I am going to rewire my bass boat ( tidecraft wildfire 175 w/ 150 johnson) should i use regular wire or should i use marine grade wire? :-/

What do you mean by regular wire? Use marine grade or at least automotive grade. Automotive grade is designed to withstand alot of vibration, so it won't break easily. I'd say Marine grade also has some type of corrosion prevenative.

The wire you use should be stranded and have the individual strands tinned = look silvery, not like copper.  You should get wire with insulation rated for 105 degrees C to minimize the chance of melting if it gets overloaded and hot.

what i call normal wire is  MTW (machine tool wire)or THHN ( stranded 14 guage) would it work  as good as marine grade  which is stranded and tinned ?

Im in the process of rewiring my boat as well and Im using marine grade wire.

THHN is a stranded copper wire, but is designed to be used inside conduit in buildings. It's insulation is not designed to take the abuse a boat and the elements would give it. Automotive and marine wire has a more rubbery insulation and is treated to help it withstand the elements. I'm sure your looking at the cost issue, but in the long run it's just not worth using THHN. Mpst of the things on a boat lights, small pumps, ect should be OK on 14 or 16 gauge. The only thing that I can think of that will require anything heavier is the trolling motor. I've been an licensed electrician for almost 20 years and learned along time ago do it right the first time, and forget it. Good luck.