Chartplotting is in the nice to have basket; I'm happy to use my phone or a tablet with Wetmaps or Navionics. What I really need is to find structure and fish. 

I'm also thinking about putting a tilted element thru hull in rather than the transom models. At this stage of the build drilling holes is not a big deal. 

 From what I've been told Furuno is pretty much unbeatable in basic 2D sonar, and reliable as heck. But I could be wrong; electronics is a fast moving field.

A Furuno will give much deeper with a 1KW (preferably the TM260 not TM258, it goes wat deeper). Again not chirp, if that matters. This was a proven combo for many years

owt, for 250-300m you will need at least 1kw transducer. TM260 are great. You will see bottom at 500m if setup properly but more importantly, you will see fish at 300m

Sidescan/ downvu will only reach 80m if you buy the best transducer.

Garmin units are very easy to use, simrad are also very popular but as soon as you need 1kw of power, unfortunately the price starts at $4k

If you try and use a 600w tranny at these depths, you will be very disappointed, especially usind standard transducer, 600w in chirp would work better but price start at $4k for total unit/ chart/ transducer

I can have some of what I want at 1-2k but not all. That's always the way isn't it? If it weren't for fishing off Kaikoura a regular Garmin unit would do it all. The bottom there drops off to 1000m a kilometre from shore down Goose bay way, but I don't actually know what the fishing is like. I just picked 300m as a rough estimate of how deep I'm likely to get a line. 

The charters I've been on stay in 100m more or less, catching perch and cod. I'll ask a few local skippers next time I'm up that way. I do know that a few trailer boat people basically used to fish blind. I do have the option of getting a basic shallow/medium depth unit and just accepting that marking fish in 300m will not happen. 

Sorry I can't find the old post, I've never had much joy in searching for old posts on this site.  It was probably about 12 months ago.

Nice, but a little more than I am hoping to pay? Bay marine have a Striker plus with the GT52 for under 1k, but not as capable. It looks like their pure fishfinders are 500W only. 

There are no strakes or protrusions underneath except the central skeg and side sprayrails. That will help either a thru or transom mount. 

Biggest reason to go transom are side view and price. 

If you own it for 10 years, it will pay itself back based on finding fish (thats finding, not catching, as thats up to you).

You can also go with US version of sliding leg to change its position depending on your speed (make sure it locks though as a transducer dragging on the road is not a great look - personal experince).

If you're prepared to lift the budget you gave of $2000 to $3500-4000 (it would be 7inch at that price), I would absolutely recommend the 1kw 175 thru hull, otherwise the TM.

One feature I would recommend is sonar history scroll back. It's awesome when you are sounding around, as you can scroll back to find the best bit of sign you went over, mark it and then go back to that spot.

With the Simrad/Lowrance (that's all I know about), you can have 175M and the 3in1 side/down scan transducers connected at once. 

Maybe consider looking on Trademe for a unit to help keep price down. I wouldn't recommend a 2nd hand transducer just in case it's been left on out of water and the performance has been degraded.

Alan