lowrance transducers interchangable?

Wondering if current FF (Mark 4) transducer will work with elite 5 regular or hd. Pin out the same?
Might upgrade but doesn't come with.

It might work with the regular (non-dsi and non-hdi) versions of the Elite series. Check specs online to see if your Mark 4 is dual frequency (83/200kHz). I believe the transducer model you want is HST-WSU. It definitely won't work with a HDI or DSI unit though. 

The 2014 Elite series uses the larger, blue/grey transducer plug.  I am assuming the one you speak of is black with the transducer & power all-in-one.  That one will not work with the 2014 units.  The new 2014 units use CHIRP and/or HDI setups.  Pat is correct ... the older Elite 4 & 5 units use the black all-in-one transducer/power cable setup & does not work with the DSI units.

Bill