FRESH vs. SALT?

[wolf IV]

I run in salt water and do all my testing in saltwater as its close to me (like 3 min) away from my garage.. my question is : WILL A BOAT RIDE DIFERENT IN FRESH WATER AS TO SALT? ALSO, CAN THE BOAT POTENTIALLY GO FASTER ON FRESH OR SALT WATER? AND WHY....

[ozzie-crawl]

i think there has been a few discusions on salt v fresh.
i know a guy who runs gas boats. he was tuneing a hydro in fresh water and constantly running in the mid 70 mph range,went racing in salt and couldnt get more than 68 mph on same setup,went back to fresh and was back in the mid 70s
not sure if one is ultimatly quicker than another but diffrent setups are probably needed

[hydromaddicted]

A given volume of saltwater will have more mass than the same volume of fresh water.Thus, it's a little harder to push through for boat and prop.

[Xcesive8]

Thats wierd scott, cos i always thought salt water was more buoyant than fresh?
Recently we went up to brissy with our gas boats and used the brissy clubs freshwater lake, and everyone of the guys from gold coast was saying there boats were a lil slower.

I wonder if you sat a boat in fresh, took a mesurement of water line down the side of hull, if it would be any difference at all to how it sat in more buoyant salt?

:confused2:

[hydromaddicted]

Yes salt is slightly more boyant,when it comes to speed alot depends on the actual salinity of the water.

[ozzie-crawl]

i think its the density of the water that makes the diffrence not the bouyancy

[ozzie-crawl]

lol bit slow with my replie :sleep:

[wolf IV]

i think its the density of the water that makes the diffrence not the bouyancy

you all hit my question(s) on the nose.. i was battling boyency vs. density...??

[wolf IV]

So whats the verdict? I run 67 in salt , will i hit 70 in fresh!!!:hug1:

[Xcesive8]

Seawater
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Sea water in the Strait of MalaccaSeawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5%. This means that every kilogram (2.2lb), or every litre, of seawater has approximately 35 grams (1.2 oz) of dissolved salts (mostly, but not entirely, the ions of sodium chloride: Na+, Cl−). The average density of seawater at the ocean surface is 1.025g/ml; seawater is denser than freshwater (which reaches a maximum density of 1.000 g/ml at a temperature of 4 °C (39 °F)) because of the salts’ added mass. The freezing point of sea water decreases with increasing salinity and is about −2 °C (28.4 °F) at 35 g/l.[1]


:unsure:

[BakedMopar]

The pond I run on has salt water entering a fresh pond. At that end of the pond I have broken at least half a dozen props.

[ozzie-crawl]

with surface drive props and hulls hardly touching water does bouyancy even come into play while the boat is running,i think the dencity is they decideing factor, the more dence maybe the less prop slipp but then is it harder for the prop to cut threw?

[wolf IV]

with surface drive props and hulls hardly touching water does bouyancy even come into play while the boat is running,i think the dencity is they decideing factor, the more dence maybe the less prop slipp but then is it harder for the prop to cut threw?

I DOUBT BOYENCY HAS ANY PLAY AT HIGH SPEEDS W/ LOW DRAG BOATS. my theory was/is: Fresh water may be a little , key (little) harder to get on plane( less boyency), but a higher top speed . Saltwater easier to get on plane but lower speeds due to the density. So is this fair to say?

[ls1fst98]

well think of it this way, when a full size boat tries to do full speed and record runs what do they do them in? fresh or salt? most i have ever seen is salt. i would think that with the time and effort and research that top racing teams put into these types of runs this question would have been brought up, researched, and answered. just my idea. not sure if its right or wrong.

i would assume that being salt water is more dense than fresh, the prop would both encounter higher friction rotating, but allow greater push so to speak.

::edit:: but then again unlimited hydros run in fresh as well as drag boats. a lot of that is due to water conditions though.

[BakedMopar]

My sv27 runs a tad hotter on salt water also.

