78 johnson 85hp stalls out at random

[Clemak]

Hey everyone. I just bought a used boat having an issue with stalls and ending up with a dead battery. First time on the water it ran like a bat outta hell for the first 15 min then wouldnt go past 1/4 throttle without stalling for 20 min then wouldnt stay running at all. Killed the battery starting it up so many times. Ran it in the driveway with the hose and it was fine for about 7 min and i shut it off as to not **** the neighbors off. 2nd time out after sitting a week and i charged the battery back up it wouldnt stay started at all. Im inexperienced with outboards but am mechanically inclined. Can anyone help as to where i should start?

 

[racerone]

Mixing the gas / oil at 50:1 ?----Water pump impeller replaced ?-----Start the trouble shooting with a compression test.----Post your numbers.----Careful with all the cranking as these starters are easy to burn up !!

 

[F_R]

So now it won't run at all? Good. That makes it easy to troubleshoot. Compression first, just because that's good practice. And while you are doing that, check for a 7/16" spark on all cylinders. I'm betting it flunks the spark test. Or you have a fuel tank full of water. Well maybe not "full", but a gallon or so.

 

[Clemak]

It will run for a minute or so but i have to baby it with the electric choke. Then it stalls. And i have to keep doing it and it will kill my battery. From my general knowledge on motors it acts like fuel starvation. How hard is it to clean the carburetor?

 

[Clemak]

I did buy new plugs to put in and a new rectifier because i found a great deal on one. Water impeller im assuming is good because i have steady stream of water spitting back out

 

[Bosunsmate]

It will run for a minute or so but i have to baby it with the electric choke. Then it stalls. And i have to keep doing it and it will kill my battery. From my general knowledge on motors it acts like fuel starvation. How hard is it to clean the carburetor?

Not so hard, just involves undoing a few bolts to get it off and making sure you note where everything goes. You should spray carb cleaner or like wd40 down every jet to make sure it blows clean out another exit hole somewhere. People often just soak them but you really need to do that. Id also check your fuel tank for debris and the fuel bowl in the carbs too often provide a easy give away as to what could cause a blockage

 

[F_R]

Go ahead and do what you are determined to do. Then if you find no problem with the carburetors, maybe you will back up and make the simple checks previously mentioned.

There are two carburetors on that engine. Each one is essentially two carburetors sharing a common float bowl. So you figure all four are plugged up?

At least remove the hex drain plugs at the bottom of each carb and see what runs out. Hopefully it isn't water. While you have the drain plugs out, take a look at the end of them. They should be shiny new looking. If they are coated with a varnish-like substance from old rotten gas, then I concur---the carbs do need cleaning.

 

[Clemak]

If compression was bad it wouldnt run at all correct? It will run on its own for about 10 to 15 seconds before stalling. Maybe longer if i keep pressing the electric choke on and off. Once i stop cause it sounds like its running good it bogs back down and stalls. And where can i find manufacture specs for the correct gap for the new plugs?

 

[F_R]

A compression check is just one of common sense preliminary checks. Other things can reveal themselves during the process. Faulty spark that I suggested for one. Water getting into the cylinders for another.

 

[racerone]

Trouble shooting needs to be done.----These motors will actually run on 2 of 4 cylinders !

 

[Clemak]

I will look into all of that when i get some time. My daughters have ke running all over hell the next 5 days or so. I wont get a full dedicated day for it all untill next weekend.

 

[Clemak]

1978 Johnson 85hp

So I bought a boat with a 78 Johnson 85hp outboard. Model 85ml78c. Initial run was fine for about 20 min until I turned around to head back to the dock and it cut out and wouldn't go past about 1/4 throttle after that without stalling. I ended up killing the battery cause I had to start it back up to many times. I used my trolling motor to get back to the launch. Charged my battery and hooked up the hose a few days later and it ran like a bat out of hell. A week later I took it to the launch and it wouldn't stay running longer than 10 seconds...even with tapping the electric choke. Which I had to push the choke to keep it from stalling for that short period of time. Is this a bad fuel oil mixture issue? Carb issue? Plugs? My compression tests at 90 in 3 cylinders and 87 in the other. Plugs looked like a normal plug would. Carbon and a little oil residue on it. I bought plugs but need to find spec on gap before I install them. Bought a rectifier cause I stumbled upon a new one on sale while i was shopping.

Any recommendations or ideas on where to start would be appreciated.

I plan to rebuild the carbs next week when I get my rebuild kits in.

 

[jbcurt00]

Merged dup topics and corrected the title to be a 1978 Johnson

 

[Clemak]

I'm having trouble finding my own post. That's why I reposted again. Sorry. I'm learning how to use this platform. I just wanna ask people for advice

 

[thatone123]

I'm having similar problems with a 75 hp 1982 model. Runs good at medium/high RPM but will not keep running. Waiting for carb kits,