I have a 'Bud installed' 4 cyl 42hp Universal (Westerbeke) M-50B. Pretty honkin' big engine and I was able to maneuver my stb fuel tank out without cutting/disassembling anything other than the removal of the cockpit drain hoses. I did have to cut off the corner of the little fiberglass 'step' portside aft in the engine compartment to get the port tank out. I just fiberglassed it back in after I got the tanks steam cleaned and access panels installed.
So it can be done but it was definitely a 'Chinese puzzle', having to turn it this way, lift the forward end a bit up, turn it back the other way, slide it forward a bit, rotate it the other way, now slide back to original position (but on it's side), etc. etc. etc..
But the biggest challenge was remembering how they came out... but in reverse :)
As far as the water tanks go assuming a factory built boat that should be easy . Just lift the floor panels in the saloon 'unbuckle' and lift out the fwd tank. Remove the manifold, unbuckle the aft tank, slide it forward and voila!
Consider yourself lucky. I've watched owners of newer 'big buck' boats have to repair their leaky water tanks that were designed as *part of the hull* or black iron tanks so 'integrated' into the design that major sections of the cabin had to be cut out to even get to the tanks.
That is one aspect I feel is extremely desirable in the Westsail... there isn't hardly a place in the Westsail you cannot get access to (except the jib track & chainplate backing plates... arrrgh!).
