Gas vent knob open or closed? Or is it something big?

[surftrish]

New to o/b motors. I just had this engine rebuilt--'83 50hp Johnson--and am having other problems now. I've ran the boat with the little vent knob on the gas tank (portable) closed. It runs great for about 1-2 hours and then the engine starts jumping/jerking and then dies. The bulb loses pressure also. This has happened the last 4 week-ends in a row and i've been towed in every time. I had the fuel pump replaced last week and there is some water (not a lot) in the lower unit. could all of this be a problem of my own making by not having that little knob turned open or could it be something bigger? thanks.

 

[ob]

Re: Gas vent knob open or closed? Or is it something big?

The lower unit water is a different issue.Probably have a prop shaft seal leaking.Fuel pump could have been related to vent being closed for several runs and ruptured diaphragm,but ,oh well.Open vent change fuel pump, and drain and replace lower unit oil.I would remove prop and get good visual on prop shaft seal to determine whether that is where water is entering lower unit.Usually but not always there will be some oil accumulation around seal if it is the culprit.The other leak possibilities are the driveshaft seal under water pump or the shift rod seal.Both of those require removal of lower unit assy.Also insure drain and vent plugs are tight and sealing .I'm never that lucky.Oh yeah Surftrish, keep your tank vent open when running.

 

[Brew]

Re: Gas vent knob open or closed? Or is it something big?

To ensure your lower unit leak isn't coming from your fill/drain plugs, replace the gaskets on the plugs when you change the oil. If old gaskets are letting the water in, you will have fixed your oil problem for about a buck.<br /><br />Like OB said, always keep the gas tank vent open while running.<br /><br />Good Luck.