Suzuki EFI would pick up about 1mph in winter, not much but it was about 100-150rpms. I will post this winter if my 115 makes any difference in colder weather as well.
bsmotril posted 10-17-2006 02:09 PM ET (US)
Everthing gets a bit more "pep in their step" when fall hits, even outboard motors.
BillS
Binkie posted 10-17-2006 02:14 PM ET (US)
This is very unusual. For years, back in the day, outboard speed records were set at Salton Sea in California, which was a salt water lake with very high salt content. The records were always set in the summer at daybreak, when the humidity was very high, It is well known with the speed people that dense humid air makes more power.
Rich
highanddry posted 10-17-2006 02:32 PM ET (US)
Dense, yes, humid no, fuel needs O2 to burn, not water vapor. However, warter injection is an old trick to squeeze power such as on some old radials I have worked on that use water injection. The water vaporises as injected into the manifold causing cooling (latency effect) and also acts to prevent detonation.
Computers can control mixture and spark etc but thye cannot make the air denser, cool and therefore dense air will make more power all else equal.
Sal DiMercurio posted 10-17-2006 04:40 PM ET (US)
Jin H., glad to see you mention you also got your best fuel economy at 2.5 mpg.
When I read about people getting 3 - 4 mpg on a 6 cylinder carbed pre 1997 engine on 20'+ boats, I often wonder how they come up with these numbers, as I've never ever seen a "V"6 carbed pre 1997 engine get better than 2.5 mpg. at cruise of approx 4000 - 4200 rpms.
My cruise rpm on my old 1991 - 150 hp 2 stroke on a very light hull [ 1979 V 20 Outrage....1500 lbs dry ] was 3500 - 3700 rpms & 2 mpg was all she wrote.
Yes, that cold dense air will do wonders for the way the engine runs,...almost as good as washing the car tune up.
Ever notice how much pep your car or truck has when it rains,...yep, they also like moisture.
Sal
BQUICK posted 10-19-2006 02:20 PM ET (US)
Sal said: "Ever notice how much pep your car or truck has when it rains,...yep, they also like moisture."

Probably due to increased timing from computer/knock sensor.
Usually when it rains the barometer is low and power reduced.
My drag car (700 hp) easily picks up 30 hp from cool, 30.50 barometer vs. hot, 29.70 barometer.
Bella con23 posted 10-19-2006 09:57 PM ET (US)
jimh - Get a rev. 4 on that thing and try again!

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Author	Topic: CONTINUOUSWAVE Sets New Speed Record
jimh	posted 10-17-2006 12:24 AM ET (US) This weekend we had CONTINUOUSWAVE out for a final run before putting the boat away for the season. The hull was stripped of everything non-essential. All the canvas, cushions, extra gear, etc, were removed. The fuel tank was down to 1/4-FULL on the gauge. As a result the total boat weight was very light in comparison to our usual situation when cruising. In addition, the air and water temperatures were both in the low 50-degree-F range. We also had a tail wind of about 15-MPH. All of these factors added up to a new speed record: 42.5-MPH at 5,900-RPM with a 17-inch pitch propeller. I mention this for a couple of reasons: --this speed is about 5-MPH faster than the usual top speed we see when the boat is loaded down with gear, the canvas is up, and the air and water temperatures are both much warmer; --the engine is the same engine with the same power as when the boat has been tested in the past and run much slower. I think that this much variation is entirely reasonable. I've seen it with my own eyes. There is nothing magical going on with the engine. The explanations are simple: --the boat is lighter so it goes faster; --the air is colder so it is denser. The engine draws more in than when it is warmer, and this helps the engine run better; --the water is colder so it is denser. The propeller operates slightly more efficiently. All of these factors are favorable to more speed. They add up to a rather substantial increase in speed. And this is on a test with the same boat and the same motor! There could be a bit of variation in the engine, as I have tweaked it up a bit, but, in the main, I don't think it is running substantially better than it was when I was only getting 37.5-MPH when loaded with cruising gear and canvas. The cold air was to its liking. Even more interesting, I think this new top speed is about 7-MPH faster than the boat would go when I first bought it. Back then it was laboring with the wrong propeller. It makes me wonder: would the seller have sold it if it was cranking 42.5-MPH for him? And I am not done, yet. These results still show 16-percent propeller slip, so I believe there might be another 1-MPH still available. It was too cold to swap propellers, but I think I might have been able to get a bit more top speed out of her with a different prop. OK--What's my point? My results show how much variation in speed can be seen in testing. Remember, it is the same boat and the same motor, and the top speed is all over the map, from as low as 36-MPH to as high as 42.5-MPH. When performance reports are made, it is wise to keep in mind that they are subject to variations. I don't look at any of them as gospel--just guidelines. I may never see 42.5-MPH on that boat again.
jimh	posted 10-17-2006 12:27 AM ET (US) Also, I forgot to mention, the boat set a new record for fuel economy. We saw fuel economy of 2.5-MPG at cruise, a figure we never approached before! That cold air can do wonders for engine performance.
highanddry	posted 10-17-2006 04:31 AM ET (US) Well, yeah, and that is what I said in numerous posts when I dissagreed with the constantly and continuous quoting of Boston Whaler's performance specifications for various boats. There results are hardly all encompasing and thus it is quite possible a particular boat/engine can perform slower or faster than their specs. My Nantucket routinely runs closer to 50 than 40 wide open (two GPS in agreement), trimmed out, zero wind, two way run, cool day, moderate to light load, half or less fuel, all canvas stowed down but Boston Whaler says 44 MPH. Engines generally produce more power on cool and dry days at sealevel pressure. No mystery there. On calm water with just a bit of ripple to it our Nantucket will get up on top and haul butt, just about 50 MPH. Your results don't surprise me a bit.