[wolf IV]

hmmm...? again, great point(s) and ideas, but still someone has to have a direct answer..? ill be running in fresh this next weekend and will know without a doubt wich is actually faster .. i guess..? id also like to know if theres a trim adjustment diference? two years ago when i ran a mono at legg lake for the first time it was real aparent that at high speeds it was looser/dryer...! but thats cuz id only ran in salt for two years prior to hitting legg lake. it was quite apparent though.. i guess we shall see...

[wolf IV]

My sv27 runs a tad hotter on salt water also.

thats what i think.. more drag/prop bite do to salt density...as stated above.

[teach]

Just guessing here, no facts whatsoever.

I would think a properly tuned boat would run faster in salt water's higher density. To me less slip would occur.

That's way to much thinking for one day....back to watching *!***!***!***!**. :zip-up:

[ls1fst98]

i can take my sv to the pond then to the saltwater all in a matter of minutes and can at least say which woul dbe faster, at least for my setup. but that still doesnt answer the question.

anyone have adegree in fluid dynamics and can answer this definatively??

[domwilson]

http://www.newton.dep.anl.gov/askasci/eng99/eng99631.htm

http://www.boatfix.com/how/props.html

"6. Salt water is more buoyant than fresh water; this may cause some hulls to run faster than identical freshwater setups."

[egneg]

http://www.newton.dep.anl.gov/askasci/eng99/eng99631.htm


I am in a dark room and I think someone is full of :icon_bs:

[tiqueman]

No degrees in fluid dynamics but I can say this. I used to take my gassers back and forth between salt and fresh and I did need to make trim adjustments between the 2. I never Gps'd any of them, but ran them long enough to know when something wasnt right, didnt sound right or didnt look right inthe ride attitude.

I will also say that being an extremely active year round wakeboarder... had to put that year round in for you guys with frozen ponds right now.... I notice a huge difference of the ride attitude of my boat between fresh and salt, both conditions running at the same speed. Not having trim adjustments on a tournament wake boat, I have to adjust my ballast accordingly between the two to keep the wake shape the way we want it.

So Wolf, I will have to say that there very well could be some trim adjustment needed.... but Im no expert, just sharing my experiences.

[obrien]

salt water is faster than fresh water. I have plenty of time testing the same boats in both types and salt water is always faster. This is based on full size boats that I have run at work. I don't have a degree in fluid dynamics, but I do have alot of seat time.

[blizard05]

Let me say this, a lot has to do with water conditions, calm, slite ripple, or chop, can't compare without the same water conditions. Most boats will go faster with a little chop,than flat calm water

[wolf IV]

no degrees in fluid dynamics but i can say this. I used to take my gassers back and forth between salt and fresh and i did need to make trim adjustments between the 2. I never gps'd any of them, but ran them long enough to know when something wasnt right, didnt sound right or didnt look right inthe ride attitude.

I will also say that being an extremely active year round wakeboarder... Had to put that year round in for you guys with frozen ponds right now.... I notice a huge difference of the ride attitude of my boat between fresh and salt, both conditions running at the same speed. Not having trim adjustments on a tournament wake boat, i have to adjust my ballast accordingly between the two to keep the wake shape the way we want it.

So wolf, i will have to say that there very well could be some trim adjustment needed.... But im no expert, just sharing my experiences.

so compared to salt water to fresh what kind of trimming was taken?

[tiqueman]

Sorry wolf, been away from my computer. If I remember correctly, again, this is on gassers, 52" and up. My cat would run a two blade in salt and a 3 in fresh and I would run the strut lower in fresh. My Deep V, I would leave alone for the most part. it would run a tad more wet in fresh but not enough to really take the time to make adjustments. I sport ran both boats so I never went die hard test and tune to get optimum performance. Again, it was based more off of sound and what the hull was doing... along with runing w/ friends boats and knowing how much faster or slower I was compared to them in previous conditions. Also, for testing conditions, both fresh and salt running were in extreme glass conditions.

