Slow water?
Printed From: CorrectCraftFan.com
Category: General Correct Craft Discussion
Forum Name: General Discussion
Forum Discription: Anything Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=48147
Printed Date: April-27-2024 at 6:56am
Topic: Slow water?
Posted By: GottaSki
Subject: Slow water?
Date Posted: October-15-2019 at 10:39am
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Anybody else experience a maxspeed drop late in season after the water chills out? Hadn't used the boat wot in 3-4 weeks, and the water temp dropped a bunch since. I know the water feels 'harder' to the ski when cold. maybe a 4-blade thrashing more-dense water has even more parasitic drag than usual? Its down a solid 3mph and only 4700rpm ( finally on a working tach) vs what sounded like a solid 5k prior, The stern failed to 'lift' and get it to 46-47 mph. Seems i remember drops in performance late in season, but likely faster one goes, the bigger the delta? I suspect its more drag.than what late-season bottom growth could do, as its been there all season and it got a good wipe down about 5 weeks ago. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Replies:
Posted By: Hollywood
Date Posted: October-15-2019 at 12:27pm
| I seem to recall my boat running faster in the cold. |
Posted By: RealDeez
Date Posted: October-15-2019 at 12:38pm
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This sounds like an opportunity for research. It might be hard to rule out performance changes in the motor/trans over the course of a season though. This year was not good for me regarding access to the boat but next year I could probably do a beginning/middle/end of season WOT run and see... temps would range from 50-80 in the water over the course of the season depending on when we drop it in/pull it out and weather... Could the temperature of the water coming in the cooling system be part of that? I'm not an engine guy very much but I imagine if the water coming in is cold it may affect combustion some when the thermostat opens... Cold air in the intake may make a difference too but I guess that would probably be an improvement. A little cursory research says the water temp will matter very little to the speed. Air temp/humidity may affect it but if anything, colder temps should be faster by that analysis. Most external accounts seem to imply you should be faster not slower... unless the oil, is thicker because of the cooler temps and cooling water moving through the trans, for example. Just spitballing phrenetically... so don't mind me. ------------- Lake James, IN 93 Sport Nautique |
Posted By: gt40KS
Date Posted: October-15-2019 at 2:03pm
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Hydro resistance issue aside, engines will run better or worse depending on temp and humidity. Generally colder, dryer air will increase performance because of the denser air charge. Thus most would likely experience a perceivable increase in performance after a marked drop in temperature. That being said, if the norm is a 10-15% relative humidity and it jumps to 80-90% you won't see that increase, and possibly even a decrease, even if the temps are lower. But honestly, the kind of temp difference that make performance physically noticeable is probably much greater than what you've experienced thus far anyway. Further, there are studies showing the correlation between charge air temperatures and performance. It was suggested (and some say proven) that the key is really the DIFFERENCE in cylinder temperature and charge temperature that determines the relative boost you may have in relation to temperature changes. As such if the engine is up to running temps but the cooling system is helping to provide a cooler cylinder temperature as well as cooler external air temps (less excessive humidity) a marked increase in combustion rate would follow. I'm thinking if you are feeling a decrease in performance it's either due to a much higher humidity than you normally experience or there is another issue causing it. I can't speak to the hydro-dynamics here ... perhaps there's a hydro engineer in the forum? ------------- JCCI 1995 Ski Nautique GT40 |
Posted By: TRBenj
Date Posted: October-15-2019 at 2:15pm
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A significant drop in engine rpm would be unexpected, especially when considering the cooler air temps. Might give everything a once over under the box? While I would expect WOT rpm to be largely consistent, the resulting speed can be influenced by a number of things and can vary a little even day to day based on ambient/water conditions (including temp, humidity, etc) and boat load (# of passengers and location, fuel quantity, etc). Since yours are tracking together, I’d investigate. |
Posted By: GottaSki
Date Posted: October-15-2019 at 2:23pm
