Please Help With Best Transom-Ducer Location on 2120

[Jersey Jim]

I realize most owners on here have factory thru-hull round transducers. I had the factory omit mine, since they would not put in my transducer of choice, a chirp model.

Are there any late model 2120 owners that have installed transom-mounted transducers that can show pics of the cleanest water area behind the boat? Would this most likely be directly aft of where the factory chose to place their thru-hull transducers? Or even if you can offer input based on your observation of your hull and knowledge of fluid dynamics. I don't want to have to drill holes twice! Please post pics.

Not sure if this has a bearing on turbulence, but running 200 hp 4-stroke. I want to get her in the water next week, but have epoxy to cure and sand prior to dealer being able to paint it. Thanks.

 

[sydngoose]

Im sure you've read this 8X, but the instructions are spot on: I can't help you with a photo as I had an Airmar B60-20 thru-hull transducer on my last 2120 SC located in the bilge compartment, Port side just lateral to the bilge pump mounting pad. The picture in these instructions are worth 1000 words.

http://static.garmincdn.com/pumac/SideV ... ion_EN.pdf

 

[shawnee83]

You can see in the 1st pic where mine was originally mounted which was over the strake. I purchased the boat with it there and I moved it during the process of mounting bigger tabs. This is exactly where you don't want to mount it. I'd have to pull my instructions up to verify but I think it stated that it should be at least 3" from a strake? The other 2 pics are after the move but it's hard to see with the light and my poor photos but if you zoom in on the pic you can see it. It seem to work well in this location.

 

[Jersey Jim]

Thanks for good pics and examples. Yes, that prior spot you show is directly behind a lifting strake, a big no no. Below is a poor pic of my hull. There is 22" of deadrise from the keel's flat, to the 2nd lifting strake just left of the trim tab. You can't see the 1st (lower) strake, as it stops forward by quite a few feet. I also don't want to cause prop cavitation by mounting too close to the keel. With side-scan that would be my first preference though.

So does it look like a good mounting position is just left of that lifting strake just left of the left edge of the trim tab, no closer than 3" from lifting strake? Just behind the right most trailer roller? What are everyone's thoughts on that?

....... trying to resize the pic to attach...... stand-by...

 

[shawnee83]

Yes, exactly. That is about where mine is now, or perhaps mine is a tad farther down towards the keel but only because my tab now goes past that strake by a couple of inches ish. As you don't have that issue, just left of the strake, but no farther than nescessary, is where I would mount it. That should put it far enough away from the prop wash area too. Good luck.

 

[Jersey Jim]

Here is a pic of the 1st lifting strake going up from the keel. It stops in front of the 2nd set of trailer rollers, behind the trailer rear most tire. I hope this is plenty of distance to the transom, for the water to "clean up" in time for the transducer. Do you think it's an optimum position to place the ducer between the 2nd strake and the lower 1st one as if the 1st strake continued completely aft?

 

[shawnee83]

Yes, I think it will be fine. Just double check your units instructions for the required distance from that strake. You will be in between the two strakes either way and that water is cleaned up by the time it gets to that part of the hull. By the way Jersey, what port do you run out of?

 

[Jersey Jim]

....... By the way Jersey, what port do you run out of?

Bree-Zee-Lee marina in Cape May.

 

[warthog5]

Right in the middle of those rollers.

 

[shawnee83]

Cape May is a beautiful place Jersey. I'm sure you have good fishing there. Megabyte is just across the river from you in Lewis. You will see him on CP.

Wart, that far down? I was thinking about right behind the upper roller or just an inch or so below that? Although, if I were to measure mine right now, your recommendation is probably exactly where mine is. If you look at my pic above with the ruler, I pulled it out 18" from the outside edge of the original tab mounting, which is still the outside edge on the new one, so I could see where the new tabs inside edge was going to terminate. When I mounted my transducer, I moved it away from that edge about 2" down. I'm actually heading down to Beaufort this afternoon for a fishing trip, I'll take a good pic of exactly where mine is mounted for reference. It has worked well for me in its current location although I was concerned when mounting it that I was going to be to close to the prop. Staying off the strake is definately key.

 

[Jersey Jim]

Right in the middle of those rollers.

..... I was thinking about right behind the upper roller or just an inch or so below that? ....Staying off the strake is definately key.

Thanks guys, I split the difference. If the keel-most strake went fully aft and was visible, you would see that I drilled right in the middle of the two. In the pic above, you can see the shorter "keel-most" strake somewhere in between the two rollers. I kept the ducer 6.5" equally from each strake.

Thanks sydngoose for getting some cabosil to me. I hope by also adding the micro balloons into the filler, that it won't weaken the screw tension. The other day I tested the Six10 product (supposedly 105/205/filler) on some test holes without any other filler other than what is supplied in the caulk-tube, and it was quite strong when cranking down screws. The micro balloons seem to make a lower density mix, but maybe the cabosil strengthens it up? I added the two fillers 50/50. Was definitely "peanut butter".

 

[Megabyte]

Epoxy job looks pretty clean.

 

[rwp48]

Nice job, properly done!

 

[shawnee83]

Look great. Sorry, was running against the clock to get to marina to fuel when I put in TH night so I didn't get pics. I'll do it Sunday when I pull out just for kicks. I think your placement is about where mine is and you should be good.

 

[Jersey Jim]

Thanks everyone for comments & advice. Too late to change things now. If I want to relocate transducer in the future, will cut a thick resin board of sorts, in the shape of my deadrise, drill the same 3-bolt pattern in it to secure it to boat, and tap threads in more optimum locations on the mounted board. She goes in on Tuesday morning for the first time!

 

[sydngoose]

That looks super clean, Jim. Nicely done. Those screws will never back out or move, and no water will be invading your hull either. That is the way it's suppose to be done. Pat yourself on the back! Yes, 50/50 cabosil, microballons has immense strength; microballons just aid your fairing/ sanding process… more pics once she is splashed!!

 

[Jersey Jim]

That looks super clean, Jim. Nicely done. Those screws will never back out or move, ....

Thanks. One observation though when trying different pilot hole sizes & testing torque before thread stripping on my test blocks, fast tightening of screws created a lot of friction heat on the screws. I estimate 160F or higher by the feel of it. I've learned on this board that hard to remove screws from epoxy is helped by heating the screw head with soldering iron or other heat source. This softens epoxy.

So my recomendation... crank the screws down slowly, with pauses in between to dissipate heat and not compromise threads, or possibly sealant like 4200 or similar will lube/cool the threads. This heat was from screws run in/out "dry".

 

[sydngoose]

Your over thinking the installation... Never heard of heat being a concern or problem...is it done? Post a pic

 

[Jersey Jim]

Just an update on the outcome... Tuesday morning August 30, after epoxy & bottom paint had dried, I mounted & positioned the transducer with painstaking precision just before splashing the new boat, hoping to not have to pull her and make adjustments. Well it paid off! It worked perfectly from the very first mile. It never lost bottom once, even at 40 mph, during the entire 100 miles I managed to squeeze in between the hurricane's bad weather. The spray shield add-on Garmin makes for their "torpedo" shaped scan transducers worked like a champ too. Not a bit of rooster tail spray at all and the outboard was safe & dry. Been having a blast charting & imaging wrecks with unbelievable detail. Now if the water clarity would just settle down so I could jump in and spear a few!

 

[shawnee83]

Congratulations Jersey. I thought you would be ok where you put it. Hope you get some good weather by the weekend.