I know this isn't the mechanics page, but....

[mrwillis]

I NEED A QUICK ANSWER! I know that I have a little problem, and I don't think it is a large one. It started happening after I bought a batch of bad gas, and I don't understand it. I have a 20hp 87 Johnson, and at low idle (like in a no wake zone), it will "cough"...almost cutting out. But, then, as I give it a little more idle and get up to speed it runs perfectly fine.
This motor runs GREAT! However, after this bad batch of gas, it ran rough...

So, I am sure it is in the carb, and something not too major. But, i was reading about cleaning out a carb with seafoam...FOR EXAMPLE, something about running an extremely rich amount for a couple minutes with your gas, then shutting it off, and then blowing the "black" out? I don't remember what exactly i read, so that is what I ask.

What are the keys to this? I have a guy willing to rebuild my carb, but I don't have that money, and would hate to have to do that if it isn't necessary. Any thoughts would be great. I need to do something tomorrow, as the guy said he could get to my boat by Wednesday. Also, if I do this, do i run my regular oil/gas mixture, then add the seafoam to it?

I run stabil and seafoam (the recommended amount) in every tank and will continue to do so. I've done this for 10+ years, and the two motors I've had run perfectly, until I got some bad gas.

So, any helop would be GREATLY appreciated. I have some youth group kids that want to go fishing Saturday!

Mrwillis

[FourRods]

I am no expert but I do have a few questions. How long ago did you get the bad gas? Did you get it all out of the lines? Have you checked the spark plugs since this started? It doesn't take much to foul a plug and once it is fouled, it usually needs cleaned with a wire brush to get all the junk off of it. I would make sure all the bad gas is gone from the lines and then check and clean the plugs. It would be cheaper than getting the carb redone.

FourRods

[huntinslabs]

Run seafoam at double dose or stronger for a while and then let sit overnight, then run it like ya stole it for a bit and hopefully that clears it. If not ya might have to clean the carbs. Them little jets clog pretty easy. And yes also use your normal oil ratio. Hope this works for ya.

[sparkie51]

Did you check the filter in the fuel pump? Little screen gets clogged sometimes and will present problems that mirror bad carbs. Could be a small flake of hose or debris is blocking filter and when you give it the throttle enough gas is allowed to run the motor at a higher speed.

Get a gas can and put 1 gallon of gas and seafoam in it and run it. Will clean jets. Go heavy on the seafoam.

[Powertroll]

How to decarb an engine/ Dunk's method - The Hull Truth - Boating and Fishing Forum

X2 on the plugs and filter. I use the Seafoam trick mid season because I troll ALOT and it does a great job. evrything you need to know is laid out step by step for ya.

[Fishingmmaddog]

The cough is low speed adjusted to lean,richen up your idle mixture

[jpdawg]

What Fishingmmaddog said.

[anvil]

I NEED A QUICK ANSWER! I know that I have a little problem, and I don't think it is a large one. It started happening after I bought a batch of bad gas, and I don't understand it. I have a 20hp 87 Johnson, and at low idle (like in a no wake zone), it will "cough"...almost cutting out. But, then, as I give it a little more idle and get up to speed it runs perfectly fine.
This motor runs GREAT! However, after this bad batch of gas, it ran rough...

So, I am sure it is in the carb, and something not too major. But, i was reading about cleaning out a carb with seafoam...FOR EXAMPLE, something about running an extremely rich amount for a couple minutes with your gas, then shutting it off, and then blowing the "black" out? I don't remember what exactly i read, so that is what I ask.

What are the keys to this? I have a guy willing to rebuild my carb, but I don't have that money, and would hate to have to do that if it isn't necessary. Any thoughts would be great. I need to do something tomorrow, as the guy said he could get to my boat by Wednesday. Also, if I do this, do i run my regular oil/gas mixture, then add the seafoam to it?

I run stabil and seafoam (the recommended amount) in every tank and will continue to do so. I've done this for 10+ years, and the two motors I've had run perfectly, until I got some bad gas.

So, any helop would be GREATLY appreciated. I have some youth group kids that want to go fishing Saturday!

Mrwillis

Did this gas have water in it dirt or smell bad? If not then it was not the gas. The first thing to try and do is adjust the low idle speed screw it is right there in the front, Screw it in easy until it stops and back it out 2 1/2 turns and try your motor. 2 to 21/2 turns usually the sweet spot for these engines.You can use this for parts lookup and see how things are made you will have to match you I D tag to the numbers listed for the right motor. Johnson Outboard Parts 1987 It is cheaper to order parts then it is to go to the local boat shop and buy them..

I didn't read all the responses but I have the same motor does the same thing and I change out the plugs from champion to NGK it runs 10 times better oh set the gap @ .030 30 thousands. I have rebuilt my carb , LOL it is a crime what they charge people to rebuild a carb on these little motors and there is nothing to them. Mine still has that little cough and I was told there is nothing I can do for it because the old motor is old. The fuel pump works off of case pressure or should I say back pressure and when the rings get wore down it loses some of this pressure and does not feed enough fuel to the carb it runs lean and coughs on way you can check this is when it does it is your pump ball tight or can you pump up the carb..
I hope this helps.

[scottcrappiegirl]

sea foam works wonders..same oil to gas mix

[slickwater1]

lean cough. richen up.