Replacing Datamarine Depth and doing in-hull transducer

[c and c 30]

I had to replace my non-functioning datamarine depth finder on a C and C 30 1982. I searched all the forums and so forth and found that the best option was a Moor electronics replacement, as they are the only company that makes a 4-inch gauge, and I had absolutely no interest in doing fiberglass work. In addition, I didn't want to deal with the thru-hole, so I did alot of reading about inside-hull mounts and water boxes. I tried a yogurt container, buth that did NOT work. The trick is to use something conical in shape to allow for the conical sonar beam of the transducer. I found a great solution.

For those of you in the same predicament, here are the steps for what I did, which turned out great.

1. Clean inside of hull where you plan to put transducer. Use Scotchbright and acetone.
2. Attach wiring of Moor electronics depth finder so that you can test transducer.
3. Put a large glob of vaseline on the transducer and then test the hull area for good acoustics. Vaseline is really easy to use for this purpose and, as discussed below, a good predictor of your water box performance. Mark the spot where you got good readings.
4. Get an 18 ounce red plastic cup-the kind the college kids use at keg parties
5. Cut out a round part of the middle of the bottom so that the transducer will fit there later.
6. Epoxy the cup rim to the hull.
7. After it has cured, use silicone sealant around the epoxy.
8. Fill the cup with mineral oil. As turns out, this is a petroleum product which has great acoustic properties. Vaseline is rather similar, so if it worked with vaseline, it will probably work with mineral oil.
9. Insert the transducer and seal it with silicone.
10. Enjoy your new depth sounder.

Also, for the speed, I got a speedpuck and used commercial velcro to attach its holder over the old one. The speedpuck is terrific. Now i have depth and speed without dealing with holes in the hull or fiberglass repair.

The only question is whether the mineral oil will eventually degrade the silicone. I called 3M requesting advice on what to use instead and they said to wait and see because they think it might be OK.

I attached photos.

 

[onecoolair]

I had to replace my non-functioning datamarine depth finder on a C and C 30 1982. I searched all the forums and so forth and found that the best option was a Moor electronics replacement, as they are the only company that makes a 4-inch gauge, and I had absolutely no interest in doing fiberglass work. In addition, I didn't want to deal with the thru-hole, so I did alot of reading about inside-hull mounts and water boxes. I tried a yogurt container, buth that did NOT work. The trick is to use something conical in shape to allow for the conical sonar beam of the transducer. I found a great solution.

For those of you in the same predicament, here are the steps for what I did, which turned out great.

1. Clean inside of hull where you plan to put transducer. Use Scotchbright and acetone.
2. Attach wiring of Moor electronics depth finder so that you can test transducer.
3. Put a large glob of vaseline on the transducer and then test the hull area for good acoustics. Vaseline is really easy to use for this purpose and, as discussed below, a good predictor of your water box performance. Mark the spot where you got good readings.
4. Get an 18 ounce red plastic cup-the kind the college kids use at keg parties
5. Cut out a round part of the middle of the bottom so that the transducer will fit there later.
6. Epoxy the cup rim to the hull.
7. After it has cured, use silicone sealant around the epoxy.
8. Fill the cup with mineral oil. As turns out, this is a petroleum product which has great acoustic properties. Vaseline is rather similar, so if it worked with vaseline, it will probably work with mineral oil.
9. Insert the transducer and seal it with silicone.
10. Enjoy your new depth sounder.

Also, for the speed, I got a speedpuck and used commercial velcro to attach its holder over the old one. The speedpuck is terrific. Now i have depth and speed without dealing with holes in the hull or fiberglass repair.

The only question is whether the mineral oil will eventually degrade the silicone. I called 3M requesting advice on what to use instead and they said to wait and see because they think it might be OK.

I attached photos.

That Dixie cup will not last very long. While your design idea seems good it is not going to work for very long. Think about modifying you idea by using a short piece of upvc pipe with a end cap. Cut a slot in the top of pipe to allow for the cable to lay. Then a slot in the cap. Glue the pipe to hull. Then insert antenna fill pipe with mineral oil. Then use a little goop to act as gasket seal for cap and around cable slot. There should make for a much cleaner set up . Plus by using just little goop on the around the cap . You should be able to remove the antenna at any time in the future.
Did the Dixie cup once so I know.
Another hint next time you need a new Depth sounder to make things simpler take a 100 bucks get yourself a humming bird and just take some goop and glue the puck antenna to the hull and your done.

