How to clean grady 190 gas tank – the hull truth – boating and fishing forum gas finder map

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Before I fire up my 2000 FICHT 200 on my 1987 Grady Tournment 190 project boat, I want to clean the gas tank incase it was bad gas that blew up the Suzuki that came on it. I read to remove the sending unit and that it had screws holding it in, I can’t find that. Either mine had the entire asssmbly that screws in with a big white maybe 2” bolt thing or I’m looking at the wrong part. I’m nervous to try to remove anything that it will break on a 30 year old boat. The gauge reads full, but I tried siphoning it and got nothing. I tried using the squeeze bulb to suck it out and got nothing. I tap on or shake the tank and it sounds empty. My idea is to put 5 gallons of gas in there with a ton of dry gas and then squeeze bulb that out, is that a good idea or is there another way? Does anyone have pictures or know how to get something open so I can shop vac out the tank?

I have a blue wire from the tank ground that wasn’t landed anywhere that I hooked to the battery ground and the tank still reads full. The pink wire is landed on the gauge but I couldn’t find it at the tank, perhaps it comes out of the sending unit and that’s why I can’t find a sending unit that has screws to remove it?

I’m not familiar with your set up, but on my Wellcraft, as would be the case with many boats, the fuel tank is under the deck floor and the various fittings/pipes etc. are accessed via two circular access plates in the floor. The gauge sender is on the top of the tank, screwed down with 6 screws. The pink wire you mention is the gauge sender wire, ie. it sends the signal from the tank to the gauge. If it isn’t connected, the circuit is open and not surprising that the gauge reads "full". It’s really only displaying a fully open circuit.

What is the tank made of? If it’s aluminium it should be grounded, usually by a wire bolted onto a small tab on the tank. Siphoning old fuel from the tank via the sender gauge opening is the usual way to go. I did this, using a primer bulb, with a section of thin pipe (old brake line) fitted into the hose, which allowed me to get down into the lowest point on the tank, where any water would sit. It’s heavier than petrol and will sit beneath the fuel. I tipped the trailer up on the jockey wheel to encourage any gunk/water to settle at the rear, lowest point. Using the thin pipe allows you more accuracy.

Ordinarily your fuel tank should have a large fuel fill hose going in, a smaller vent line coming out, a fuel feed to engine coming out and a fuel gauge sender, all of which would usually be mounted on the top of the tank. Guess you’ll have to have a poke around. Pics might help.

Hi. I have some experience with older Grady’s and pumping out fuel. If I were you, I’d follow your fuel delivery hose to where it connects to your primary on-board fuel filter fixture. I’d disconnect the feed hose and hook up the electric pump using a hose barb to hose barb connection, with appropriate band clamps to secure the hoses in place. This works, because your engine fuel pumps pull the fuel through the on-board filter and your tank dip tube should extend to just about 1/2" off the bottom of the main fuel tank.

After you carefully remove and dispose of the old fuel, fill about 10 gallons of fresh fuel into your tank and find some way to slosh it around. Driving the boat around on a trailer is a fair approach. Pump out that cleaning stock and install a new primary fuel filter. Keep spares on hand.

If you’re truly the anal sort or suspect that the tank is well and truly fouled, you can remove the tank hatch, cut out all of the foam holding your fuel tank in place and haul out the tank for a more vigorous cleaning process. Having gone this route myself, I usually do option A whenever possible.