72 merc 110

[trx88]

this motor was a jewel of mine for two summers, and slowly it began coughing and cavitating upon startup, now it starts, burns the fuel in the bowl and dies if i dont squeeze the bulb alot...

ive rebuilt the fuel pump, or check valve..

any ideas?

 

[jerryjerry05]

Re: 72 merc 110

Do a compression test and then re-do the fuel pump.You sure the gasket behind the pump is good?
If the only way it runs is the squeezie then the pump isin't working right.It takes good compression and tight seals.gasket.J

 

[trx88]

Re: 72 merc 110

the pump does not mount to the powerhead its sort of external and its merely a check valve, the vacuum for it comes from a fitting and tube at the side of the powerhead, im not sure that its getting good vacuum and whats a good compression level?

 

[carholme]

Re: 72 merc 110

trx88;

In this link to the fuel pump:

http://www.crowleymarine.com/mercury-outboard/parts/458_60.cfm

fuel is coming in thru line 21 and out through line 22 if it is running with the bulb.

Presuming that the tank vent is open, the check valve is ok and the gaskets are installed correctly, vacuum should draw the fuel. If it is not, is there a blockage in the vacuum line 12 or a leak in it or the fittings 9 and 13?

Gerry

 

[trx88]

Re: 72 merc 110

i am going to seal up 9 and 13 and check for blockage, ive been told before that these motors can loose vacuum like this because of a case gasket leaking.. can anyone recommend a good thread sealant that will hold up to fuel?


thanks guys!!

 

[carholme]

Re: 72 merc 110

trx;

You shouldn't have to use any sealant on those threads but if you do, do not put any on the first few threads. Permatex thread sealant would be my choice if you have to do it.
With the age of the hose and suspect blockage or internal breakdown of the line, I would replace it while you have it off. Split the old one down the centre and see if it was collapsing or degrading.

Gerry

 

[trx88]

Re: 72 merc 110

i replaced the line, built the carburetor, new diaphragm in pump, you name it,

the check valve/fuel pump is not functioning properly or its got a vacuum leak or its not making vacuum with the downward stroke

im not sure everyhting on this guy is so simple i dont know how its not working

 

[carholme]

Re: 72 merc 110

trx;

Have you verified that you actually have vaccum at fitting 13?

Is your tank vent open?

Gerry