Water temperature?

[DroopyDog]

Hey all. I'm curious if the speed or performance of the boat can be affected by the temperature of the water. Its sort of a project I'm doing. Also, can you please cite your sources? Thanks.

 

[stevieray]

Re: Water temperature?

Droop - do you mean just how it would affect hull/water contact? And over what range of temperatures are you thinking?

 

[DroopyDog]

Re: Water temperature?

I mean the general performance of the boat: speed, maneuvability, endurance, and buoyancy. And I'm talking around just above freezing point, to just below boiling point. If your wondering, I'm experimenting with a model boat.

 

[stevieray]

Re: Water temperature?

Well, from basic physics, density of water from 32F to 205F changes about 4%, so the same boat would essentially be 4% "heavier" in water at 205F. The viscosity changes from 1.75 cp at 32F to 0.291 cp at 205F, so the hull would be more "slippery" in warmer water than cold, but not to that great a degree when hull is at high enough speed to be on plane (turbulent flow). How would that affect performance? In something the scale of a large ship, you could probably measure it - on a model scale, I'd say the effects would be unnoticeable.

 

[JB]

Re: Water temperature?

If the water temp drops below 0*C performance is very poor. From 0*C to about 3*C water density decreases and drag may decrease, but I doubt that it would have measurable effect.

 

[ziggy]

Re: Water temperature?

i don't think this is the kind of performance yer talkin about, but it is a speed and perfromance issue.
if a mercruiser is has a 143*F t-stat. and is operated for long periods of time in cold water at very low rpm, ie trolling. install a 160*F t-stat. this improves combustion under such operating conditions. gives smoother low-speed operation and reduces crankcase dilution caused by condensation. avoid wot when useing a 160*F t-stat with such engines. per clymers mercruiser sterndrive shop manual, 1964-1985.
so assumming this is true the reverse would be that operation at low speed in cold water (it don't say how cold) would give somewhat erratic operation and produce condensation that will dilute yer oil with water. i recokon that could effect perfromance and speed. and wear and tear. guess it's more like low speed effect on performance. just some more food for thought i guess........

 

[JasonJ]

Re: Water temperature?

One thing I notice is my prop bites and holds a lot better in colder water. I have also seen slightly higher speeds in colder water. I can think of two reasons for that. When my water is 80 degrees, it is usually in the middle of summer an the temps are in the high 90's plus. When my water is 60 degrees, the air is usually in the 40s and 50s, and colder as the year progresses. The engine runs better in the older, denser air.

The other reason is colder water is more dense, the prop slips less, and the boat is more bouyant and is easier to get on plane and stay on plane in the cold water. These effects are very noticeable on my boat, especially speed and prop bite. I am guessing the actual density numbers are not that different between the temp extremes, but there has to be something to it considering the performance difference I see.

 

[Texasmark]

Re: Water temperature?

I like your answer JB, d but Ice kites are pretty fast.

Mark

 

[ricksrster]

Re: Water temperature?

I've noticed when the water is 0 degress C, that even rocks don't sink in it.

 

[troypolla]

Re: Water temperature?

Salt water would have an effect on bouyancy. It reduces the freezing point of water. It does seem to have an effect on how high the boat sits in the water.

 

[bruceb58]

Re: Water temperature?

The temperature of the air will have way more effect than any temp difference in water would be. The density of water between 50F and 80F is negligible. It is only 0.4%

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