- This topic has 7 replies, 7 voices, and was last updated 4 years, 5 months ago by
.
-
I was lucky enough a few weeks ago to be given for free a Johnson QD-17 from a guy who knows I enjoy fixing up old outboards (even though I am a complete novice mechanic, everyone starts somewhere I guess). They guy who gave it to me showed me that it had great spark and compression, but said after getting it out of his barn after 30 years he was able to fire it up and run it for about a minute before it would die and that he didn’t want to mess with figuring out the tank or lines.
I have seen videos online of people converting these from a two line system to a single line with a fuel pump, but didn’t know if that was smart.
I also saw some video where it said these old pressurized tanks could be dangerous if you accidentally tipped the outboard up to clear weeds off the prop they would shoot gas through the carb?
Any thoughts?
Finally can you still find replacement floats, gaskets, and two line connector rebuild kits? I was thinking about just replacing everything.
Thanks for any advice!!
I agree, there is no need to convert that engine to single line tank and fuel pump. Your tank looks clean inside…A new diaphragm, a gasket, and some fuel line is all it will take… In order to convert your engine to single line, you will need a fuel pump, single line tank/hose, and a bypass cover with pump mounting boss’.
There is nothing wrong with the two line pressure tank system, it is not dangerous, there is a pressure relief valve in the tank to prevent excess pressure build up.
The top of your pressure tank is broken, although it will work OK that way, you just won’t be able to wrap the line up neatly. But, I would consider replacing it anyway, since it is apart already. Just be sure to get one from a 6 gallon tank, the pick up and indicator arms are shorter on the 4 gallon tanks….Although, you can probably just use those pieces from your current top on a replacement.1 user thanked author for this post.
Either repairs to the pressure tank system or conversion to a pump are viable. I think it depends on what you want to do with the motor. If you just want to run the motor you might convert it. On the other hand, the pressure tank system is part of the character of the motor so if you are after restoration/preservation you might want to keep it as is.
I suspect there are a couple of safety downsides to the pressure tanks. One, you mentioned, is that the system will retain pressure for a while, so if the motor is tipped without venting the tank fuel might flow into and out of the carb–because the float won’t be able to shut off the gas if tipped too much. The other is that leakage might dump gas vapor into the bilge of your boat. I don’t consider these deal-killers for pressure tanks, but something to be aware of.
1 user thanked author for this post.
Fact is, many/most non-pressure tanks will hold pressure. They are one-way vented so air can enter the tank but not flow out. This is because of laws that say the fuel system cannot emit fuel vapors. Now hold on, you guys, I’m very aware that some old tanks have two-way vents because they were made prior to the emission law or do not comply. I did say many/most. The point is that they can build pressure due to sun/heat/agitation,, etc. ANY tank can be dangerous if in defective condition. Especially true in the case of rotted hoses, etc. As far as exploding, well maybe if the bottom is rusted out or something. Relief valves take care of normal pressure situations.
The carb float on those old OMC twins is hinged at the aft end of the carb body,, so it hangs downward when the motor is tilted, thereby closing the inlet needle&seat.. If it floods when tilted, suspect the carb, or float setting, rather than the tank Can’t say that necessarily applies to some other motors..
1 user thanked author for this post.
Just my $.02 here. I have replaced fuel pumps on 4 different motors, but have yet to replace one pressure tank!
David Bartlett
Pine Tree Boating Club Chapter"I don't fully understand everything I know!"
1 user thanked author for this post.
At our resort we never had any problems with the twin line tanks except for customers forgetting to loosen the cap.The odd time one would leak threw the carb into the boat after coming back to a gassy boat they usualy remembered to lossen the cap.
WE had many single line tanks that would build pressure we always ran them cracked open.
In 49 years I do not recall one twin line tank failure except for worn connectors
I probably changed a couple dozen fuel pumps.When I was around 12 years old it took me awhile to figure out why the 9.5 johnson kept fouling the top plug bad fuel pump gasket I made a new one out of an old time rain suit.Good lesson learned1 user thanked author for this post.
- You must be logged in to reply to this topic.
