75 Horse Mariner flooding

[starkyb]

I have a 1988 75 horse 3 cylinder that for the most part runs great. But sometimes for no obvious reason it will start running rough and dying than hard to start. What I notice is that gas will start leaking out at the same time it does this. Not sure but it sounds like a float that is getting stuck. Is there something else I should looking for? If it is how do I narrow it down and repair it?

 

[Chris1956]

Could be a float, or it could be the fuel pump diagram.

Normally a float will stick at cold start, and flood or not allow fuel into carb at that moment.

A leaking fuel pump diagram will cause motor to load up while idling. The motor will stumble on acceleration, but often achieves high RPM.

Is your motor doing any of these?

 

[starkyb]

It does stumble on acceleration but will run without hesitation at WOT. But when I slow down and put it idle is when it will choke out and die, and start leaking fuel.

 

[Chris1956]

Sounds like the fuel pump diagram. Fuel pump rebuild kits are cheap and easy to install.

 

[starkyb]

Just FYI will a damaged diaphragm allow too much gas to enter the carbs or not enough? When it has acted like that in the past I have disconnected the fuel line and started it and than it seemed to smooth out, causing me to think that too much fuel is getting in the carbs rather than too little. Just checking my theory.

 

[Faztbullet]

Just FYI will a damaged diaphragm allow too much gas to enter the carbs or not enough?

Fuel entering the carbs are controlled by the needle and float...fuel pump just supplies the pressure. Most likely the original fuel supply lines are degrading internally and shedding small particles causing float to stick.

 

[Chris1956]

If the fuel pump diagram has a hole in it, raw fuel will enter the crankcase, bypassing the carbs. This will cause the motor to flood at idle speed, and can cause it to run correctly at high speed, after it overcomes the flooding.

 

[starkyb]

Ok, is it more common to see leaking fuel from a stuck float or a bad fuel pump diaphragm.

 

[Faztbullet]

A hole in diaphragm will not cause carb/s to leak . Rarely see these diaphragm fail as so thick but when they do fail the engine suffers as raw fuel takes out cylinder.

 

[starkyb]

I would imagine that with the problem being more intermittent, that its probably a float that gets stuck sometimes and sometimes not. If it was a hole in the diaphragm it would leak all the time, right?

 

[Mark ofs]

I have a 1985 35hp 2-cyl. The fuel pump had a diaphragm that was over 13-years old. Had 2-small tears starting on 2-different edges and the surface was disintegrating. It did NOT cause flooding to the carb, however it did allow fuel to directly enter cylinder 1. Note that on this model the fuel pump is mounted to the back of the outboard (red circle on photo), not on the carb...if this helps....

 

[Faztbullet]

I would imagine that with the problem being more intermittent, that its probably a float that gets stuck sometimes and sometimes not. If it was a hole in the diaphragm it would leak all the time, right?

That is correct....

 

[starkyb]

What should be my next course of action and what should I be looking for as far as correcting the float issue?

 

[Faztbullet]

See post 6