Converting Diesel Tanks to Petrol

Gents, I am converting 20 year old 38 foot boat that had Diesel sterndrives[2x225hp]. I am now putting a transom bracket with outboards [2x300hp].

My Question is how do I flush or clean the two 500litre diesel tanks and make good for petrol? [they are aluminium I believe]
I intend to replace the lines but the tanks are built into the boat.

Appreciate any advice you may have.

 

Buy a can of garage floor cleaner. It is a petroleum distillate combined with a detergent that dissolves the tank sediment. Let it soak for a few hours, then use a pressure cleaner or a garden hose; sediment, cleaner and water form an emulsion that you can easily pump out with a bilge pump or flow-jet pump.

 

Thanks CDK - after that do I rinse it out with petrol?

 

I don't think that's necessary. But it is important that the tanks are completely dry before they are used. Drops of water on the bottom of an aluminum tank are incredibly corrosive.

In your location the sun and dry air will probably remove all traces of moisture within a day.