Being that our electrics are much lighter and ride much less in the water, Im not sure whats going to happen. Maybe there wont be enough "wet hull" to make a difference. I dunno???

[wolf IV]

Sorry wolf, been away from my computer. If I remember correctly, again, this is on gassers, 52" and up. My cat would run a two blade in salt and a 3 in fresh and I would run the strut lower in fresh. My Deep V, I would leave alone for the most part. it would run a tad more wet in fresh but not enough to really take the time to make adjustments. I sport ran both boats so I never went die hard test and tune to get optimum performance. Again, it was based more off of sound and what the hull was doing... along with runing w/ friends boats and knowing how much faster or slower I was compared to them in previous conditions. Also, for testing conditions, both fresh and salt running were in extreme glass conditions.

Being that our electrics are much lighter and ride much less in the water, Im not sure whats going to happen. Maybe there wont be enough "wet hull" to make a difference. I dunno???
thanks bud!! well i ran today up at lake forest lake!! all i can say is it was perfect.. A DREAM.... PROPPER CHOPPER.. GET OVER THERE ASAP!!! so i conclude that with the maritimo it ran 65 mph every time ( pretty much).. this is 2 mph slower than in salt. i knew it right away. also the boat seemed to ride wetter oot of the hole as exspected due to a lack of bouyency. but, was way dryer on full throttle once i got my speed up..? if i didnt let up on the throttle it would start walking . infact i swapped up trying to see if she would pull out of the walk her self.. no such luck! she still ran good , but if i was to run in frsh regularly i would have to drop the angle just a tad on the stingers. ill post 3 videos questek took of the runs/ crash... joe, thankyou again . we will have to do it again .. SOON!! :)

[wolf IV]

http://www.youtube.com/watch?v=sLh8g5mz9_k IM GONNA POST THESE HERE DUE TO THE THREAD STARTED, AND TO OBSERVE THE RIDE OF THE HULL ON FRESH WATER ALONG WITH GPS-ED SPEED..

[questtek]

Glad you enjoyed running on my Lake. Yes indeed, PropperChopper needs to bring a few of his toys down too! My 16' electric recovery boat had a bad connection but all is fixed and ready for the next runs. Hopefully we can get more FE guys from around the local area to join us. I will be at the CES show in Vegas this week but the following week is open for some more fresh water runs.

[properchopper]

OK, been meaning to get down to Lake Forest; will plan a trip soon- I've been tuning for WW VI but have some play boats as well. Looks like a nice pond !!

[Mel279]

I've been running my triton using an scorpion outrunner 4020 1390kv, gets hot pretty quick and try to gets more runtime but in the end burnt the winding, that was on a fresh water pond. Then I try my other outrunner on salt water, longer runtime and motor just warm.

[wolf IV]

i've been running my triton using an scorpion outrunner 4020 1390kv, gets hot pretty quick and try to gets more runtime but in the end burnt the winding, that was on a fresh water pond. Then i try my other outrunner on salt water, longer runtime and motor just warm.

weird....

[Mel279]

Yes salt is slightly more boyant,when it comes to speed alot depends on the actual salinity of the water.
Maybe this actually true

[Xcesive8]

weird....


Yep me too..

I run my HPR in fresh everything heats up fast.
Run it in salt, seems to go better and stays cooler.

YEP

Weird

[wolf IV]

Well nothuing is adding up for me... My runs were slower in fresh, looser, and cooler...? Ill run again in a few weeks to get better readings and two diferent mph readings, temps ecc... Then ill do the same in salt in the same conditions. But the water will be cooler in salt so temps will not be the same..

[Fruity]

Guys,
this is just a thought, but maybee the salt is making the salt water more conductive, helping in the heat transfer process?

Dunno...???

Cheers...Tim.

[questtek]

Well nothuing is adding up for me... My runs were slower in fresh, looser, and cooler...? Ill run again in a few weeks to get better readings and two diferent mph readings, temps ecc... Then ill do the same in salt in the same conditions. But the water will be cooler in salt so temps will not be the same..

