Does anyone know of a direct replacement for the dash board gauge with out having to replace the wiring or transducer in the hull?

That would completely depend on what depth finder you have now.
If its an older straight bottom, then it's not likely that there is a new direct replacement available

tt

I've posted on this before. You need to post a picture of which one you have, AND the connector shape on the back of it. Humminbird makes most of them, they just get rebranded. If you have the 2 1/4" gauge and the wire connector to the transducer that looks "barn" shaped, you can likely just replace the gauge or the transducer.

Its a Lowrance 3500 depth finder gauge

Yep, looks like one of the Humminbird rebranded ones. What does the connector look like? But do some digging. You may be able to find a NOS one still in the box.

Like this

Is the what you mean "barn" shaped?

So, THAT connector is specific to Lowrance, it appears. NOT a rebranded Humminbird.
But the first thing I would do is call Lowrance, and see if they can give you any good info.

You can also buy NOS bezels for the Lowrance 3500 on eBay. The ones available appear to be gold, but you could have them painted or recolored with vinyl.
This may be an option:
https://www.ebay.com/itm/40533792651...3ABFBM-NrQ15dl

Went down this road with my flat bottom Fountain and a Lowrence 3400. Turned into a project.

Need a new depth finder.