7.5 mercury firing on one cylinder

[fishinwithmercury32]

I have spark on one of the two cylinders on this 1972 merc. I've heard it might be the coil but which one? How do I get the other cylinder to spark? New to this stuff so I'm looking for any help I can get. SN# 3275803.

Thanks,

 

[sutor623]

Re: 7.5 mercury firing on one cylinder

I have spark on one of the two cylinders on this 1972 merc. I've heard it might be the coil but which one? How do I get the other cylinder to spark? New to this stuff so I'm looking for any help I can get. SN# 3275803.

Thanks,

I had a spark plug wire on my '77 4.5hp fail. How do the plugs look? Hold a plug up to the block and give it a crank. Does it spark? Try the other one also. Then at least you know which cylinder to point your finger at. Once you find that out we will head up the spark chain.

 

[fishinwithmercury32]

Re: 7.5 mercury firing on one cylinder

I had a spark plug wire on my '77 4.5hp fail. How do the plugs look? Hold a plug up to the block and give it a crank. Does it spark? Try the other one also. Then at least you know which cylinder to point your finger at. Once you find that out we will head up the spark chain.

The plug wires look great. Both of them look brand new. The top of the two cylinders, (one on top of the other) are getting fire. The bottom of the two are getting no fire.

Thanks,

 

[Laddies]

Re: 7.5 mercury firing on one cylinder

Swap the 2 input wires on the coils if the spark goes to the other cyl the box is bad if it stays the same the coil is bad

 

[sutor623]

Re: 7.5 mercury firing on one cylinder

The plug wires look great. Both of them look brand new. The top of the two cylinders, (one on top of the other) are getting fire. The bottom of the two are getting no fire.

Thanks,

And plugs look good? Check connections to the coils. Does this motor have a starter and stator?

 

[fishinwithmercury32]

Re: 7.5 mercury firing on one cylinder

Ok. So dumb me. I have spark on both plugs now. (Just a loose connection, thanks Pete.). Now that I have spark, i've pulled the crank a few times with fresh gas and a clean carburator. I choked it but im not getting it to turn over even a little. What am i missing now? Maybe the fuel pump?

Thanks,

 

[sutor623]

Re: 7.5 mercury firing on one cylinder

Ok. So dumb me. I have spark on both plugs now. (Just a loose connection, thanks Pete.). Now that I have spark, i've pulled the crank a few times with fresh gas and a clean carburator. I choked it but im not getting it to turn over even a little. What am i missing now? Maybe the fuel pump?

Thanks,

No prob. Pour a little fuel/oil mix in the carb and try her out. If she starts up then you have a fuel delivery issue.

 

[fishinwithmercury32]

Re: 7.5 mercury firing on one cylinder

ok. so i sprayed some gas mixture directly into the carb. It started up and ran for about a second, then shut off. I checked the fuel line. there is gas flowing to the right side of the filter but not through it to the other side. What next?

 

[fishinwithmercury32]

Re: 7.5 mercury firing on one cylinder

so i took the fuel pump apart and took some pictures. My question is...does the diaphram and the screen/filter look ok? Should the diaphram look that flexible or should it have more tension?

thanks,

 

[sutor623]

Re: 7.5 mercury firing on one cylinder

so i took the fuel pump apart and took some pictures. My question is...does the diaphram and the screen/filter look ok? Should the diaphram look that flexible or should it have more tension?

thanks,

View attachment 137464

Maybe you have a clogged filter. Generally, if the diaphragm doesnt have a puncture it will work. But how well, is another topic. I like to check my check valves (little round buttons) by blowing into them and making sure they pop out and back in. Might as well rebuild the fuel pump now that it is open. Pull the carb and let it soak to. Just do a rebuild on this sucker and KNOW that you wont have any issues this spring and summer. Better to spend the effort now than on the water with the pull rope and a cell phone.

 

[fishinwithmercury32]

Re: 7.5 mercury firing on one cylinder

i blew into them and got a popping sound. Would the hi/lo on the carb have any affect on the running of the motor after it has been cranked. I remember tightening/loosening the gold bolt on the carb that affected the fuel intake a while ago. Im not really sure if this is an appropriate question? Will just simply rebuilding the carb and the fuel pump keep it running?

Thanks,

 

[sutor623]

Re: 7.5 mercury firing on one cylinder

i blew into them and got a popping sound. Will just simply rebuilding the carb and the fuel pump keep it running?

Thanks,

Cool so the check valves are okay. And yes, "simply" rebuilding this carb and fuel pump will have this motor running in no time. You have confirmed that you have a fuel issue. Just check all hoses, primerbulb, and connections. I had to change the fuel lines that are in the motor cowling when I removed the 30 year old connections. You will probably want to order the fuel input line and change it out while you are in there.

 

[fishinwithmercury32]

Re: 7.5 mercury firing on one cylinder

Alright. I'll rebuild everything and get back to you soon. Thanks for all the help.

 

[sutor623]

Re: 7.5 mercury firing on one cylinder

Alright. I'll rebuild everything and get back to you soon. Thanks for all the help.

Yeah man, good luck! Remember, order that fuel hose. Youll be kickin yourself if you put everything together and that new found fuel pressure busts through that old line!

 

[fishinwithmercury32]

Re: 7.5 mercury firing on one cylinder

Ok...so i've put new gasket and valves on my carb and fuel pump. Im still getting the same result. It will run when i put gas/oil directly into the carb but it wont keep continous running. a connection? pump?. Im at a loss.

Thanks,

 

[fishinwithmercury32]

Re: 7.5 mercury firing on one cylinder

Update..Im not getting any flow THROUGH the carb. It is holding pressure on the bulb but it wont transfer from the pump. Also, when i take the hose off of the line to the carb and crank, i have no fuel coming out....Anybody?