Speed in fresh water vs salt water

[snydzy]

Who has had their tug in both fresh and salt water and noticed a difference in speed/performance? Boating mostly on the Great Lakes, I never get the WOT speeds others have posted.... Not even close! 2013 Ranger Tug 25sc, Volvo D3-150G, 1:1.51 Reverse gear ratio, 2 persons, 80 gal. fuel, 30 gal fresh, empty holding tank....2950 RPM .....14.8 knots! Of course, I've got all the extras too, generator, solar panels, and bottom paint.... (I don't believe our mini-dachshund counts :lol: )
Just wondering.....
David

 

[SGIDAVE]

Who has had their tug in both fresh and salt water and noticed a difference in speed/performance? Boating mostly on the Great Lakes, I never get the WOT speeds others have posted.... Not even close! 2013 Ranger Tug 25sc, Volvo D3-150G, 1:1.51 Reverse gear ratio, 2 persons, 80 gal. fuel, 30 gal fresh, empty holding tank....2950 RPM .....14.8 knots! Of course, I've got all the extras too, generator, solar panels, and bottom paint.... (I don't believe our mini-dachshund counts :lol: )
Just wondering.....
David

Hello David,

My 21EC seems to go a slight bit faster in freshwater. Maybe it's not fighting currents regularly present in saltwater conditions....but it DOES get 50-100 rpm higher WOT in FW, so I think it's a REAL difference.

You HAVE bottom paint...but is there ANY growth on your (boat's) bottom? Even a little slimy accumulation can slow you down. Is 14.8K the BEST you've ever gotten?

dave

 

[S. Todd]

Like you we boat primarily on the great lakes with a 2015 R25SC with the same engine as your Tug. 14.8 knots is 17 mph. I get 18 mph with full water and fuel. When I have only half a tank of fuel and water that speed goes up to 19 mph. I find it important to find the sweet spot with the trim tabs, too little or too much tab and you can loose a mph or more. I have heard that bottom paint will cost you 1 mph. My bottom is not painted and is completely clean when the week begins. I do not have the generator but do carry a bike on a roof rack (only 15.5 lbs but there is some wind resistance) and an inflatable Zodiac rolled up in the cockpit. There is no question that weight makes a difference because on my dealer demo run without spare anchor and rode, and a weeks worth of clothes, food, galley ware, etc. I got another mph at top end. I count my two dogs in the weight figure because together they weigh just over 80 lbs and bring their toys and food. It is my understanding that because salt water is more dense the boat floats higher and the speed should increase somewhere between 5 and 10%, but I have not personally tested it.

 

[snydzy]

Just following up.... We trailer the Tugster.... Bottom is immaculate. On the other side of the spectrum, I can idle and do about 3.5 knots.....I do a lot of shifting between neutral and drive when navigating crowded channels and boat slip approaches... Seems a little fast. I've heard others say: better low end performance in fresh water, better upper end on salt water...So I thought I'd ask.
David

 

[oscar]

Specific gravity....ring a bell? Not sure if it matters....

 

[R Baker]

Fresh water or not, I find I go a bit faster when the heading is south - must be down hill. :lol