HELP.. Mercury 850 (85 HP) Issues

[Chris1956]

Re: HELP.. Mercury 850 (85 HP) Issues

Clearly your motor need some carb help. Was it in a fire or did it overheat so badly to melt the venturies. The cowl looks to be a 1976/7, but I never saw air boxes like that.

I would take a look at the carbs especially the floats, inlet needles and seats. Also the venturies sit on top of the main fuel nozzle. Make sure they are not clogged by the melted plastic or dirt.

You might post a picture of the carbs w/o the airbox. maybe we can source some venturies for you.

 

[bktheking]

Re: HELP.. Mercury 850 (85 HP) Issues

I'm working on the same motor right now, those venturies are melted, what you need to confirm is the hole coming up through, it it still ok or melted over, pulling the carbs will tell you. Once you get the carb apart you can shove a nozzle up through the top of the venturies to confirm if the hole is still good(I used the red nozzle from a can of carb cleaner) If I were you I would clear out any melted plastic through the center hole (looking from the front) and call it good. My motor is a 76, look at your starter, it's stamped 76. You need to remove 4 bolts, they hold that air cover on (with the 6 holes) then 2 bolts per carb and the carb will come off, start with the top then remove the bottom, be careful not to break the platic link between the 2 carbs. Inspect the needles in the carb as well as the float, check the pilot jets for crud as well.


Pull the screw out of the fuel pump cover, it's to the left of the switch box. There is a screen underneath as well as an o-ring. Make sure the oring is not compressed and that the screen is clean. Merc dealers sell a rebuild kit that comes with the gaskets and diaphram and check valves for around $25, the diaphram could have hardened from sitting and just needs to be replaced.


These motors take surface gap plugs, I hope that's what you replaced the old ones with.

These motors are renowned for holes in the water jackets, you need to confirm before anything else that it isn't water intrusion into the cylinders, it wouldn't surprise me if that's the issue.

 

[jimmy120]

Re: HELP.. Mercury 850 (85 HP) Issues

In regards to your engine, did your engine work correctly if you pumped the fuel bulb? I think mine is fuel related cause when I pump my fuel bulb the engine gets up and goes, indicating to me it is fuel related. I found the stator part for $110.00, before I replace it I want to make sure I replace all the cheaper parts first.

Where is the water jacket located on the motor?

i swear it sounds like you have my motor in your boat. i had gas in the case surrounding my carbs also. when you give it the throttle try easing the shifter very slowly past the bogging down point. sometimes i could find the sweet spot and i would get full throttle. also the plunger was missing on my choke so i had to use a string to manualy choke the carbs. my mechanic told me the loss of power thing was the stator(400 installed) and the gas coming out of the carb was a hole in the water jacket which eventually led to my bearings goin bad. after you put it in the water drive it for a few minutes the pull each plug one at a time and see if any are wetter than the others. if so then you probably have a hole in the jacket and might want to consider selling the motor before it quits all together.

 

[jimmy120]

Re: HELP.. Mercury 850 (85 HP) Issues

It was not in a fire and I am not sure about it over heating. I was told they can melt if an engine backfires, since I have owned it I have not had it backfire. I don't know if this was preexisting damage or not, because I didn't check out my engine till after 5 runs on the water when I started having issues.

When you say the airbox, are you referring to the metal piece with the 6 holes sticking up?

Clearly your motor need some carb help. Was it in a fire or did it overheat so badly to melt the venturies. The cowl looks to be a 1976/7, but I never saw air boxes like that.

I would take a look at the carbs especially the floats, inlet needles and seats. Also the venturies sit on top of the main fuel nozzle. Make sure they are not clogged by the melted plastic or dirt.

You might post a picture of the carbs w/o the airbox. maybe we can source some venturies for you.

 

[jimmy120]

Re: HELP.. Mercury 850 (85 HP) Issues

I'm working on the same motor right now, those venturies are melted, what you need to confirm is the hole coming up through, it it still ok or melted over, pulling the carbs will tell you. Once you get the carb apart you can shove a nozzle up through the top of the venturies to confirm if the hole is still good(I used the red nozzle from a can of carb cleaner) If I were you I would clear out any melted plastic through the center hole (looking from the front) and call it good. My motor is a 76, look at your starter, it's stamped 76. You need to remove 4 bolts, they hold that air cover on (with the 6 holes) then 2 bolts per carb and the carb will come off, start with the top then remove the bottom, be careful not to break the platic link between the 2 carbs. Inspect the needles in the carb as well as the float, check the pilot jets for crud as well.


