pressurized gas tank for 25hp Johnson???

[Pony]

I posted earlier in the week about some fuel that must be leaking from my carberator and pooling inside the cowl.<br /> <br /><br />I was planning on replacing the fuel hose from the tank to the motor today as the clip near the motor doesnt clip correctly all the time (faulty spring). I then was considering a tank replacement, as i want to run seafoam in the gas from time to time but am afraid to incase i loosen up something from the inside of the metal tank i have. So I want to go with plastic...Now its then that I start to question things. This is a 1987 Johnson and i assumed that this thing used a vented tank. I cant find a vent, and when i open the tank to fill it, it releases a lot of pressure. Is this tank supposed to be vented??? and is this pressure build-up perhaps the reason gas "leaks" out of the carb when not running???

 

[Walker]

Re: pressurized gas tank for 25hp Johnson???

Is this tank supposed to be vented??? and is this pressure build-up perhaps the reason gas "leaks" out of the carb when not running???

Yes and Yes<br />But a bad needle seat will be part of the culprit

 

[Goodoleboy]

Re: pressurized gas tank for 25hp Johnson???

Yes it sure an be the reason why. If you had really good needle and seats it would just about burst a hose before the carbs would leak.<br /><br />But yes all fuel tanks have to be vented Otherwise the engine would pull a vacume and you would be dead in the water for lack of fuel.<br /><br />If your tank dosent have the little krnuled valve head on the filler cap then its the type that vents automaticley flat on top. But its stoped up tight.<br /><br /> Get uh new cap. either kind dont matter much they both have to work tho. The one with the little krnuled valve on top you have to remember it every time you go out with your boat to open it up.<br /><br />I wouldnt worry about the fuel tank losening up some crud because you are useing seafoam once in a while. Your fuel filter will grab onto what ever comes out of it.<br /><br />If your really conserned about it then put one of the big clear plastic automotive/lawnmower/tractor filters in your fuel line. just a few inches after your primer bulb. Clamp that sucker up good and tight and your all set.<br /><br />More power to ya!

 

[Pony]

Re: pressurized gas tank for 25hp Johnson???

Is it odd that the motor would run so well if the tank wasn't vented properly??? This thing runs flawlessly.

 

[Chinewalker]

Re: pressurized gas tank for 25hp Johnson???

The tank is fine - the pressure you're relieving is gas expansion build-up - perfectly normal. The vents on those tanks are through a check valve that only allows air IN, not out. Don't want gas vapors escaping, and if vapors can get out, so can liquid gas. If there was a problem with your tank not venting it would suck are IN, not OUT when you released the cap...<br /><br />It's not a bad thing to occasionally relieve the pressure in the tank, particularly if it is exposed to the hot sun on a summer's day. <br /><br />Your problem is more one of the carb float needle needing to be replaced - not a problem with the gas tank...<br /><br />- Scott

 

[Pony]

Re: pressurized gas tank for 25hp Johnson???

Thank you very very much scott....that makes a lot of sense. I knew it had to be something along those lines, just because if it ran so well i new it couldnt be a vacumm lock or anything. So thank you again.<br /><br />Now about the float needle/seat.....Is this something that you guys would take of now, or can i wait till after the boating season to rebuild the carbs?

 

[Johnnielund]

Re: pressurized gas tank for 25hp Johnson???

Hi Pony 85. <br />I have a 1990 30 HP Johnson, with the same problem. More so if I tilt the motor up than if it's left down. Needle was replaced, primer housing has been replaced, all new hoses and clamps under the cowling. I spoke to a tech at Bombardier, and he told me that since the carb throat is open by design that was the nature of this motor. I assume he knows what he's talking about.

 

[Pony]

Re: pressurized gas tank for 25hp Johnson???

Scott or anyone for that matter- I just rechecked today and the tank let out quite of bit of pressure....I guess im wondering just how much pressure release is normal, as i suppose i still may have a somewhat faulty valve on the tank cover. Im beginging to wonder if thats why the hose fittitings dont want to fit quite right...like the pressure damaged them enough to act as vents if that makes sense??? <br /><br />I still have concern over this gas tank thing, even though the motor runs like a champ. <br /><br /><br />Johnnie- that bit of info is quite intrigueing....my motor is never down so i have nothing to compare it to, but this is how it sits when on the side of the house and whil being trailored to and from lakes. Let me know what you think.<br /><br /> <br /> <br /><br />BTW- just click on my images for a blow up, and I just noticed my tank shows up well, maybe you guys can give me some more insight on that cap.<br /><br />Oh and thanks for all the help guys, hope im not a pest....just want to keep this boat healthy and runnin so i can fish with my old man

 

[Chinewalker]

Re: pressurized gas tank for 25hp Johnson???

Hi Pony,<br /> As I said earlier - there's absolutley nothing wrong with your tank. The vent is NOT in the cap - it's in the fuel fitting on the top of the tank. If you look closely you'll see a couple of small pins in the mating face of the connector. Those pins are depressed when the hose connector is hooked up, and will allow air in as needed. When not hooked up the tank is essentially sealed. The pressure build-up is normal... Can be moreso if it's out in the sun. If you're not using it, unplug the fuel line from the motor to prevent the pressure from causing blow-by in the fuel system....<br /><br />- Scott

 

[Pony]

Re: pressurized gas tank for 25hp Johnson???

Thanks scott,<br />After a closer inspection i now see what you are talking about. I misinterpreted your post earlier and thought you meant that the check valve was somehow incorporated into the cap. Sorry for the confussion. I will take yout advice and disconnect the fuel hose when not using the motor. Thanks for the advice and for your patience.<br /><br />Now I can eliminate the tank as culprit. Still a litte stuck on the needls/seats. Scott you had said they are prolly the problem but I know johnnie said earlier that Bombadier had told him these motors are just like this, with the fuel leaking out of the carbs when tilted. Is this true?? and if it is or not should I look into rebuilding the carbs soon incase the needles/seats are bad??<br /><br />Thanks again for all the help guys. it is much appreciated.

 

[Chinewalker]

Re: pressurized gas tank for 25hp Johnson???

Hi Pony,<br /> Yes, fuel can leak out when the motor it tilted - ALL the way up, that is. Tilted up the carb may be at a 45-degree angle to the horizontal and the float simply won't float correctly at that angle. A little bit of an angle on the motor should not cause the carb to leak. By "little bit" I mean anything within the motor's normal trim angle range, and then some.<br /><br />- Scott

 

[Pony]

Re: pressurized gas tank for 25hp Johnson???

Hi Scott,<br />Thanks for the helpful information. I think after this boating season I will pull the carb off when i take the motor off to store it in the basement and put a rebuilt kit in it. better to be safe than sorry.