losing prime

[02cliff]

I've got a 40 mercury and after it runs maybe five or ten minutes sometimes maybe less,the primer bulb will be soft not collapsed just soft and then you squeez the bulb three or four times and it's hard and runs greatfor a few minutes what could be causing this?

 

[tengals123]

Re: losing prime

fuel pumps, carbs..<br />cheers

 

[Silvertip]

Re: losing prime

The primer bulb does not remain firm after you start the engine. It gets firm because it initially fills the carbs. When the float closes the needle & seat in the carb, there is no where for the fuel to go -- hence a firm bulb. When you start the engine, the fuel pump now draws fuel through the fuel line. The bulb under normal operation will remain relatively soft because it is only 1/2 - 2/3 full depending on its position. This is not an indication of a problem.

 

[Clams Canino]

Re: losing prime

That is all true.... and not applicable to his particular problem.<br /><br />Add vacuum leak ahead of fuel pump to possible list. Fuel pump is most suspect though.<br /><br />-W

 

[02cliff]

Re: losing prime

I had a johnson before I got this boat and it had a plastic 6gallon gas tank with a solid plastic lid no vent that I was aware of.On this 40 mercury it has a metal tank with vented cap but the vent was closed could this have been the problem causing this thanks for all the help

 

[02cliff]

Re: losing prime

All the gas lines appear to be in good shape no dry rot or anything like that also I don't see any gas leaks anywhere.

 

[Elmer Fudge]

Re: losing prime

Originally posted by o2cliff:<br /> All the gas lines appear to be in good shape no dry rot or anything like that also I don't see any gas leaks anywhere.

The only other alternative now is the fuel pump, change out the diaphrams and check valves.

 

[02cliff]

Re: losing prime

good news I guess I'm just a dumb a$$ hillbilly from tennessee I got back out on the water this evening with the vent on the gas cap open duh ran perfect.Kind of felt a little stupid.But it was just one of those things I didn't know,this is the first mercury I have ever messed with my dad is a firm beleaver in johnson evenrude so I couldn't swallow enough pride to even tell him there was a problem with my little merc.lol