86 Mercury 150HP idling issues

[luv2flycessna]

My 86 Mercury 150 hp has developed an idling issue. While idling either in gear or out it seems to surge and sometimes stall out. I took the hoses off that I guess are the bleed back hoses that come from the reed block and to me seems like alot of fuel is being pushed through them. I changed out the plugs because they were black and wet and had not been changed in a while and thought that is what was wrong but still doing the same.

Is this normal to have quite a bit of fuel going through these hoses?

Running open throttle she runs great but come back to idle and starts rough and surging up. any ideas?

Also my reverse is shot. Is it hard to rebuild these lower units?

[RickK]

Also my reverse is shot. Is it hard to rebuild these lower units?

I had just left the ramp yesterday in the 170 and about 2 miles into the trip I heard a "clink" and then felt a lot of vibration.  I could still idle around but didn't dare try to push it.  I idled to the east shore which blocked the SE winds and then used my trolling motor to limp back to the ramp.  I fished all the way back and caught about 2 dozen Specks - keeping a 17"er for dinner.
I took the boat directly to the shop and they called me later and told me that my lower unit was the problem - so I guess I'll find out how "hard" it is to repair them.

[bdtsr]

Were all the plugs black or one, two? Black means rich. A stuck needle will cause flooding at low speed. Those lines are to empty the crank case off excess fuel that buils up. Don't remember if they have check valves like OMC or not. Make sure the air box is not plugged (bee's nest or something). Make sure the choke is not sticking.

[gw204]

Have you ever rebuilt the fuel pump?  If not, you probably should.  Cost about $15 in parts (if memory serves) and takes about 30 minutes.

[luv2flycessna]

Were all the plugs black or one, two? Black means rich. A stuck needle will cause flooding at low speed. Those lines are to empty the crank case off excess fuel that buils up. Don't remember if they have check valves like OMC or not. Make sure the air box is not plugged (bee's nest or something). Make sure the choke is not sticking.

All the plugs were black and all were wet.

The fuel seemed to be coming from the carburetor side of the lines not from the cylinder head side. Is that the way it is supposed to be flowing. It seemed like a bit much to me. While the lines were disconnected from the cylinder head it seemed to idle better but had fuel soaking a rag that I had them spraying into.

Air box is not plugged clean as can be.

This motor has the electric choke that squirts the fuel in. (Forget what it is called at the moment)

Thanks for your help.

I am also trying to figure out if this motor is worth  fixing or if I would be better off looking for  good used motor?

[luv2flycessna]

Have you ever rebuilt the fuel pump?  If not, you probably should.  Cost about $15 in parts (if memory serves) and takes about 30 minutes.

No I have never rebuilt the fuel pump but if it may be the problem I will try it and see. Thanks

[bdtsr]

You have a primer system. If the primer solenoid is bad and allowing fuel to flow without the choke being used, that could be the problem. Pinch off one of the lines at the primer solenoid and see if it clears up.

42859A2 SOLENOID KIT $115 from an online dealer

[luv2flycessna]

You have a primer system. If the primer solenoid is bad and allowing fuel to flow without the choke being used, that could be the problem. Pinch off one of the lines at the primer solenoid and see if it clears up.

42859A2 SOLENOID KIT $115 from an online dealer

I had the Primer solenoid line disconnected and made no difference. That was my original thought but unfortunately that was not it. But thanks for the suggestion.

[gw204]

The fuel pump is a diaphram pump that runs off of pressure pulses in the crankcase.  If there is a tear or hole in the diaphram, the pump will dump fuel into the crankcase.

[luv2flycessna]

The fuel pump is a diaphram pump that runs off of pressure pulses in the crankcase.  If there is a tear or hole in the diaphram, the pump will dump fuel into the crankcase.

AHHHHH so that may be my problem. If this was happening which end would the fuel be coming out of though? would it be coming from the hose on the carb side or from the cylinder head ?  when I pull the vacuum hose off where it attaches to the cylinder head fuel comes out of the hose coming from the carb. At first a small amount comes out of the cylinder head port but stop's almost immediately but continues coming from the hose that is still attached to the carb.

Should I be able to actually see alot of fuel coming out of the end of the vacuum hose if everything was working ok? It just seem's to me alot of fuel out of a Vacuum hose, if it were a fuel line I would be thinking different.

Thanks again for any help I do not know much about these engines.

Can we post videos on here, maybe some night this week I can shoot a short video and post what it is doing.