1984 Mariner 75hp fuel problem

J

jdollar5

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Aug 29, 2011
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Engine not getting fuel. Replaced fuel pump gaskets and diaphram (triangle type pump) and motor ran well. Same problem this week will not run unless bulb is pumped every couple of minutes. Bulb and gas line have been replaced. Blew air down into the tank, could hear it bubble so no restrictions there. Has anyone seen this problem before?
 
Z

zalmaflash

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Jul 15, 2011
Messages
7
Re: 1984 Mariner 75hp fuel problem

Mine will do the same thing if I forget to open the vent on the tank.
 
J

jdollar5

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Aug 29, 2011
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Re: 1984 Mariner 75hp fuel problem

I have a built-in tank with a deck mounted filler and vent. I will check that vent but I do not think it is plugged. Thanks for the reply.
 
S

Sunfish12

Petty Officer 1st Class
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Feb 6, 2011
Messages
260
Re: 1984 Mariner 75hp fuel problem

Disconnect the hose that goes to the carbs and while cranking see if you have a nice stream of fuel. If not you maybe losing vacuum to the fuel pump or something happened to the carb rebuild.
 
J

jdollar5

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Re: 1984 Mariner 75hp fuel problem

I have not touched the carbs but with the carb line unhooked I did not get much fuel through. I have put in new gaskets and neoprene diaphram that comes in the rebuild kit for the fuel pump. Not to much to that pump other than that and a couple of check valves. I replaced the gaskets under the check valves as they were included in the kit. Where would I be losing vacuum? Thanks for your reply.
 
S

Sunfish12

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Feb 6, 2011
Messages
260
Re: 1984 Mariner 75hp fuel problem

The fuel pump gets vacuum from the block. I'm not sure on your engine, the fuel pump is either bolted flat against the block over the vacuum hole or it has a hose from the pump to the block.
 
J

jdollar5

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Re: 1984 Mariner 75hp fuel problem

My pump is bolted directly to the block. No hoses for vacuum or other moving parts that I can see. I am assuming that engine vacuum from one of the 2 openings I see in there, pulses the neoprene diaphram, to pump the fuel through. Where could I be losing vacuum? I believe it is this pump that is the problem but have replaced the parts and if will run for short periods of time between pumping of the bulb to keep it going, as mentioned before. Thank you for you prompt replies.
 
J

jdollar5

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Aug 29, 2011
Messages
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Re: 1984 Mariner 75hp fuel problem

Thank you all who replied for your help. I have discovered the problem with the help of my son. He found gunk in one of the check valves when he noticed that one of them would move and the other was stuck tight shut. Took it apart and stretched out the spring a little cleaned it and reassembled. Engine runs like new now. Thanks again to all and hope this helps others. I was told at a dealer that those things never give any problem.
 
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