140HP Johnson smoking at low/idle speeds

[marclee]

Good day all<br />I have a 140 Hp 1987 Johnson motor that has started to smoke a fair bit at low/idle speeds. It has only started recently as last season it was fine. I have checked the compression ratios and all cylinders are within 10psi of each other. The readings were 130,130,130,135 Psi. The motor starts fine with no problems it will run fine all day but is always smokey at low/idle speeds. Carbs were redone in October last year. It has not had a service for 1 year. Water pump is still pumping a good volume of water. The smokey situation starts when it is cold or hot. Could some one possibly shead some light on this for me.

 

[MCM]

Re: 140HP Johnson smoking at low/idle speeds

Hi budda, when were the plugs changed last? what condition are they in? what plugs are they? have you had it decarbed recently? are you pre-mixing or using the VRO?

 

[marclee]

Re: 140HP Johnson smoking at low/idle speeds

Hi Mike, The plugs are about 1 year old and they still look to be in good condition. No fouling visible and no oil build up apparent.The decarb was done about 7 months ago. I Pre mix my fuel due to past problems with VRO it was removed. I am mixing at 25:1. All fuel lines were replaced 6 months ago due to them starting to break down and rubber ending up blocking fuel system. I had the boat out yesterday and it is now running ruffer at idle but as soon as I accelerate it runs fine.<br />Thanks Budda.

 

[Dhadley]

Re: 140HP Johnson smoking at low/idle speeds

Its supposed to act that way at 25:1. Very normal. <br /><br />What plugs are you using? What oil? Why not 50:1?

 

[marclee]

Re: 140HP Johnson smoking at low/idle speeds

Hi Dhadley, Sorry I made an error I am running at 50:1. The oil is castrol outboard 2 stroke oil at the moment but in the past seasons I have used shell nautalis. I have used castrol for this season and up till now has not been a problem.

 

[CORE]

Re: 140HP Johnson smoking at low/idle speeds

Marclee, I have the exact motor and year & have the exact same issues. I am curious to see what replies you get for a solution. If you find a cure for the problem off this forum please let me know and i will do the same.

Thanks,

 

[tx1961whaler]

Re: 140HP Johnson smoking at low/idle speeds

4 year old post......

 

[ezeke]

Re: 140HP Johnson smoking at low/idle speeds

To CORE:

I have the 1988 big bore version of the same motor and I troll a lot. Here's what I found.

I got the least smoke, carbon build-up, fouled spark plugs and fouled recirculation check valves with the following:

Synthetic or Synthetic Blend TC-W3 oil;

Switched to 0434137 (black) thermostat assembly;

Run Carbon Guard or Ring Free constantly;

Champion QL77JC4 plugs.

If you use BRP XD-50 oil it has the carbon treatment built-in and is a synthetic blend. My results were just as good, maybe better, running Pennzoil Synthetic Blend (owned by Shell, who also make Nautilus)

I find that I have to service the recirculation check valves after a shock de-carbon treatment; some are always clogged up which causes more smoking, especially at startup.

My motor hates running cold, so I am very careful to monitor the temperature.

More often than not, rough idle is caused by the throttle plates not being synchronized.

 

[CORE]

Re: 140HP Johnson smoking at low/idle speeds

Ezeke:

wow, thanks for the info.
the boat is a lund tyee 18. traded a gun for it ($800) and have been running it several years now with out any break down cost. Just need to take your suggestion and hopefully helps with the smoke.