New instrument transducer install & dead rise

[Jerdavis77]

I'm replacing the transducers on our 1978 Hunter 27 as the old SR Mariner instruments no longer work. I've removed the old thru-hulls and now need to buy and fit the new transducer(s).

This is where the new issues pop up. Using an angle gauge I tried to site what the dead rise of the hull is, and it looks like it's around 25 degrees at the location of the old transducers. I want to avoid glassing over the existing hole and starting over, so now I'm trying to understand the impact this may have and the options. I was interested in going with the DST810. That accommodates up to 22 degrees of dead rise. Airmar support said that it should work, but "the further out of range it is the worse the overall depth will be". A titled element transducer would get me closer, but also double the cost and I don't need this for fish finding. I just want to know the depth.

We sail this boat on Lake Pepin, a wide point in the Mississippi between Minnesota and Wisconsin. The maximum depth of the lake is 59' and I'm mostly interested in knowing from 20' to keel depth.

I'm interested in other's thoughts and hopefully first hand experience with similar installs.

 

[Timm R Oday25]

We have two depth sounders on our Oday 25 . The newer one is mounted inside the hull stuck on with $2.00 worth of toilet wax .
The second older sometimes functioning unit that utilizes an actual through hull has a plug that can be substituted .
I hope this helps

 

[dlochner]

Over the depths you are looking at a few few degrees won't make much of a difference. The critical depths are the shallow ones and the shallower the water, the less error there will be. Someone understands trigonometry could easily calculate the error. I wouldn't worry about it if there is already a hole.

Search recents posts, there has been some discussion about how to enlarge the hole.

 

[Ralph Johnstone]

Following up on @Timm R Oday25 's suggestion of an internal transducer, consider glassing in a small FG pedestal which will eliminate your dead rise completely and then install the sounder with toilet ring, silicone sealant, or your choice of attachment (but not permanent attachment).