NEED HELP ON DECK MODIFICATION for ACCESS

Just got a nice center console 20 1/2ft. with a bad motor.
For the next 6 months I will be redoing the hull .... prepping it for a repower as I am stashing monthly for this,.....

Already straightened the mess down in the bilge and have now nice dual bilge pumps with new wiring....removed an old wooden seat in front of the console and also removed a livewell and 1 fishwell so it is physically and humanly possible to work and reroute things below deck........Brought the hull weight down from 2300 to 2000lbs so far without sacrificing any structure change.....

Now ran into a problem as I need to remove the old gas tank which is 82 gal and somewhat rusted as it is always wet underneath.....will install a smaller 44 gal as I am getting a 4 stroke......with good gas GPH......

The question/problem is what should I do to remove this gas tank ? It is huge and underneath the captains chairs with no access .
Do I need to cut the deck ..remove and install new deck panels or inspection panels for this .....???.

 

One way to start thinking about this problem is to answer the question of how the new tank is going to be installed. In other words, if the old tank was magically removed what kind of access path would be required to install the new tank?

If the new tank can go in without major alterations I would begin thinking about cutting up the old to remove, or at least limiting your cuts to just that required to install the new. Purging old tank and all appropriate cautions required of course.

 

I like bntii's idea of only cutting enough to get the new tank in. You'll probably have to beef up the rim of the cockpit sole around the cut, before you put it back together.
Make sure you purge all liquid and gasoline vapour from the old tank before doing any sort of cutting in that area.
Many builders do this kind of thing with the gas tank, building it in in such a way that it's impossible to access. I know it can be done safely and to code, but it's still irritating. I'd much prefer an access port big enough to lift the tank out; it can be screwed down permanently but I wouldn't glue/glass it in. You'll still need to mount fittings, sender unit, etc. and it's nice to be able to get at these if they break in future.

 

Yes...Thanks for ideas......
Here is a little more info I found out this weekend....the old tank is mounted in the center of the boat right under the captains chairs.......It is an 82 gal alum. tank and surrounded by rotting Alaskan Yellow Cedar which was used for the stringers encased in glass.......The floorboards under the captains chairs are rotten so I pulled the chairs out and need to yank the tank and put a new floor in and will then install a leaning post when done......

The new tank is a 55 gal Todd Tank Polyethylene lightweight from West Marine and is 51" long...25" wide and 16 " high...half the size of the monster tank in there now........I could put a rectangular access panel behind the captain chair area and slide this thinner tank in OK it looks like.......
The real problem lies in romoving the old tank.......as the bad part of the floor under the captains chairs is only abour 3 ft x3 ft.......and like you suggested is to cut the smallest amount of deck space is the way to go......So you are tellilng me the old tank has to be cut up to remove in different sections ?
Dangerous ?

 

With gasoline yes- at all times caution and deliberation should be used.

If you take a cut wheel to the tank with fumes inside you will be dead.

I would drain completely and open all access points. Let it air out for a few days then rinse the hell out of it with soapy water. Fill to overflowing several times as you go to make sure there is no fuel trapped behind a baffle. Keep going till the tank has absolutely no fumes. Use a metal blade on your saw's all and clip into sections.

Many here have more experience in this area and can provide better advice on how to defume the tank but this is what I would do.

Also- not really saying that cutting up is the way to go so much as one thing to think about as you work to arrive at the best solution for this task.