Sounders for both deep and shallow.

[OneWayTraffic]

I am building a 5.3m plywood cored glass/epoxy boat, and am at the stage of my build where I am starting to consider electronics. Being a New Zealander we have access to both ocean and lakes anywhere in the country.

For fishing, my time will be divided between

1. trout/landlocked salmon fishing in freshwater lakes in 5m-50m of water 5-10% of the time. These are mostly uncharted.

2. Fishing near shore of Motanau/Banks peninsula in North Canterbury looking for reefs and other structure in 10-50m of water. ~40%
https://wetmaps.co.nz/#12/-43.0578/173.1413

3. Fishing off Kaikoura where the water drops off to 700m or more only a few kilometres from shore. Mostly bottom fishing, though the tuna sometimes come within range of a midsize trailer boat. Fish are often caught in depths up to 300m depending on the target species. ~40%

4. Other fishing in various places around NZ. Think of a type of fishing: we have access to it, a day or two drive away. Game, freshwater, deep drop, softbait, trolling, straylining...

It's been difficult to find a sounder combo that fill my needs for a price I'm willing to pay. Budget would be about the equivalent of $2k USD, which is flexible up or down. I don't want to overcapitalize the boat, and nor do I want to end up buying twice because I saved a few dollars too much the first time.

I was thinking about a GP1871/1891 for fishing in 50m-300m paired with either a TM258/TM260 or a TM185M. I am not sure on the benefits of the chirp for this kind of fishing. It seems to me that a narrow cone is best for finding structure etc in deeper water.

For shallow water I am led to understand that the 1kW ducer would be both overkill, and not be sufficient for covering ground, due to the narrow cone. I'd like to consider another transducer for this but am not sure if Furuno have any way to connect two transducers to a single unit. The only unit anywhere near my price range that has dual channel sonar is the Lowrance HDS 7".

Question 1: Does anyone have any thoughts on the benefits of running two smaller screen units say two 7" vs one single bigger unit?

Question 2: If I get a second unit, is there a suitable Furuno combo for finding structure in water from 5 to 50m deep?

Question 3: Would it be worth while to buy a cheaper P66 or similar and swap them out? Is there a switch that would do this, or do I need to plug/unplug every time I go out?

Question 4: Would another brand such as Garmin or Lowrance suit better the shallow water use? I would prefer Furuno for the main unit, but sidescan would be nice. I'm not spending for the DFF3D unit plue TZ touch combo. I don't have a spare 10k NZD to spend.

 

[Magnetron]

Greetings from your cousins on the US West Coast!

Given the situation, you might have fun looking into a GP1971F/1871F and a flush-mount pre-tilted 600W B60 50/200 through-hull. They even make long stemmed versions for cored fb.

Hope this helps, :sail

-Maggy

 

[Quitsa]

Perhaps I can help a little as I have a wood epoxy hull (what we call cold-molded in the US) 13m Diesel sport fishing boat but I also have 5.5m small boat I use to fish close to home. I think with your budget, you will be quite constrained in options. On the small boat, I have a through hull tilted element B60 transducer that is 50/200Hz fixed frequency and 600W input. The sounder is the built-in sonar in a TZT 2 display, which is very similar to what is in a GP1871/1971. The larger boat has a pair of B175 low and high frequency CHIRP transducers using the 1 kW sonar in a TZT 3.

In water less than 50-75m, the high frequency on the B60 is very good for fishing. It has a wider beam than the B175H CHIRP sounder and shows somewhat less detail but really does a great job showing fish The primary difference in practice is the high frequency 1kW B175H in my bigger boat can read bottom at a depth of 150-175m, typically 50m or more deeper than the B60. The low frequency side of the B60 works fine out to 250m -- I have never tried beyond that. The low frequency on the B175L 1kW works down to 500m or more.

I think a B60 tilted element transducer will be the most economical choice for you and also has the benefit of allowing a very clean flush mount. I cannot emphasize enough the importance of choosing the best available mounting location. With the B60 tilted element, you can mount 20-30cm forward of he transom as close to the keel as your framing permits. This puts the transducer in the deepest part of the hull in water that should be relatively free of turbulence. Transom mounts are very hard to get right and I feel comfortable in saying can never really equal the performance at planing speed of a good flush through hull.

Based on US pricing, a GP1971F and B60 tilted element should stay in your budget and give you a good sounder and chartplotter. The B60 comes in two tilted element mount configurations of 12 and 20 degrees depending upon the deadrise angle of the bottom at the mounting location. Pick the one that is closest to your hull deadrise so the beam points directly down. With wood epoxy construction, you will need to prepare the hole and seal the wood. The builder of my boat went to the trouble of cutting out an area of wood larger than the transducer and creating a solid fibreglass/epoxy mounting area. You can get by with just very carefully digging away some of the exposed wood core after cutting the hole and filling with epoxy.

 

[OneWayTraffic]

Thanks all. I yesterday bought a 2018 Lowrance Elite Ti with a tripleshot transducer on Trademe (NZ's Ebay) for a good price. That takes care of fishing in 100m or less. I intend to match it with a GP1871f or GP1971f for deep drops for Grouper etc in over 200m water.
I assume that the TM260 is the best for this? The other option is the TM185M, or the B60, which might be struggling at that depth.