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extra fuel tank

eggharborrick

Contributing Member
85 silverton,twin 270 crusaders,twin 175 gallon aluminum fuel tanks. first question: the boat sat for 4 years with 3/4 tanks of fuel. needless to say we pumped the tanks of rank smelling fuel.the pickup tubes were covered in a varnishey green/brown slime. i'm assuming the inside of the tanks are the same way. it appears the boat was built around the tanks and they are not easily removed without cutting and extensive fiberglass work. is there any effective way to clean them? second question: if i place a 3rd new fuel tank between the other 2 under the cockpit floor, a smaller tank which will fit in the center hatch hole. i know i will have to vent it out like the other 2 but can i fill it in the hatch or do i have to run a fill hose out to the side like the other 2 also?? I'm not really concerned with a large fuel capacity as we only run up the river and a little out in the bay. i have the room between the other 2 tanks for about a 50 gallon 3rd tank. thanks
 
ALL tanks must be grounded and vented properly. The present ones--and the entire fuel system--will need cleaning or you'll be miserable. You might have to hire someone with tank polishing equipment to get it done right.

I like the 3rd tank idea, but it needs to be installed properly both for safety and operation.

Jeff
 
I too had been researching this addition of an extra tank. Understandably, proper installation is strapped down or lag bolted in place, vented, grounded and a separate filler neck.
After trying to figure out a feed to the tank or engines, I gave up........45-50 miles out and 45-50 miles in....with another 40-45 left for reserve is all I'll ever see.
 
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The fill must be on the exterior of the hull.....just imagine if the kid on the dock was checking out the bikini in the boat trying to tie up to the other end of the fuel dock when you new tank capacity was reached.....

The other item to consider before adding the tank is the extra weight you get to drag around.
 
i'm not worried about the wieght of the 3rd tank as i will not be using the original 2 tanks unless i can find someone or somehow to clean them out at which time i would remove the 3rd tank. how do they go about cleaning the inside of the tanks? anyone know the appox fuel usage of 2 270 crusaders pushing a 35ft silverton on a nice calm day running slow around 1800-2000?? right now we piped in a 12 gallon topside tank mounted on the swim platform to get it around the marina. looks somewhat hillybillyish but it works.
 
I'll bet!

The tanks get cleaned with solvents that are pumped in, swirled around, then pumped out (several times if needed).

Jeff

PS: It's perfectly legal to put a couple of the largest outboard tanks you can find on (meaning above) the deck (lashed down) and run off them. You'd need AI CG approved hose to connect them to metal lines (soon as possible) that run to ther motors.
 
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marine fuel tank cleaning sounds like a very profitable business to start but i can imagine the permits and hoops to jump through to do it. what size filters (microns) should i be running to catch the residual crap out of the fuel tanks if i can't find anyone to clean them? i already have 2 factory filters in line but thought about placing a 3rd right at the tanks until we can run the crap out of them. i do have brand new mechanical fuel pumps on so i dont think a 3rd filter will affect the flow.
 
You need at least 30 micron filtration before the pump, and around 10 microns after it. If I had this problem, I'd rig up an electric pump at the tank, then add a bunch of large filters in parallel after the pump. Eventually you're gonna work all that crap out of there.

Jeff
 
I don't know where you are located but a friend of mine used an outfit that did something called fuel polishing. Very satisfied with the results. This was in Maine but there are other outfits out there. As for the old fuel, I got rid of the crap that was in my tanks through craigs list. Good luck and have a good weekend.
 
I took the "Jeff Approach" in 2003. I carried extra drums of fuel on board for a long trip. There was a liner in the drums that the gasoline dissolved/loosened. It ended up in my 125 gallon fuel tanks along with a good dose of water. I used a large (2 quart capacity) filter/fuel-water seperator with an electric pump to clean up the tanks. It took some time but the fuel is clean now. Before I did this I rebuilt 2 Rochester Quadrajets. Pretty expensive mistake. Lesson learned: don't use this type drum for storage of fuel.

Chuck Hanson
PhD from the University of Hard Knocks
 
What model Silverton? I have a 40C, a little bigger than Knuckle47's. With the engines out I'm pretty sure my tanks will go up enough to swing the bottoms out if the cleats are removed. Beats cutting fiberglass or lifting the topside. Heck, if the tanks are shot, have them cut out with a sawz-all and buy replacements that will go in through the hatch.

For cleaning, look for residential oil tank cleaning and flushing services. We had our in-ground fuel tank inspected and cleaned. They pumped out the fuel oil, used a borescope before cleaning to inspect the tank then used straight kerosene to clean it. First with a 90 degree spray nozzle then filled the tank and agitated it before pumping it out. Saved a whole lot of aggravation changing filters in the middle of the night. My guess is cleaning a boat tank would be similar. Might be more of a fire/liability than an in ground tank though.

I've been considering a bladder tank for the bow. I would only need the extra fuel for fishing offshore. Run out on the main tanks then top them off and stow the bladder.

Not much help if your tanks are shot though.
 
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