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huh. Air temps were summery yesterday afternoon , nothing that would alter the underhood temperature. Engine temp normal 165, thermostatically controlled Little more fuel than usual and a cold water, thats about it ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: GottaSki
Date Posted: October-15-2019 at 2:29pm
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SCIENCE! she blinded me... alright, i was looking at water density stuff, and came across this,... more intriguing than density, is water viscosity vs temp If i read this right, plot suggests that water temp dropping from 23C to 16C (75 to 62F) results an increase in viscosity about 15% With 4 blades thrashing (and the oj is a thrasher) i think this explains it ok, engine isn't sick.  ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: TRBenj
Date Posted: October-15-2019 at 4:57pm
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Wishful thinking, perhaps? How many data points do you have to characterize the engine/boats performance? If minimal, do you have reason to believe that the previous points were achieved in optimal conditions (or borderline unbelievable)? 300rpm is a lot of RPM to lose- I can’t say I’ve ever seen that much variation due to conditions. 3mph, yes. All bodies of water act a little different but more often than not my boats run faster when it’s cooler out. |
Posted By: MrMcD
Date Posted: October-15-2019 at 7:22pm
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Cool air does aid making power. If that cool air has a lot of moisture, say it is a foggy day it will rob power as the moisture displaces fuel/air so you get a little less power. At least that is what the Drag Racers tell me. We were at Sonoma NHRA race and it can be 100 degrees and dry air or 60 and foggy air on the same weekend. I thought the fog would make them run hard but it robbed power. The fog came in and the Racers were all upset. ------------- |
Posted By: KENO
Date Posted: October-15-2019 at 8:09pm
Slow water.............here's slow water But anyways, after reading Tom's story I decided to take a boat ride today and see what my results would be. Kinda like Tom's conditions air temp was probably mid sixties and the water had cooled off from a max of about 82 in late summer to 56 today. We'll call the boat "old scuzzy bottom". it was cleaned about a month ago and scuzzed up a bit since then Knowing what it has for a top speed, I checked it again today (and a lot of other days under various conditions) and it was basically the same as when the water was in the 80's. with about the same amount of scuzziness on the bottom. It lives in the water for 5 to 6 months of the year with a bottom cleaning every now and then So Tom, I think there's something "not right" with the boat/engine 3 mph and a few hundred RPM loss sounds a lot like secondaries that aren't opening just as a first guess  Just think how much of a dog it would be in 40 degree water if the viscosity had that much of an effect |
Posted By: Gary S
Date Posted: October-15-2019 at 9:22pm
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Don't be getting gundriver all excited- he'll be cutting off the top off his boat and mounting it on his sled ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: GottaSki
Date Posted: October-15-2019 at 9:31pm
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Your right men, sketchy data! But I can't let gp its not the first time I've noticed drop in top speed this time of year, my 41 mph boat would turn into 39 when I take it out for the year, then turns back into 41 mph the next season, no mods. Maybe the calculus says just get the 541. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: JoeinNY
Date Posted: October-16-2019 at 6:43pm
Sketchy data indeed as this would be the first time with a working tach? so 300 rpm drop cannot be confirmed. However, In my experience a 300 rpm drop would be rarely caused by serious engine troubles - more along the line of not getting full advance or even a carb issue dumping in extra gas. Although being a newish install two things that are nice to rule out would be a cam lobe wearing down due to break in not working out, or a distributor gear wearing quickly and that causing noticeable changes in timing. Catching either of those early would be better than waiting. Also any chance a new setup has melted an ignition wire a bit would be worth a look see as well... Whenever I have a bunch of time and money invested and any little noise, stumble, or miss occurs it helps my sanity if I start with a compression test so I can rule out anything super horrible and get back on a logical footing. Edit - also once chased a boat that was slow and ran like crap in the cold where it was the voltage drop from the heater/seat heaters that was the culprit... ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
GottaSki wrote:Posted By: stepper459
Date Posted: October-18-2019 at 1:21pm
Man, I want to know more about that pic. |
Posted By: MrMcD
Date Posted: October-18-2019 at 2:05pm
