PLEASE HELP!! 7.5 HP Mercury OB starting problem

[Danny Bass]

Can someone please help me? I have a 7.5 Mercury OB motor that will not start. I bought this motor 3 weeks ago and it ran great, except for a little lag in the acceleration of the motor. Guy said all it would need was a tune up!!! I'm no mechanic but I decided to do the tune up myself and went ahead and changed all the plugs. When I took it out to the lake last time I pulled for nearly an hour and nothing!!!! Finally a huge blister later I got the motor started. Drove for about 15 minutes to my fishing spot, and shut it off. After fishing for a few hours, the motor would not start again, and has yet to start since. Any idea's or advise would be greatly appreciated.

 

[bigbadplad]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

Your motor should have a kill switch, I would try bypassing the switch if you dont have a multimeter to check the switch continuity

 

[Jis4Jeep]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

I've got the same motor 1984 and I'm not saying I have a problem as bad as yours but I feel your pain. I took it out last week started on first pull shut it off and then there's a routine for me. Pump gas several times pull the choke all the way closed pull ten times open the choke pull three more times before it starts. I wore my right hand out with blisters between my fingers and just pain.

Seems like she doesn't like to start right up after been off don't know why but I took it out today and maybe pulled 5 times the most during one stop. Check your plugs see if they are fouled. I haven't had the time to dig into my motor other then changing impeller.

 

[Danny Bass]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

Thanks bigdadplad. The continuity is good in the kill switch. I can get it started for about 3 seconds by manually giving gas to the plugs. Any other ideas?

 

[Dave1027]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

My guess would be a fuel system problem. Maybe a plugged fuel filter?

 

[Mi duckdown]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

Basics. spark and fuel.
Have you checked for spark. Yes. than go to fuel.
Just because it ran last time out means nothing.
Since you mentioned giving fuel, And hope it is not (starting fluid), you have a fuel issue.

 

[Jis4Jeep]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

Hmmm can you please explain why starter fluid is a no no!

 

[bigbadplad]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

you should inspect all of your fuel lines, sometimes they can visually look good, but the inside of the hose can be collapsed or collapsing as the fuel pressure creates a negative pressure inside the hose(ie sucktion)

 

[Mi duckdown]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

Starting fluid has NO lubrication. 2 strokes are based on fuel/oil consumption.
Using starting fluid will shorten the life of a 2 stroke.

 

[bigbadplad]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

stareting fluid(either) or "a can of sniff" in my industry as its known. If you really wanna see some cool stuff, by all means spray a little in the carb you'll get to see some really clean parts flying across the garage.

 

[Mi duckdown]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

Clean and Rebuild/the carb and pump. about 60 bucks.
make sure you have a clean fuel tank/hose/primer bulb with fresh gas absent of water. been there done that. Rookie mistake

 

[SC1650]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

These 7.5's are a little hard starting anyway. I went through mine doing all the stuff mentioned. New fuel line with bulb, cleaned tank, changed plugs, rebuilt carb, cleaned all lines, checked kill switch (had to rebuild it) and checked spark. Took it to the lake and first time I started it I pulled the rope about 15 times. Started and ran fine. Next time I took to the lake I had the same effort in getting it started. Pulled about 15 times before it would run. Once it is run for the day it will start after about 3 or 4 pulls. If cold and sat for any period of time, still takes about 15 pulls.

 

[Danny Bass]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

Clean and Rebuild/the carb and pump. about 60 bucks.
make sure you have a clean fuel tank/hose/primer bulb with fresh gas absent of water. been there done that. Rookie mistake

where do i find the carb rebuild kit for this model

 

[Danny Bass]

Re: PLEASE HELP!! 7.5 HP Mercury OB starting problem

I've got the same motor 1984 and I'm not saying I have a problem as bad as yours but I feel your pain. I took it out last week started on first pull shut it off and then there's a routine for me. Pump gas several times pull the choke all the way closed pull ten times open the choke pull three more times before it starts. I wore my right hand out with blisters between my fingers and just pain.

Seems like she doesn't like to start right up after been off don't know why but I took it out today and maybe pulled 5 times the most during one stop. Check your plugs see if they are fouled. I haven't had the time to dig into my motor other then changing impeller.

im having hard time finding this carb, kit do you where?