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deadrise for thru-hull

davisr

Member III
I am in the process of upgrading the electrical system and electronics for my E25. I'm thinking about purchasing the new Garmin GPSMap 541s while the $100 rebate is in place. I'm looking a several different thru-hull transducer options. The existing thru-hull is about three feet forward of the centerboard trunk and is centered. It does not point vertically, but at an angle, since the hull, at the point, is beginning to slope upward in its rise toward the bow.

Most of the thru-hull transducers sold by Garmin are just your regular thru-hulls. I would rather go with one of these rather than with the more expensive kind that is designed with a compensating angle within the structure of the thru-hull itself.

Just wondering what others have done with their thru-hull installations when faced with this issue.

Thanks,
Roscoe
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Choosing Where to Put It

My experiences, FWIW.
On our prior 26 foot fin keel boat, I had to figure out where to put the DS transducer. Forward hull section had a quite a V to it.
I finally re-focused my thinking on the fact that the boat seldom went faster than 6 kts, and under power in worrisome shallow waters was usually motoring less than 2 kts. (We did over 8 kts in open water with the chute up, but that's a whole 'nother story.)

The time difference in getting a depth warning from a location ahead of the keel and about 10 feet further back, behind the keel was maybe a second. Give or take. I figure that if the underwater "wall" that you are concerned about hitting is that abrupt, the presence of a tree growing just in front of the bow is a bigger giveaway than the chime from your DS alarm. ;)

So I glued the transducer to the inside of the hull on centerline under the front part of the cockpit. Worked great for the ten years we sailed that boat. We never ran aground "unexpectedly" and that's the whole purpose of it, IMHO.

We did ground a couple times while in very shallow waters, but the location of the transducer was not to blame... :rolleyes:

Wherever you install it, just be sure that you are not too close to the keel, i.e. that the cone of sound radiation is clear of the keel. The install instructions will mention this, too.

Regards,
Loren
 
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Emerald

Moderator
How about a P79 in-hull transducer? They let you compensate for something like 22 degrees of dead rise, and no holes to worry about. This unit works with my Garmin chartplotter, and hunch is it would work for you also.
 

wolly bugger

Member II
thru-hull

Hi Roscoe,

I just ordered the 540S (I got it for under $500). The 541S looks a little better but the price was perfect for me.

The transom mount thru-hull that come with it can also be installed inside the hull and shot thru the fiberglass, so no hole to drill. You lose a little bit of range and maybe some accuracy, but at that point there is no worry of running aground. You can find all the specs in the installation guide on their web site.

Mine should be here in the next few days, can't wait to play with it. :egrin:
 

davisr

Member III
Thanks Fellas for all the words of wisdom. Just wondering . . . has anyone ever installed a transducer with a fairing block to account for the deadrise? I found these pictures on Google Images.

Roscoe
 

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davisr

Member III
If I'm going to install a new thru-hull (in the old thru-hull hole) it looks likes my other option is the tilted mount transducer that is manufactured by Airmar for Garmin, Raymarine, and others. They cost about $60 more than a normal bronze thru-hull, but they save the expense and hassle of dealing with the fairing block. Has anyone had good experiences with these?

Thanks for the help,
Roscoe
 

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