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I thought my 1999 Cobia 204 center console boat had 100 gallon fuel tank?

R

rjw4259

Contributing Member
So believing I had a 10 gallon tank I put 2 cycle oil into the tank for 50 gallons. The tank had 6 gallons in it that I just bought from the gas dock where I'm moored. I know the tank was empty because I ran out of gas and my Yamaha 150hp 2 cycle stalled out, bought boat home with kicker motor. So I am basically concerned about 2 things.First at the pump the fuel tank was full spiting gas out of vent. There's too much 2 cycle oil in the tank. I figured out to be 4.33 oz per gallon. The question is how will my engine run with 1.7 oz's too much oil per gallon in the fuel? The second question is how is it that I have a 35 gallon fuel tank when all the specs I have read for a 1999 Cobia 204 lists fuel tank capacity 100 gallons??? I bought the boat used in 2008, Could the original owner have ordered with that small of a tank? I really couldn't find any answer at Cobia's website. Any way any help is appreciated!
 
A Yamaha 150 has oil injection. There is no reason for any oil to be added to the gasoline tank.

The motor will run but it might be prone to smoking excessively. Maybe fouling spark plugs. Carbon build up within the cylinders.

If you can get access to the fuel tank sender there might be a placard on the tank that provides the tank capacity.

Fuel spitting out of the vent is not always indicative of a full tank.
 
Thanks for the information. My boat either never had an oil injection system or it was removed by the previous owner. Today I was able to remove enough of the over treated fuel to add new fuel to bring the oil ratio down to about 2.7 oz per gallon. I will never, ever put 2 cycle oil in the tank before adding the fuel again. I have asked a Cobia rep about this and for that model of Cobia the fuel tank should be 100 gallon capacity! The big question is why won't my tank take more than 35 gallons if it is 100 gallons as they affirm, or given that what he said is true; a better question would be what could possibly be wrong with that tank? I'm just at a loss to explain this, Boscoe, thanks so much for your help!
Bob
 
Inspect the fuel fill hose to the tank and the vent hose from the tank. Either or both could have a restriction. 21 year old boat, might be time to replace both. And the tank sender. Get the best sender possible for not much money. www.centroidproducts.com
 
Thanks Boscoe, I got a couple other replies to this thread said about the same as you suggest here that I am running out of gas but not emptying the tank. I assume that any work done with the sender or the fuel pickup will require the tank to be drained, is that correct?I sent an email to the link you gave me to try to find out what components I will need and the cost for those. One of the replies mentioned an anti siphon , is that on the sender or the pickup tube? Thanks all for your help.
Bob
 
You do not have to drain tank. But you dont want it totally full.anti siphon is the fuel line barb attached to withdraw tube
 
Thanks Rwbutler, i took the access plate on the floor off, I can see a round thing with some wires on it, to the rear of that access hole I see a kind of square aluminum fitting with the fuel hose on it which goes to my fuel water separator. Is the anti siphon on that? If so that was supposed to be replaced by my boat mechanic last August? How do you get it out before I start trying to do it and break some expensive stuff? When I ran out of gas the fuel gauge was indicating empty, does that fuel pick up have anything to do with the gauge. Is the fuel gauge lying to me or is it the sender? Thank for the help.
Bob W
 
The round thing with wires is the fuel gauge sending unit.remove sending unit,poke a wooden stick down the hole till you hit bottom,pull stick out.is it wet?does it smell like gas?
The fuel hose is attached to a barb(may or maynot be a antisiphon valve))the barb is attached to the withdrawal tube.
Our goal is to see if tank is empty.
 
Guys, I got into the fuel tank access hole and took some pictures. I have attached 3 of the 4 I wanted you to see. I'm still trying to get the other one to upload. These photo's show the tank label with the size of the tank clearly identified for 100 gallons, there is a gauge on the sender, if you can see it there is a red arrow on the gauge pointing to F for full. I have another picture of the pickup tube I'm still trying to upload. I will try it on another reply.
 
Rwbutler,

Thanks for the reply, Took the Rochester sending unit out, measured 16 inch tank depth, fuel level was to 13 inches. I felt as far as my finger could reach along the fuel pickup tube I have about a six inch index finger so it does appear to be intact to the length I could reach. I measured the fuel tank top as 48" by 48", the depth is 16 inches. I can't see the bottom of the tank, my guess is that it is beveled on the bottom, because the tank is rated at 100 gallons, a 48"X 48"x 1.33 tank figures out to be 159 gallons so I believe it is beveled on the bottom.
I have tried to get the fuel pickup out but failed miserably, that thing is really in tight, will have to find a better wrench to get that thing loose. The anti-siphon valve was replaced last august. So that's where I stand with the problem. I am ordering a reed type sender, don't like the float arm type. I'm open to any other suggestions, could still be a pickup problem I guess.

Bob W
 
I just got this boat back after over 1300 bucks of engine repairs: carbs, fuel pumps, sparks, fuel lines, anti-siphon valve, fuel/water filter. The engine now runs fine on off plane. Had it up to 29mph the other day for a few minutes. I removed the fuel pickup and it was fine, few scratches but no breaks in it. I am ready to believe it didn't run out of fuel, but it sure looked like it did. Took several times pumping up the primer bulb till it finally started up. Its been running good since then, haven't used much more than 10 gallons, guess I'll know more when I get down about 35 gallons and it fails again? Thanks for all the help guys!
 
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