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  #1  
Old 05-22-2016, 09:51 PM
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Depth finder keel offset

Depth Finder question. Who is using a keel offset? If so, are you having measure the depth below the boat or total water depth?

So the instructions that came with it imply you should set the keel offset to measure water depth below the boat. It seems to me that it would be more useful to have it set to measure water depth from the surface.

Just wondering what everyone else does.
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  #2  
Old 05-22-2016, 10:18 PM
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CruisinGA CruisinGA is offline
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I don't care how far it is from the bottom to the surface, I care about the distance between the bottom to my prop
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  #3  
Old Yesterday, 02:08 PM
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I guess but I know my draft is 2'.
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  #4  
Old Yesterday, 02:27 PM
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I set the keel offset at 2' then set the alarm for 3'. That's 5' total depth. I can take the time to add 2' if I want total depth but what I'm worried about is hitting bottom so knowing that distance at a glance without the thought of subtracting is important to me.
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  #5  
Old Yesterday, 02:31 PM
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manufactures spec the draft when empty.

for example, my x2 draft is spec'ed @ 27" when empty. Add a boat full of people and full ballast and the value 8 - 10 inches different... or at least i am estimating that based on how submerged my swim platform is...

Thing is, running gear is expensive. Do you really want to be estimating the draft at the moment?
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  #6  
Old Yesterday, 03:25 PM
ctmaloney ctmaloney is offline
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Quote:
Originally Posted by _ds_ View Post
manufactures spec the draft when empty.

for example, my x2 draft is spec'ed @ 27" when empty. Add a boat full of people and full ballast and the value 8 - 10 inches different... or at least i am estimating that based on how submerged my swim platform is...

Thing is, running gear is expensive. Do you really want to be estimating the draft at the moment?
^^^ that doesn't matter if you're just concerned about depth of running gear. Since the transceiver is a fixed distance from the bottom of the boat. But it makes the case for setting the offset for below the boat.

For example, if the draft is 2' and the transceiver is mounted in-between so 1' below the waterline but 1' above the bottom of the boat.

If its reading 10' the water is really 11' and the bottom of the boat is really 9'. So, you would either add or subtract 1' based on what offset you'd want to do.

But if you add a bunch of weight to the point the draft is now 3' the transceiver is still 1' from the bottom of the boat but its now 2' from the waterline. So a 10' reading would still be 9' under the boat for a -1 offset, but would show 11' for water depth with the +1 offset when it is really it should be 12'.

Now you would still get the right number under the boat by subtracting your spec'd draft 11' - 2' = 9' but your water depth would be all wrong.

Clear as mud...
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  #7  
Old Yesterday, 10:32 PM
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jakethebt jakethebt is offline
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Good discussion. This is why I posted the question.

So question... Some MCs come with factory depth finders. What are they set to?

Before reading the instructions on a new depth finder, I assumed that most depth finders are reading true water depth and I would always need to take my draft off in my head. Anytime I am running in less than 5 feet I should be alert or concerned.

Sounds like folks here are more concerned with the exact clearance under the running gear.
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Old Yesterday, 11:01 PM
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I would rather get nervous thinking it's 2 feet deep when it's really 4', than think it's 4' when it's really 2.
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  #9  
Old Today, 07:48 AM
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I have mine set with no Keel Offset and the alarm sounds at 3'. That means if you have roughly a foot of running gear, you still have 2' foot under you. After all, the only reason I installed a depth finder is to protect my prop
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