73 Evinrude 115 - Running good but there is always a gas / oil slick and plugs soaked

[BOAH]

I have a 73 Evinrude 115 and I've noticed that when I'm sitting still idling and also after I shut the motor off, there is gas and or oil in the water around the motor. I can't see anything obvious that is leaking and actually the motor seems to be running really well. It can take a little longer to get it started when it's cold but I've found that if I pull the plugs and clean them, it starts quicker. And when I pull the plugs, they're always wet. I rebuilt the carbs about a year ago and set the floats to parallel with the bodies. Cleaned everything to the best of my ability.

Again, I hate to mess with it too much since it's running so well but it appears I need to. Any suggestions?

As always, thanks for your help!

 

[fireman57]

Re: 73 Evinrude 115 - Running good but there is always a gas / oil slick and plugs so

the older outboards always had an oil slick behind them. If things are fine leave them alone. It is just unburnt fuel.

 

[emdsapmgr]

Re: 73 Evinrude 115 - Running good but there is always a gas / oil slick and plugs so

Those engines run rich at idle. Not unusual for the plugs to look wet if you pull them at idle. That's normal. It's another story if you do a high rpm throttle chop and then check the plugs-they should be dry and a light tan. Check your airbox drain hose to make sure it is intact and connected. It is supposed to run from the bottom of the airbox to a hose barb at the bottom of the block. It recirculates any excess fuel from the carbs back into the combustion of the lowest cylinder. If the hose is missing or leaking, fuel can leak down the midsection into the water. In the later years OMC put an airbox gasket between the airbox halves. This further prevented any fuel/oil mix from dripping down onto the lower cowling. Your model does not have one.

 

[Haffiman]

Re: 73 Evinrude 115 - Running good but there is always a gas / oil slick and plugs so

Which plugs are you using?
The original set up recommendation is UL77V.
The work reasonable well as long as engine has the correct temp and the original compression.
The next alternative which runs slightly 'hotter' and may improve the idling characteristics is is QL 16V. Even this a surface gap plug.
As an 'emergency', mainly intended for those with extended idling like trolling etc, even (Q)L77JC4 may be used. That plug may however have a rather short life time if running full power.
Is your thermostat system in good condition?
Test engine temp particularly at idle and be sure the cylinder head temp gets UP to correct working temp.

 

[F_R]

Re: 73 Evinrude 115 - Running good but there is always a gas / oil slick and plugs so

If it is running well and no external fuel leaks, get used to it. It is a two-stroke, and that's what they do. That oil that you put in the gas does not ALL burn. The rest goes out the exhaust and just a drop of oil will make a big oil sheen on the water. BTW, if ALL the oil did burn, it probably would sieze, or at least wear excessivly, from lack of piston lubrication.

Surface gap plugs do not get hot and burn the oil off, so they will be wet. Gap-type plugs don't get hot enough at idle to burn it all off either. If they did, they would be too hot at high speed and cause pre-ignition, probably destroying the engine. Both types depend on the high voltage, fast rise time of CD ignition to fire in spite of the crud.

 

[BOAH]

Re: 73 Evinrude 115 - Running good but there is always a gas / oil slick and plugs so

That's fine with me and in fact, I'm more than OK with it. I appreciate the feedback. And I will check the airbox drain hose just in case. Thanks again!