How to tell if it's too rich or lean

[Holy Mackinaw]

I've got a '68 seahorse 9.5hp, how can I tell where to set the slow speed mixture dial? also can I use XD-50 or even XD-100 oil in the gas? I personally prefer not to smell a lot of burning oil, and this engine has a good amount of carbon build up that i'm going to sea foam it in a week or two.
Merry Christmas to all.

 

[F_R]

Re: How to tell if it's too rich or lean

The knob only affects the slow idle mixture. If it's too lean it will cough and probably stall. With the motor on a boat in the lake, and warmed up, slow it down to idle and turn the knob to the right (lean) till it coughs or sneezes, then turn back to the left till it runs smooth. Then forget it unless something major changes like temperature or altitude.

 

[Texasmark]

Re: How to tell if it's too rich or lean

I use syn or syn blend oil as I have found it to foul less and produce less smoke that you refer to. So much so that I can be idling for a bit and hammer down on the throttle, look back and not see any smoke cloud like I used to. The Sea Foam definitely helps too as I keep it in the gas.

On 50:1 or 100:1 you have to look at the oil and the engine for compatibility. Surely the less oil you burn, the cleaner everything is.

Mark

 

[ezeke]

Re: How to tell if it's too rich or lean

In addition to using synthetic oil, having a good working thermostat will cut down on the smoke and carbon on the 9.5.

Be sure that the thermostat is 143?. The Mercury Marine part # 75692 works really well for half the price.

 

[Holy Mackinaw]

Re: How to tell if it's too rich or lean

Where is the thermostat on this motor, I have the service manual but do not recall seeing it in there.

 

[steelespike]

Re: How to tell if it's too rich or lean

Where is the thermostat on this motor, I have the service manual but do not recall seeing it in there.

Thermostat is located near the top of the cylinder head it appears to have a somewhat triangular shaped cover.
Initial setting of idle mixture scrtew is 3/4 open from gently bottomed.
Then in gear warm at idle adj. to the best operation.too lean it will be rough
may sneeze and stumble on acceleration or stall,too rich it will be smokey,may lope or shake and will tend to shudder or(4 stroke) on acceleration.You may have to remove the knob until you get the final setting then replace in the middle position.
Synthetic oil burns cleaner and is said to be biodegradeable.