Keel Offset R27OB

[Jazzsea]

The stated draft for the R27OB on the RT website is 34" . What value should I enter into the Garmin in order to have a "0" value at the bottom of the outboard? I prefer to know how much water is under my skeg, and not my hull.

 

[KennyMarrs]

Hello Jazzsea,

I typically put 2.5 feet for the keel offset.

 

[MnK2027]

Jazzsea,
If it helps, with the motor all the way down, the skag on my F300 is 14" below the the keel at the transom.

 

[bob daily]

JazzSea, the transducer is measuring depth from the bottom of the transducer to the sea floor. The off set you are looking for would be the difference between the elevation of the transducer and the bottom of the motor when fully lowered. By setting the difference as such it will show you how much water you have under the lowest part of your outboard. Hope this helps. Bob

 

[Jazzsea]

Thanks all. Here in SWFL, we're running in marked channels which can typically be less than 10'. Even in areas of the Gulf, we can have significant shoaling and where we're 5 miles offshore and still in only 10'! I'll go with Kenny's 2'6" number as I would prefer to preserve my lower unit and prop. 🙂

 

[bob daily]

So at a off set of 2'6" on your boat what is the amount of water under the skag at a 0 ft reading?
Which is what you originally requested. Just wondering? Bob

 

[RMarkSampson]

On the Garmin there is a setting for the vessel "draft" and "keel offset." They are two different things. On my R-31S (inboard), I initially set the draft to 2.5 ft and the keel offset to 1 foot as the transducer is approximately 12 inches higher than the keel of the boat. Then I took 10-foot PVC pipe marked at one-foot depth measurements (my modern-day substitute for a lead line) and went out and tested. Being in SWFL - plenty of flat shallow water to compare the depth reported on the Garmin and the actual depth. I even had the opportunity to flat calm water to nudge up on an area that the keel left a slight mark in the sand (I did this on a rising tide just in case). The reading on my Garmin was 0.3 feet. I adjusted the keel offset and believe I am now spot-on for looking at the depth reported on the Garmin and knowing that the depth shown is the actual amount of water under the keel of the boat.

 

[knotflying]

I take nothing for granted. First thing is determine physically your draft with motor down this can be done with boat on trailer and measure from water line to bottom of skeg. Next decide if you want actual depth of water or distance from bottom of skeg to water bed. I always preferred actual water depth and did quick math to make sure I was okay. Example: My water depth is 8 feet and my draft is two feet. I have six feet below skeg. Once you decide on what you prefer for depth. Have boat in water and either use a long pole or weight at the end of a line. Submerge until weight or pole is just touching bottom. Mark at water line and bring it up and measure. This is you depth. Now adjust your keel offset to either give you full water depth or depth from bottom of motor keel. You can also remember you keel depth with motor up, just incase that is necessary. Keep in mind that additional weight and location can change your keel depth so try to take your depth reading when you are fully loaded.

 

[Jazzsea]

Hello Jazzsea,

I typically put 2.5 feet for the keel offset.

Hi Kenny, the manual for the 8612XSV references two potential avenues for keel offset which I was able to find on the chart plotter.

1.) Depth and Anchoring: Only 2 choices "Anchor Height" and "Anchor Scope"
2.) NMEA 2000 Devices: 4 choices "GPSMAP 8612XSV", "Garmin Reactor 40" ,"Garmin GPS24xd", "Fusion MS-RA210"
There is no sonar device listed. Is there another hidden menu I'm missing somewhere? I’m not finding any opportunity to modify a value.

 

[KKRCRACE]

I believe your boat has to be in the water in order for the Garmin to show Keel offset.
KKRCRACE

 

[bob daily]

Go to menu for sonar, you should see what your looking for! Bob