1973 merury 850 will not idle

[Moody Blue]

Re: 1973 merury 850 will not idle

new lower unit oil turned milky after running for about 15 minutes and it had time to settle after running that I am pretty sure that it was not foam. How much water can be in it before I have to worry about it freezing and busting something? This should be under another thread but figured it would be an easy one. Boat is in the garage but not heated and very little insulation. I guess I can run it a little in neutral with milky oil a couple of times. I have got everything that says seal or o-ring in lower unit on order. I have already replaced impeller and all gaskets and upper housing.

Let the motor sit overnight and then remove the drain plug slowly. IF there is water in there, it will drain out first follwed by oil. If you don't see any water then you are good to go.

IF you had noticeable water after running for just 15 minutes on muffs, then I would guess that the lower waterpump/driveshaft seals and/or possibly the shift shaft seals are leaking. There are only 5 places water can enter the gearcase. 1) drain plug 2) vent plug 3) prop shaft seals 4) lower driveshaft (waterpump) seals 5) shift shaft bushing/seal. Since the gearcase is not underwater then you can rule out the "external" sources of leaks.

No predicting how much water is "safe" from freezing in the lower unit. If there is any concern, drain the oil.

 

[Maxz695]

Re: 1973 merury 850 will not idle

Drain it completely. Don,t risk expanding ice cracking the lower. True water will exit first by removing the lower darin plug alone as oil floats on water but, Some water may still be in the mix. I wouldnt chance it Leave the drain plug out over night and let it all weep it,s way out. we can figure the best course of action later. PS there will still be enough lubricant for a short test run when the weather clears. Get a(q sticks) quart of 90 weight Volvoline gear oil or the like to refill it and order a set of drain and vent plug gasket rings for now. As stated Prop seal could be bad O ring under the waterpump base and the seal could be bad as well as the shift shaft gasket could be bad. Just don,t risk it I,m from CT I lived through Nor Easters in a van with a sleeping bag to save my but. (Over 10 years) Waking up to see Ice condesation all over and my window washing bucket solid ice in the morning. Nothing like a hot cup of Dunking Doughnuts to start the day off driving in the mess. Better safe than sorry is my choice.

 

[Kmyers]

Re: 1973 merury 850 will not idle

Thanks guys, in draining until I get my seals

 

[Kmyers]

Re: 1973 merury 850 will not idle

Hey, I hope I give everyone a long break, I tried to get motor to idle again today on the muffs after resetting idle mixture screws to two turns out and still had no luck. As stated above rebuilt carbs, all new hoses rebuilt fuel pump except checks could not find any leaks had a little at primer bulb when I really pumped hard but I figured that is normal. It is new but I did pump it very hard.

 

[Maxz695]

Re: 1973 merury 850 will not idle

There should be no leaks period If the bulb is hard it should at least be getting some gas, spray some premix fuel with any cleaned out pump spary bottle to get it to start as it might not have enough fuel (A Dry condition). Choke the motor and icrease throttle until it want to fire then release the choke and it should fire up. If it dies after a few seconds then the carbs are not pushing fuel, and you need to have another look at the pump, and the lines, and the carbs to be sure there are filled with fuel. You can undo the brass fittings at the lower part of the float bowl to see if fuel is emptying out in which would indicate fuel pump is working. If the float bowls are full then you have blockage or the fuel level is too low. If over filled then the needles are not seating flooding the engine. Thanks your my 2000th post

 

[Kmyers]

Re: 1973 merury 850 will not idle

So if my floats are set to low will the motor only run at high rpm and need choke to reduce idle? I did open up the fuel pump again and checked the check valves they seem fine, diaphragm looked good. I know my floats are set pretty close to spec how much off can make it bad enough not to run.

 

[Maxz695]

Re: 1973 merury 850 will not idle

The bowls need to have enough fuel in them to be pulled in by the low speed jets. The Main jet takes over after the engine is runing and pulls fuel from the carb through the main jet with a filled bowl and sucks fuel as needed to accomidate throttle opening and fuel air flow. If the bowls are not to the prescribed level the fuel along with air get sucked in and not just the fuel it needs. Also a proper float level must be made for the bowl to have enough fuel. As the carbs use the fuel the float drops letting more fuel in. If the needles are stuck or close to soon there is not enough fuel to be pulled to keep the engine runing at a decent idol. The Float bowls should be full but not over full to the point of having any fuel in the Vent! If you see fuel in the Vent (Not the main jet) then the float is set to high. Readjust to have just a bit less raise of the float and properly seat the needle. It is imparitive to check the fittings leading into the carburetor for fuel line remanants as it will clog the port to the needle seats, Even a small ity bitty piece of fuel line partical that has come fromt he lines from erossion or corrosion or even ethenol must be removed or you will continue mto have the problem until it is removed. The intake port for the needles is very small and easily blocked. Any air entering the system will affect the pressure sending fuel to the float bowl. A total dismantle of the carburetor including all screws jets needles is recommended with a good soaking and compressed air to get as much if not all or any debris out of the ports for fuel flow. Hope this helped