Pull the screw out of the fuel pump cover, it's to the left of the switch box. There is a screen underneath as well as an o-ring. Make sure the oring is not compressed and that the screen is clean. Merc dealers sell a rebuild kit that comes with the gaskets and diaphram and check valves for around $25, the diaphram could have hardened from sitting and just needs to be replaced.


These motors take surface gap plugs, I hope that's what you replaced the old ones with.

These motors are renowned for holes in the water jackets, you need to confirm before anything else that it isn't water intrusion into the cylinders, it wouldn't surprise me if that's the issue.

Ok, thanks for the long reply. I will start by removing my carbs and checking them out. I need you to clarify what hole "coming up through" you are talking about. There is a hole in the middle of the melted venturies and a yellow plastic piece in front of the venturies (the jets?).

I have already replaced the fuel pump diaphragm and seals. I completely rebuilt the fuel pumping thinking that was the issue, apparently it was not.

Yes, I replaced them with surface gap plugs.

Do you have a picture of the water jacket? Where is it located on the motor? How do I confirm there is water in the cylinders?

 

[Chris1956]

Re: HELP.. Mercury 850 (85 HP) Issues

The main nozzle is that brass tube that is vertical in the carb throat, and ends at the base of the plastic venturi. Fuel will not flow to the motor at anything above idle if it is not clean and clear. The small brass tube in front of the venturi is some sort of vent for the main jet, I would think.

The airbox is that six-holed thing.

The port side of the motor has the exhaust cover. The cover has a baffle and an inner cover underneath it The baffle and inner cover can rot out, especially in salt water. This causes water intrusion into the cylinders.

Run the motor for a while and them look at the spark plugs. If any look like new, it is very possible water is getting into the cylinder and steam-cleaning the plugs. bad lower crank seals also allow water into the motor, but it only affects the lower 1 or 2 cylinders.

 

[bktheking]

Re: HELP.. Mercury 850 (85 HP) Issues

Chris is spot on.

 

[rinkerdinker1]

Re: HELP.. Mercury 850 (85 HP) Issues

Dude
did you check to ensure your choke is not engaging on the lake bouncing around??? I had a choke solenoid "engaging" when it shouldn't and flopping around with the same exact symptoms only acting up on the lake; the choke lock out feature on my 85hp johsnon solved the issue completly; i had exact same syptoms as you; good luck and let me know!!!
Regards

 

[jimmy120]

Re: HELP.. Mercury 850 (85 HP) Issues

Dude
did you check to ensure your choke is not engaging on the lake bouncing around??? I had a choke solenoid "engaging" when it shouldn't and flopping around with the same exact symptoms only acting up on the lake; the choke lock out feature on my 85hp johsnon solved the issue completly; i had exact same syptoms as you; good luck and let me know!!!
Regards

Your engine was doing the same thing? What did you do to the choke lock out feature that corrected the issue?

I am mildly mechanical, so could you please explain how do I check to see if the choke is engaging or not? The plunger piece that is suppose to go into my choke solenoid fell out a while back, I have the part in my glove box. I am not sure how to get it to stay in the choke solenoid. Could that be the cause?

Thanks for the reply. I hope it is simple.

 

[bktheking]

Re: HELP.. Mercury 850 (85 HP) Issues

Shove it back in, it's magnetic, it should stay in the choke solenoid assembly. The manual choke rod should be enough to hold the choke rod up unless it's bouncing too.

 

[rinkerdinker1]

Re: HELP.. Mercury 850 (85 HP) Issues

I am not educated on Merc's engines OR thier choke mechanism; I am told it's different AND better than Johnson Out boards; it should not matter though as the concept is the same; if your engine is being choked when it should not be i.e. combustion air damper closing; then your engine will behave in this strange manner making you think you have a fuel issue; my mechanic ran my motor for a good long while like I said but the boat was sitting still; when I got on the lake, it was rough out there and the damn choke was "flopping" back and forth to a slightly closed position; hell you could take fishing line and lock that sucker open once she is warmed up and see how your engine behaves on the lake...good luck be safe out there...operation "Dry Water" takes effect this week end I heard

 

[jimmy120]

Re: HELP.. Mercury 850 (85 HP) Issues

I tried shoving it back in, but it does not stay in there. Is the plastic piece that comes off the bottom of the plunger suppose to attach to something? Do you or does anyone have a picture of a choke solenoid and plunger attached to their motor.

