want bigger fuel tank
 

i'm rebuilding my 85v20 cc when i pull the old one will a 100 gallon tank fit?

Well, you gonna have it custom built or go with OEM stuff?
Here is some of the replacement ones.
http://www.moellermarine.com/afterma...rmanent_tanks/
and
http://www.moellermarine.com/oem/fuel_tanks/
At least you will have some dimensions to play with.

I have an 87. based on the information baki has provided I believe I could get a 90 gal tank into my boat. I would have to remove the bulkhead directly under the frount wall of the console that would give me 16" more room till I hit the next bulkhead. buy puting the tank in back first then sliding it foward i think it would go in without cutting up anything topside.
look at part # FT9002 and see if you think this will work for you.

How about the standard belly tank along with a pair of saddle tanks. Redundancy is a great thing. I loved the 20 gallon saddle tanks on my old V.

did you mount the saddle tanks right beside the belly tank?