I had a chance to give this some thought and think you are on the right track based on your saltwater harbor run and the freshwater run on my lake.
It appears that with the higher density of seawater the prop "digs" in more thus a higher speed by several percent. If this were the only factor we could easily confirm this by measuring the density of the seawater at Dana Point and comparing it to the fresh water in my lake. Density is easily calculated in you know temp and salinity. (http://www.csgnetwork.com/h2odenscalc.html

The Dana Point saltwater is at 60 F and 34 parts per thousand for salinity giving a density of 1.025106 (gm/cm3)

The fresh water in my lake has a temperature of 64F and salinity near 0 giving a density of 0.998666 (g/cm3)

This is a density difference of 2.56%, which potentially suggests that you would go 2.56% faster in seawater. We measured your speed consistent at 65 MPH at the lake, which, if our assumptions were correct, would be 2.56% x 65MPH or faster by 1.7 MPH in the Dana Point Seawater. This would put your Dana Point runs at 66.7 MPH and I believe this is close to what you have been recording. The math Gods have been good!

Now, in terms of the cooling there have been several views expressed in this thread. I tend to agree with yours and we can confirm that with my Eagle Tree logger. You say fresh water permits cooler running. I agree since fresh water has a higher specific heat (the amount of heat needed to raise the temperature of 1 kg or water by 1 degree C). The addition of salt reduces this heat storing capacity.

You posed some good questions but let me throw another in, air temperature. At the speeds these FE’s are running air drag becomes a major factor. Naturally you want to reduce the frontal area of the boat, make it streamline and have the lowest Cd, Coefficient of drag, possible. Cool air has higher density than warm air. Running in higher air temps would thus reduce air density and thus air drag also providing slightly higher speeds.

I’ll book us a trip to Dubai where the salinity of the Arabian Gulf is 30% higher than the open ocean due to evaporation and the air temps are well over 100! Those factors alone should see your boat clocking 70 MPH plus!

[Jeff Wohlt]

All I know is my real bassboat runs faster in cold water than warm.

I am sure it is running cooler at the motor as well and maybe the cool air intake is also adding to lower intake temps which increase power but Seems I am at the same RPM yet MPH is higher.

Hey....funny bit. My buddy has a new Champion 20' bassboat with a 225 Merc and he was fishing in the winter and was running down a cove and the motor suddenly kicked up so he pulled the kill swtch and his boat was sliding over ICE and sideways skiding until it slowed down and broke back through. Then he had to use his new FG hull to be an ice breaker until he got to the water again. Couple of chips in the nose V but nothing big. Hearing him tell it...well I was laughing so damn hard but just freeked the crap out of him. Well versed high speed driver too. He said all he could do is hold on to the side rails and take the ride.

[questtek]

[QUOTE=Jeff Wohlt;150090]All I know is my real bassboat runs faster in cold water than warm.

Colder water has a higher density and, if you go along with the higher the density the more prop dig theory, it would make sense. Your comments on running cooler are also quite valid. Loved the ice story!

[Jeff Wohlt]

I will say, the engine is just purring like a kitten when cold like that. Suckng down massive air with a Big Bore V-6 2 stroke with a big carb per cylinder.

After Bill Seebold Sr. worked on the prop for me the lift is crazy and top end is up 5-7 mph with the same prop. Probably the last prop he engraved his name on. He lived 1.5 hours from me and I went to his house. Should have seen the old mercs and racing outboard motors he had...I need to speak with Tim and see where it all ended up. Bill, jr...many time World champ boat racer only wants to play golf now.

The new outboards are now beginning to dominate motors around here in HP boats. 28' foot cats aournd here with twin 250 Mercs are running 115 mph down the lake with ease and 4 people in the boat.

[obrien]

what motor are you running on your boat Jeff? I acutally built a 30' Spectre Cat with a pair of 300 mercs for Mike Seabold a few years ago. I got to talk with him a few times as well as Bill when they came to the shop. I couldn't imagine the things they must have at their shop.