 

[bktheking]

Re: HELP.. Mercury 850 (85 HP) Issues

The long plastic rod attached to the enrichener levers on the carbs the there should be a wire going to the manual choke lever if memory serves.

If it's not raining I'll take a pic, it's been hella raining lately.

 

[jimmy120]

Re: HELP.. Mercury 850 (85 HP) Issues

The long plastic rod attached to the enrichener levers on the carbs the there should be a wire going to the manual choke lever if memory serves.

If it's not raining I'll take a pic, it's been hella raining lately.

Thanks. I would appreciate a pic when u get a chance.

 

[bktheking]

Re: HELP.. Mercury 850 (85 HP) Issues

OK I didn't take the pic, I got caught up in repairing mine, I apolgize. Do this on your motor- look at the repair manual for stator testing, there is a high and low side on the stator- blue / blue white is low side (idle), red/red white is the high side. Disconnect the stator from the switchbox and ohm out the stator. I did that last night and discovered the high side was way out, 150K ohms vs the 78K or so ohms it was supposed to be.

 

[jimmy120]

Re: HELP.. Mercury 850 (85 HP) Issues

I replaced the fuel line and primer bulb with a Sea Sense 3/8" line. Took it out today and the problem is still happening. I ordered some used carbs off of ebay, I plan on rebuilding them and installing them.

I opened the motor today (while on the water). I observed the carb spitting fuel while at lower throttle and half throttle, but as soon as you put it to 3/4 or more it would continue spitting fuel at the same pace. However, if I pumped the primer bulb I watched fuel come out of a little hole to the side of the carburetor. I assume that little hole is the high speed jet? If it is the high speed jet, shouldn't it continually spit out fuel while going WOT?

 

[jimmy120]

Re: HELP.. Mercury 850 (85 HP) Issues

OK I didn't take the pic, I got caught up in repairing mine, I apolgize. Do this on your motor- look at the repair manual for stator testing, there is a high and low side on the stator- blue / blue white is low side (idle), red/red white is the high side. Disconnect the stator from the switchbox and ohm out the stator. I did that last night and discovered the high side was way out, 150K ohms vs the 78K or so ohms it was supposed to be.

I have not tested the Stator yet. I am still certain it is a fuel issue, although I could be work. Does the stator control the fuel at all? What is the purpose of the stator?

 

[jimmy120]

Re: HELP.. Mercury 850 (85 HP) Issues

I'm working on the same motor right now, those venturies are melted, what you need to confirm is the hole coming up through, it it still ok or melted over, pulling the carbs will tell you. Once you get the carb apart you can shove a nozzle up through the top of the venturies to confirm if the hole is still good(I used the red nozzle from a can of carb cleaner) If I were you I would clear out any melted plastic through the center hole (looking from the front) and call it good. My motor is a 76, look at your starter, it's stamped 76. You need to remove 4 bolts, they hold that air cover on (with the 6 holes) then 2 bolts per carb and the carb will come off, start with the top then remove the bottom, be careful not to break the platic link between the 2 carbs. Inspect the needles in the carb as well as the float, check the pilot jets for crud as well.


Pull the screw out of the fuel pump cover, it's to the left of the switch box. There is a screen underneath as well as an o-ring. Make sure the oring is not compressed and that the screen is clean. Merc dealers sell a rebuild kit that comes with the gaskets and diaphram and check valves for around $25, the diaphram could have hardened from sitting and just needs to be replaced.


These motors take surface gap plugs, I hope that's what you replaced the old ones with.

These motors are renowned for holes in the water jackets, you need to confirm before anything else that it isn't water intrusion into the cylinders, it wouldn't surprise me if that's the issue.

Fuel is getting through the venturies, I watched it today. I watched the lower carb when hitting it and noticed that it does not spray fuel. This that normal?

 

[bktheking]

Re: HELP.. Mercury 850 (85 HP) Issues

Stator charges the battery and runs power going to the switchbox.

 

[jimmy120]

Re: HELP.. Mercury 850 (85 HP) Issues

Stator charges the battery and runs power going to the switchbox.

Thanks. What issues are you have with your Mercury 850? I really wish I could figure out what is going on with mine. When I am on the water running the motor the highest it will go, it will sometimes sputter like it wants to take off, but doesn't. Where is the high speed jet located? Do think this could possibly be the issue?