Get hold of Greg at GT fibreglass. Did a great job on the transom on my swiftcraft and was a lot cheaper than any others I spoke to. Don't have the number but just Google 

..Hope this helps

 Sounds like you bought a near new motor with a bit of fibreglass attached to it.

The Guardians are quite a good riding hull so pulling the deck up and replacing it may be worth the trouble if you are handy with tools etc but if you have to pay someone it may turn out an expensive exercise

I have the same..mine is a 5.7m with an old Johnno on it, I had a budget of 10k at the time and picked this at 6k as I liked the high sides and the bit of room up front.

My hull was flooded for some time before I found the actual bung at the bottom of the bilge tank leading to the hull, it had a floor crack near the steering wheel board plus a few holes from the old seat poles were the water entered during wash down and from dive gear etc....so I know the colour of the water you mention...Tannin!

Its from the wood floor, the internal bulkies are glassed both sides to the top as I found out after putting a few inspection covers in my floor ....my floor still feels ok even with my 100kg bouncing around.....I've had it fully loaded with 3 blokes and 6 dive bottles in some rough chop and its still going strong.

Get a price for the transom, minimum get it checked once a year or repair if you can....Mine is beaten to shit but I love it :)....I'ts all I can afford atm so I fix it as I go!

If I can do it then so can you . If you can use a pair of scissors , a fin roller , a paintbrush , a jigsaw and a grinder you can successfully rebuild your boat from scratch . Using epoxy resins , biaxial matting and marine ply correctly will have you a bullet proof vessel that will make you smile from ear to ear as your pounding the crap out of it in shitty conditions. Look at what you've bought as an Investment in your boating future ! . There's a guy on YouTube called Andy , he's got a channel called boat works today. Start watching and learning .

 I am sure If you get to the stage of floor work etc you could get some foam floatation in there too mate , cause most of those older boats 

 have none and I get nervous when I hear about another older glass boat gone missing.

 Not scaring but informing , so you know to take advantage of adding any safety factor you can , and in the mean time before you spens another cent on the tub 

 grab a wearable inflating lifejacket and cable tie a P.L.B  too it .Good luck, theres thousands of older boats out there catching fish safely every year. 

 I got that foam stuff myself for t hat reason . Safety . Also got done at G T fiberglass when i got the transome done

 Good Hull. I would suggest getting the arse done professionally and do the deck yourself and fill it with Foam and you will be sorted for 10-15 years.