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Speed Over Ground vs. Speed Thru Water.

Which is a more accurate measure of your boats speed when trolling for the big Stripers? Obtained the new GPS (Simrad NSS7) halfway threw the 2014 fishing season and trying to make sure I am in traveling at the right speed. 2.5-3.5 knots.


The boat RPM are 10-15K rpms if memory serves me correctly from prior seasons.


Thanks in advance for all comments
 

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Yup. Speed thru water is what he fish experience. Unfortunately, I just have SOG, as my paddle wheel quite 12 years ago, and I removed it.
 

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The fish are in the water; the boat is in the water. STW will tell you how fast your boat is moving relative to a fish's location. Your tachometer should yield a fairly consistent STW (discounting the effect of wind) for trolling purposes as both you boat and the fish in the same location will be subject to the same effect from whatever current is flowing. Paddlewheels are good for STW when trolling (most lose some accuracy at higher speeds), but your tach can be just as effective, as the same rpms on the same boat loaded and trimmed the same will yield a consistent STW.
 

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As stated, speed through water gives the paddle tail it's action and speed of bait swimming in water. The boat speed number should be a starting point as current and turns effect bait speed. Learn the angle of boat rod lines when the fish are biting. A lesser angle and you are to slow, greater angle to fast.
 

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Your GPS ( SOG ) is perfect - in a small pond. In the open bay - current will effect your speed through water up to 1.5 knots.

First thing to remember - current is water moving horizontal - tide is water moving vertical. Often people will say " tide is running fast " but really it is current.

The raising tide ( flood ) will bring incoming current - this tends to move NNE around here. The falling tide ( ebb ) will bring outgoing current that runs SSE.

This factors greatly into the SOG displayed on your GPS.

The best example is a people mover - often seen at airports. Try to picture this in your head. You walk beside the people mover and your friend walks on it. You both walk the same pace - but he gets far ahead of you.

This would represent trolling with a strong current. The GPS might show 4.0 ( friend on people mover ) but speed through water would be 3.0 ( you walking beside ). Slowing boat to 3.0 on GPS will mean lures are at 2.0 - likely too slow right now.

Now , flip this around 180* and picture your friend walking against the people mover. You'll be far ahead of him - this represents trolling into strong current.

GPS might show 3.0 but lure speed is really 4.0 - likely touch fast right now.

Trolling east to west takes some of current out of speed but boat ( SOG ) will still be effected. Try aiming straight for something on shore. In strong current - you'll be carried up or down the bay - adding to SOG by about 1/2 knot. When current is running - I show 3.3 on GPS but my lure speed is about 2.9 -3.0 , just right.

I can observe current strength by GPS ( SOG ) - it will slow as current weakens. When slack water - GPS will read SOG accurate , yet often fish do not bite that time.

Old school is to observe a lure close to boat if unsure of speed. Spoons should wobble / dive but not spin. Shad tails should swim but not twist.

Next thing to complicate matters is wind. If with current - easier to adjust to. Going into current / wind means moving RPM up slightly to off set wind pushing boat backwards.

If opposite - I'll bring throttle back at times - to offset speed gain by wind pushing boat forward.

If you do get a paddle wheel - be sure to calibrate by GPS on straight course in calm waters. The " pond " at Sandy Point ramp is great - start far back near police boats. The jetty area does have slight current at times.
 

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Your GPS ( SOG ) is perfect - in a small pond. In the open bay - current will effect your speed through water up to 1.5 knots.

First thing to remember - current is water moving horizontal - tide is water moving vertical. Often people will say " tide is running fast " but really it is current.

The raising tide ( flood ) will bring incoming current - this tends to move NNE around here. The falling tide ( ebb ) will bring outgoing current that runs SSE.

This factors greatly into the SOG displayed on your GPS.

The best example is a people mover - often seen at airports. Try to picture this in your head. You walk beside the people mover and your friend walks on it. You both walk the same pace - but he gets far ahead of you.

This would represent trolling with a strong current. The GPS might show 4.0 ( friend on people mover ) but speed through water would be 3.0 ( you walking beside ). Slowing boat to 3.0 on GPS will mean lures are at 2.0 - likely too slow right now.

Now , flip this around 180* and picture your friend walking against the people mover. You'll be far ahead of him - this represents trolling into strong current.

GPS might show 3.0 but lure speed is really 4.0 - likely touch fast right now.

Trolling east to west takes some of current out of speed but boat ( SOG ) will still be effected. Try aiming straight for something on shore. In strong current - you'll be carried up or down the bay - adding to SOG by about 1/2 knot. When current is running - I show 3.3 on GPS but my lure speed is about 2.9 -3.0 , just right.

I can observe current strength by GPS ( SOG ) - it will slow as current weakens. When slack water - GPS will read SOG accurate , yet often fish do not bite that time.

Old school is to observe a lure close to boat if unsure of speed. Spoons should wobble / dive but not spin. Shad tails should swim but not twist.

Next thing to complicate matters is wind. If with current - easier to adjust to. Going into current / wind means moving RPM up slightly to off set wind pushing boat backwards.

If opposite - I'll bring throttle back at times - to offset speed gain by wind pushing boat forward.

If you do get a paddle wheel - be sure to calibrate by GPS on straight course in calm waters. The " pond " at Sandy Point ramp is great - start far back near police boats. The jetty area does have slight current at times.
This all sounds very complicated, I think I'll just get one of my LMB outfits, find some birds and just shake it up and down like a retard until something bites...PURA VIDA!... :usa:
 

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On my boat, I only have SOG, but I have figured that between 900-1000 on my Tacometer is just about right based on how my umbrella's are running. It has been as slow as 1.6-1.8 into the current and as fast as 4.6-4.8 with the current, but I usually try to go east to west.
 

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Your GPS ( SOG ) is perfect - in a small pond. In the open bay - current will effect your speed through water up to 1.5 knots...

This would represent trolling with a strong current. The GPS might show 4.0 ( friend on people mover ) but speed through water would be 3.0 ( you walking beside ). Slowing boat to 3.0 on GPS will mean lures are at 2.0 - likely too slow right now...
You said this backward, 27 sailfish. Your speed through the water is a function of your screw RPMs (and wind), but not current. The current will affect your speed over the ground but not speed through the water. The entire body of water, which includes your boat, lines, and fish is all moving together, so there is no relative movement from current among those things. There is relative movement of all of those things relative to the bottom, however.

Extreme example: If you were trolling at 4 knots against a 5 knot river current your lines are still going to trail behind your boat - not out in front of your boat. If you were anchored in the river (SOG = 0) the lines would trail behind you like you were making 5 knots. If you were trolling at 4 knots the lines would trail behind you like you were making 4 knots, but your SOG would be negative 1 knot.
 

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Speed Through Water Indicator for Trolling - Stretch 25 WWB

My friends and I almost always put a Stretch 25 WWB on a medium light rod. We watch the action of the rod for the proper vibrating action. If the Stretch is not vibrating right, we adjust the speed until it vibrates the rod tip. Trolling with the current will require a faster SOG to get the Stretch to vibrate (and the shad tails on all the other lures will vibrate also). Try this beside the boat and you should see what happens to the Stretch and the shad tails at various speeds. And the Stretch catches fish as well.

Tom
 

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An old trick is to watch the bend in your poles. Its is a pretty accurate guide once you have your speed figured out. It is also why many troll e-w to minimize current effects & to not have to significantly alter speed with or against current. As the biguns leave your 4 mph will be fine. I've even caught keepers stripers @ & mph on an oustide turn ( while fishing for spanish).
 
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