 

[Ralph Johnstone]

Wow .............................

........................... you should have checked this site (under the SEARCH menu) first and saved yourself a lot of work.

Non-thruhull transducers are best and most easily installed using a small pool of bubble free silicone sealant on the hull interior. No conical cups, no mineral oil, no epoxy glue, just silicone sealant.

Initially, test with a re-sealable poly baggie filled with water and laid on the hull bottom for best location. Place the transducer on the baggie and you'll have a reading. If not, your hull may be cored OR you need a different (better) type of transducer.

As noted by onecoolair, the mineral oil will eventually attack the cup. Take it slow when you redo this project and the installation will go much easier.

 

[c and c 30]

........................... you should have checked this site (under the SEARCH menu) first and saved yourself a lot of work.

Non-thruhull transducers are best and most easily installed using a small pool of bubble free silicone sealant on the hull interior. No conical cups, no mineral oil, no epoxy glue, just silicone sealant.

Initially, test with a re-sealable poly baggie filled with water and laid on the hull bottom for best location. Place the transducer on the baggie and you'll have a reading. If not, your hull may be cored OR you need a different (better) type of transducer.

As noted by onecoolair, the mineral oil will eventually attack the cup. Take it slow when you redo this project and the installation will go much easier.

Tough crowd. You guys sure are smartypants!

Actually, I found vaseline to be a lot easier than a baggie for testing. I did both, and there was no competition on that one.

Regarding the hummingbird, the whole point is that it is not a 4 inch cutout like the data marine. It is smaller, requiring fiberglass work.

 

[c and c 30]

I was concerned to hear that one of you tried the cup and it was not stable with mineral oil. However, perhaps your cup it was a different material. Mine is polystyrene (6 for recycling). It is supposed to have excellent stability with mineral oil. Other sources agree than alkanes (that's what mineral oil is) are not a problem. For example check out :

http://k-mac-plastics.net/data sheets/polystryrene-chemical-resistance.htm

It has only been a month, but I will see next season.

 

[onecoolair]

I was concerned to hear that one of you tried the cup and it was not stable with mineral oil. However, perhaps your cup it was a different material. Mine is polystyrene (6 for recycling). It is supposed to have excellent stability with mineral oil. Other sources agree than alkanes (that's what mineral oil is) are not a problem. For example check out :

http://k-mac-plastics.net/data sheets/polystryrene-chemical-resistance.htm

It has only been a month, but I will see next season.

Trust me it was the same type plastic cup. It actually melted a bit as the glue setup. The plastic cup is not u.v. stable and is designed and manufactured to have a short life span.
I recommended the upvc or pvc pipe because of the type of antenna you have that is you have a thru-hull transducer that you were wanting to mount without drilling a hole in hull. Plus by mounting it the way I suggest you still have the ability to remove antenna from its thru hull fitting for replacement in case antenna were to fail or you were to for some reason need too add more mineral oil or spirits. If it were just the standard puck style antenna like humming bird uses. Then the only reason for using a very short piece of pvc pipe or a bottom less plastic gladware type container glued to hull would only be for containing the goop while you push the puck style antenna down into the goop against the hull. Whats great about the goop product over using epoxie is the goop will not damage the antenna. Plus if you ever had to remove or move the puck style antenna. All you would need is a spatula or putty knife to remove it from hull. Then just peel off the goop and remount the antenna in its new location.

 

[c and c 30]

Well, concerns about durability of hard polystyrene notwithstanding, the boat, AND THE PLASTIC CUP TRANSDUCER BOX, withstood Sandy, in the water, and still both work fine!

 

[c and c 30]

Still working after Sandy and the winter.

 

[Maine Sail]

Alternatively a toilet bowl wax ring formed to the hull with the transducer pushed into it can work for many years.

Personally I just use a P-79 style in-hull transducer kit...