Cleaning/flushing a poly fuel tank ?

[eastbayandy]

My new to me  96 Striper 165 appears to have a plastic tank. I'm going through the carbs now and plan to fire up the engine using an aux tank. Is there a way to clean and flush the tank under the deck without removing it? The boat has been sitting outside since at least 2005 unused. Other than dried fuel in the float bowls, the carbs look in good shape.

[CTsalt12]

It can be done, I have used this method with success. 
1. Prime the fuel supply line, and get gas draining into your container.  To do this, the container you're draining into must be below the source tank.  So if your boat is on a trailer and container is on the ground, you should be okay.  Drain as much as you can via that  method. 
2. Once that's done, there will still be gas below where the fuel pickup can reach.  If you have access via the deck to fill/vent lines, you can stick a hand transfer pump in the fuel fill neck.  Get the pump to the lowest inner reccesses of the tank, and get as much out as you can. 
3. From there, add some Quiksilver Quickleen, a hefty amount.  Don't fill the tank all the way up with fresh gas just yet.  Start with smaller amounts, say a 1/3rd of the tank or less. 
4. Monitor your water/fuel separator very frequently.  You will get a few rounds of bad gas in that filter, dump and replace with clean gas. 

Good luck.

[eastbayandy]

THANKS Mr Salt