 

[Kmyers]

Re: 1973 merury 850 will not idle

Thanks this does help and I'm sure it will help others also. If there air in the fuel lines and the bowls have filled and needles seated does the air have a way out until the floats go down and the air goes out the vent in bowl. I have a very long 3/8 fuel hose that changes to 5/16 at the quick disconnect. Will the fuel pump have any problem pulling all that fuel?

 

[Maxz695]

Re: 1973 merury 850 will not idle

I run 3/8th from the tank to the primer bulb then 5/16 to the quick disconnect then I use 1/4 from there to the fuel pump then I added an inline filter also 1/4 inch fuel line and then 1/4 from the filter to the carb fitting on #2 and 1/4 line from #2 to #1 top carb. By putting the filter between the primer bulb and the fuel pump is a NO NO as it hold air and resricts the fuel pump from having a small steady uninhibited source to pull through. it can push through air but it connot pull through air. Hope this helps. THE FUEL PUMP IS PRIMED BY THE BULB Once primed the line is full of fuel and no air. It has no problem pulling the fuel if the line is sealed. If air get in the system it,s easier to pull the air then fuel. This must be securely sealed to work properly. The vent on the carb lets air escape as fuel is coming in. The needles close the intake when the bowl is full before it overflows into the carb or out the escape jet. The level of the carb float lets the bowl fill withough letting fuel into the carb throats There should be no sign of fuel in the carb vent or the carb throat whatsoever when priming it.

 

[Kmyers]

Re: 1973 merury 850 will not idle

I do have the filter I added before my fuel pump, could this be my problem it is before my fuel pump on my other motor which is a 1973 Chrysler and it runs great is there a difference?

 

[Maxz695]

Re: 1973 merury 850 will not idle

Are you talking Chrysler car like my Chrysler 300 1967 440 (MY First Car?) or the Chrysler marine engine? I don,t think anything should be between the primer and the pump that could create an air potcket or leak thats about it. It should be a sleek slim unhibited distance for the fuel pump to pull through. I would readjust it. The problem may lie interior of the engine but exhausting any and all other options must first be looked into. The simple angle of the filter alone could create an air potcket on the Merc and a different angle on the Chrysler would not have It I would change that to. When priming th bulb it creates a vac and if any springy air potcket is there it will not be a solid vaccum and the pump will faulter

 

[Kmyers]

Re: 1973 merury 850 will not idle

It's a 70 hp Chrysler outboard. I guess the easiest thing to do would be bypass filter for now and I will shorten the hose and put it straight into another fuel can in case there is a problem with the tank internally

 

[Maxz695]

Re: 1973 merury 850 will not idle

Almost a good idea but if you have a lawnmowergas can and get some fuel and long fuel line (Least expensive for testing). Put the hose in the can hook it to the primer Then to the fuel pump. leave off the filter for testing and then try again you will know weather it is the delivery or the engine or carbs. That would be great. You Must bypass the quick disconect as well if you have one

 

[Kmyers]

Re: 1973 merury 850 will not idle

If the weather is good I will be trying again tomorrow. Have you ever tested with any kind of low pressure guage if so how should that be done

 

[Maxz695]

Re: 1973 merury 850 will not idle

A pressure gauge on the line seems to be a bit over kill. If after doing the above precribed proceedure fails then there is a good chance you have internal problems. less the carburetors. By eliminating everything but the basic componants that are working properly as tested to this point being a donnor tank a stright line to the (Supposedly good working) fuel pump then straight to the carburetor. It eliminates any and all other added componants. Pump the bulb it gets stiff. No gas out of the carb when doing this. Engine fires after choking. Engine runes after unchoking it. Engine idols after setiing timing and throttle as specified in the proceedure for linc and sync. and engine continues at a steady idol then things would need to be done for hi speed timing and throttling up. Basics first. If we don,t conquer the basics we cannot rule out the componants that affect the basics. Then move on to Machanical issues and failures.

 

[Kmyers]

Re: 1973 merury 850 will not idle

I finally got a chance to start my motor up again on muffs and have found if I back my idle mixture screws out about 4 full turns I can back my throttle down enough to shift into gear. It sounds like it is still idling a little high but it makes no noise at all when shifting into gear does that mean it is low idle enough, I don't have a tachometer.