fresh water vs oceans density

Ok new thread on the density of salt water vs freshwater, how much does this effect our boats?
Do they float better? like an egg will sink in fresh and float in salt
Do the go faster? better bite less prop slip

I caught a mutton snapper off the inlet wall while on vacation in Fla. It fought like crazy for a small fish, in fact all the little fish I caught like sand perch just fought like a much bigger fish and I was told because they can pull harder in the salt water than fresh water?

Re: fresh water vs oceans density

Everything being equal, you will not be able to discern the fight in a fish from fresh to salt water. The difference in resistance from the density change is negligable.
On a small private vessels under 100 ton, there is no noticeable difference in performance in pleasure craft. Race boats may notice some difference in performance if you are using great fidelity to measure.
Very large ocean going commercial vessels have a "plimsoll mark" on the side of the vessel that indicates the safe loading level. This level differs from salt to fresh water and from climate to climate. This is partially due to the difference in bouyancy from salt to fresh.






PS- pound for pound, a warm water small-mouth bass can fight with the best saltwater fish!!!!!

Re: fresh water vs oceans density

You boat will sit taller in salt water. Other than that Ive never noticed any other difference in performance. But i only have a 50 on a 17 footer.

Re: fresh water vs oceans density

Ayuh,...

Personal experince,...
Boating here on the Sweetwater sea,+ inland lakes,..
My boat will run 4800rpms @ 42/ 43mph...

Every other year or so,... I boat off the coast of Maine,...
There, on Flat seas,... My barge will run 4800rpms @ 51/ 52mph.....

I attribute it to the tinhull sittng much Higher,+ the cupped ssteel biting Better...

I've gone from Frenchman's Bay to Chemo pond on the same day,+ observed those #s...

Re: fresh water vs oceans density

Bond-o said:

Ayuh,...

Personal experince,...
Boating here on the Sweetwater sea,+ inland lakes,..
My boat will run 4800rpms @ 42/ 43mph...

Every other year or so,... I boat off the coast of Maine,...
There, on Flat seas,... My barge will run 4800rpms @ 51/ 52mph.....

I attribute it to the tinhull sittng much Higher,+ the cupped ssteel biting Better...

I've gone from Frenchman's Bay to Chemo pond on the same day,+ observed those #s...

Click to expand...

Damm Bond-o you always seem to come up with solutions that would elude most people...I have been trying to find a way to get my sled to hit 60 without spending thousands..motors props gear etc..etc.

This will be as simple as mounting at 22p 3 blade dropping the 4.....taking a litte trip across the bar..:redface:...and 60 here i come..Umm that is if i make it over the bar...

And GPS verifyed... Wize One the race is on..

Re: fresh water vs oceans density

Bond-o said:

Ayuh,...

Personal experince,...
Boating here on the Sweetwater sea,+ inland lakes,..
My boat will run 4800rpms @ 42/ 43mph...

Every other year or so,... I boat off the coast of Maine,...
There, on Flat seas,... My barge will run 4800rpms @ 51/ 52mph.....

I attribute it to the tinhull sittng much Higher,+ the cupped ssteel biting Better...

I've gone from Frenchman's Bay to Chemo pond on the same day,+ observed those #s...

Click to expand...

Not noticed as big a difference as that, but my last boat would gain 3-4 kmh and run a higher RPM in salt. But I also gain 1000 ft elevation running in Fresh and that may be part of the difference as well.

Re: fresh water vs oceans density

Freshwater at 20 C has a density of .998 g/cm cubed. Surface seawater at 20 C has a density of 1.025 g/cm cubed. About a 2.5% difference. On a displacement hull, this will be recognizable by the draft difference. On a planing hull, hydrodynamics dominate the equation and there will be negligable resistance difference on the hull with a 2.5% media density difference. Prop efficiency difference with such a small density difference will be difficult to measure or observe outside of a laboratory environment. I believe any considerable performance differences are more likely the result of environma
ental conditions such as wind, tide, surface action (aka foaming), loading, trim, etc..