elaelap	posted 10-17-2006 08:56 AM ET (US) Geeezzz, jimh, and you a sailor. Let's see: 42.5 mph minus 15 mph for the lift from that following wind makes, uh, uh, about 27+ mph true, not so very impressive if you ask me...(I'd put one of those nasty smiley emoticrons or whatever ya call 'em right here, but I know you hate 'em and I know you'll get the joke, even though some other folks at this website seem to lack a little understanding of irony). Not an entirely bad way to end the season, old bud. Thanks again for this wonderful website, Jim. Tony You know, sorry, I was just rethinking this post and realized that you probably made the run in two directions--upwind and downwind--and then averaged the two runs. Hmmm, by my calculations that means that the run into that 15 mph breeze was actually made at 57.5 mph...not bad at all; not too bad at all.
jimh	posted 10-17-2006 09:50 AM ET (US) Tony--the next step is to take CONTINUOUSWAVE to the northern Pacific. There I will get the benefit of saltwater (denser) and both colder water and air. I may be able to get a few more miles per hour from the boat. And, even better, I will be down at sea level, so even more engine horsepower. Seriously, all of these factors add up to differences in results. Right here we have much more variation in speed than could ever be attributed to an intentional shading of the horsepower rating by a manufacturer under the stricter measurements now used in emission testing of modern engines. That notion is often proposed to account for such speed differences in anecdotal reports of performance. I think there is a much more plausible explanation: the test conditions.
BQUICK	posted 10-17-2006 12:37 PM ET (US) Barometric pressure make a big difference, too.
jimh	posted 10-17-2006 01:48 PM ET (US) Well now, actually, if you give this some more thought, on these modern engines there are some sensors which may compensate for some of these factors, at least as far as the engine performance is concerned. A modern engine can monitor air temperature and barometric pressure, and it will make some adjustments for them. Exactly how well it compensates is up to the skill of the designer of the engine, but it is possible for these factors to be considered in the engine's fuel and ignition systems. A modern engine may not be affected as much as my classic old carburetor motor seems to be by such things. However, the engine cannot affect other devices, such as the hull itself and the propeller. Colder, denser water will perhaps influence how they perform. There may be, for example, less tendency for cavitation in very cold water, and this factor will influence results no matter how the engine is compensated for temperature. The hull will have slightly less draft in colder, denser water. These little differences may add up to a measureable difference in top speed. Another influence is sea state. On my record setting run we had just a tiny bit of chop, a few inches of wave action. This is often mentioned as being the optimum situation for speed, preferable even to a glassy calm, as it puts more air under the hull and breaks up any surface friction.
The Judge	posted 10-17-2006 01:51 PM ET (US) Slight chop and being sea level on salt water is your best bet like you stated. My 70 Suzuki EFI would pick up about 1mph in winter, not much but it was about 100-150rpms. I will post this winter if my 115 makes any difference in colder weather as well.
bsmotril	posted 10-17-2006 02:09 PM ET (US) Everthing gets a bit more "pep in their step" when fall hits, even outboard motors. BillS
Binkie	posted 10-17-2006 02:14 PM ET (US) This is very unusual. For years, back in the day, outboard speed records were set at Salton Sea in California, which was a salt water lake with very high salt content. The records were always set in the summer at daybreak, when the humidity was very high, It is well known with the speed people that dense humid air makes more power. Rich
highanddry	posted 10-17-2006 02:32 PM ET (US) Dense, yes, humid no, fuel needs O2 to burn, not water vapor. However, warter injection is an old trick to squeeze power such as on some old radials I have worked on that use water injection. The water vaporises as injected into the manifold causing cooling (latency effect) and also acts to prevent detonation. Computers can control mixture and spark etc but thye cannot make the air denser, cool and therefore dense air will make more power all else equal.
Sal DiMercurio	posted 10-17-2006 04:40 PM ET (US) Jin H., glad to see you mention you also got your best fuel economy at 2.5 mpg. When I read about people getting 3 - 4 mpg on a 6 cylinder carbed pre 1997 engine on 20'+ boats, I often wonder how they come up with these numbers, as I've never ever seen a "V"6 carbed pre 1997 engine get better than 2.5 mpg. at cruise of approx 4000 - 4200 rpms. My cruise rpm on my old 1991 - 150 hp 2 stroke on a very light hull [ 1979 V 20 Outrage....1500 lbs dry ] was 3500 - 3700 rpms & 2 mpg was all she wrote. Yes, that cold dense air will do wonders for the way the engine runs,...almost as good as washing the car tune up. Ever notice how much pep your car or truck has when it rains,...yep, they also like moisture. Sal
BQUICK	posted 10-19-2006 02:20 PM ET (US) Sal said: "Ever notice how much pep your car or truck has when it rains,...yep, they also like moisture." Probably due to increased timing from computer/knock sensor. Usually when it rains the barometer is low and power reduced. My drag car (700 hp) easily picks up 30 hp from cool, 30.50 barometer vs. hot, 29.70 barometer.
Bella con23	posted 10-19-2006 09:57 PM ET (US) jimh - Get a rev. 4 on that thing and try again!