I'm helping out my old club pick out a new piece for their boat. They are fixed on Humminbird, either a Helix 5 with SI/DI/GPS or a Helix 7 with DI/GPS. Is the decrease in screen size worth the SI? Note that probably 70%, if not more of their fishing is shallow Illinois fishing. 

Front of the boat, or at the console.  I have a 5 SI and it's fine up close, but of I was standing and looking at a bow mounted install, I'd want the 7. DI is less useful in shallow than SI, and I'd always want the SI anyway.

1 hour ago, J Francho said:

Front of the boat, or at the console.  I have a 5 SI and it's fine up close, but of I was standing and looking at a bow mounted install, I'd want the 7. DI is less useful in shallow than SI, and I'd always want the SI anyway.

I agree.

Console most likely. So if they get the 5, they can pick up SI/DI/GPS for what they would save from not getting a 7. Now just to be clear (since it's always SI vs DI) Doesn't the Helix 5 SI GPS (.com/Products/HELIX-5-SI-GPS/) have both SI and DI? 

Yes it has both

Cool. Getting the Helix 5 then. Now I'm not entirely sure just from looking at the description online, but does the Helix series come with a transducer or a mount?

Might also want to tell them there is an upgraded transducer you can get for that unit and if you get it swapped when its new you save a good bit of money. I believe its called XHS 9 HDSI 180 T. This has better detail due to different imaging crystals. 

The unit comes with transducer and mount for unit along with all hardware needed

First off all there are nine Helix 5 models. The top of the line version is the Helix 5 SI GPS.

The Helix SI units do not have true Down Imaging generated from a Down Imaging transducer crystal. It creates the Down Imaging VIEW by software blending the two SI pulses and narrowing the data some.

The Imaging it has views for are Side Imaging ( both sides) Left or Right side SI, and Down Imaging. It also has dual beam traditional 2D sonar.

The Helix 5 SI GPS comes standard with the transom Compact SI transducer XNT 9 SI 180 T that is 4" long.

It will produce sharper images with the HDSI transducer transom model XHS 9 HDSI 180 T since that is 6" long. The longer SI crystals produce a thinner imaging pulse which produces sharper images. If you want that one, it can be exchanged through Humminbird Customer Service for about $85 more which includes shipping. PLUS you have to pay for shipping the Compact SI transducer to Humminbird. If they have the HDSI in stock, they will ship it to you AFTER they receive the Compact SI transducer. Do not open the transducer mount package.

The HDSI is tuned to work with both 455 kHz and 800 kHz Imaging that the larger units have, but it will not add 800 kHz to the Helix 5 SI GPS or the Helix 7 SI GPS. They have 455 kHz Imaging only.