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Me Too, I be thinking someone thought they could wait one more weekend to pull the boat out and messed up. Makes for a great photo though! I like it. Do you suppose they winterized the engine? A Nautique owner would know better! Mark  ------------- |
Posted By: 8122pbrainard
Date Posted: October-18-2019 at 2:27pm
Well, they sawed a hole in the ice the size of the hull. Brought the boat out on the ice on the trailer. Slid the boat off the trailer into the open water and then paced some loose snow in around the gaps between the hull and the ice. All for the photo shoot.  ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: stepper459
Date Posted: October-18-2019 at 3:02pm
That's what I'm guessing. I know when the lake freezes over on a cold stretch, you can go from open water to 2+ inches of ice in a few days. An inch is surprisingly strong; we pulled our dock last year with an inch of ice and we stood on the ice to carry the dock to shore - mind you, it's only knee deep by then so if we fell in, no big deal. |
Posted By: Gary S
Date Posted: October-18-2019 at 4:34pm
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Have to be pretty board to actually go out cut a hole and launch the boat into it. Hold my beer and watch this. I like parking in the shade and looking at ice in my glass ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: 8122pbrainard
Date Posted: October-18-2019 at 4:40pm
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Gary, In the dead of winter up here, people do some weird things to keep themselves busy!  ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: KENO
Date Posted: October-18-2019 at 4:43pm
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Here'as a link to what may or may not be the real or semi real story back in 2005 http://www.tigeowners.com/forum/showthread.php?1703-Tig%E9-rescue" rel="nofollow - link |
Posted By: MrMcD
Date Posted: October-18-2019 at 9:46pm
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That was a good read Keno, your search skills are almost mystic! ------------- |
Posted By: Gary S
Date Posted: October-18-2019 at 10:05pm
I like that Pete,is that a recent photo ? - American ingenuity at it's finest,one registration, all year use ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: KENO
Date Posted: October-18-2019 at 11:05pm
Nothing mystic at all. I let Google do all the work, just right click on the picture and a little menu comes up, then go to the line that says "search Google for image" and click on that and in a few seconds you have results and as you scroll down the page you see the places where it was posted Doesn't have that search feature for all pictures for whatever reason That's about as technical as I can get I think an 10 year old showed me how to do it originally |
Posted By: gun-driver
Date Posted: October-19-2019 at 12:26am
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https://www.youtube.com/watch?v=7_F0fy1XyoE" rel="nofollow - https://www.youtube.com/watch?v=7_F0fy1XyoE Best of both worlds 
|
Posted By: MrMcD
Date Posted: October-19-2019 at 5:06am
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Dan Mac Computers don't offer a right click, I am PC trained and trying to learn how to use a Mac. Simple things are hidden in the Mac, I have a lot to learn. Pete, is that your winter row boat! Creative, in the summer you can use it as a stump grinder to keep it busy year round! ------------- |
Posted By: Mpost
Date Posted: October-19-2019 at 10:34am
 ------------- 84 SN Sold 98 SN Lund Pro V 1975 Alumacraft |
Posted By: DHMcFadin
Date Posted: October-19-2019 at 1:06pm
To right click on a Mac you click with two fingers at once on the track pad or you can press control+click to right click. ------------- 1999 Longhorn Nautique 1995 Nautique Super Sport https://www.instagram.com/longhorn_nautique/" rel="nofollow - https://www.instagram.com/longhorn_nautique/ |
Posted By: MrMcD
Date Posted: October-19-2019 at 2:18pm
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I will try that, thank for the tip! ------------- |
Posted By: stepper459
Date Posted: October-21-2019 at 10:46am
These are friends of mine.... this made the evening news and they fessed up, paid the fine, etc. - generated a lot of discussion at the time. They had done this before in other places, and had spotters on the shore, a couple kayaks ready, and the skier was dressed for it. He let go and swam to shore while the snowmobile continued over to the ice. |
Posted By: MrMcD
Date Posted: October-21-2019 at 2:00pm
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Great Video, that guy is nuts, barefooting when you know there may be ice chunks in the water. My buddy hit a 2' long 2x4 when we were barefooting near dusk. His foot was messed up. I bet an ice cube could do the same. Pretty cool to watch, the people on shore looked amazed also.  ------------- |