9.9 Evinrude 4 stroke carb modifications for idle

[BAI2]

All,

I have been working on outboards for nearly 30 years. I recently ran into the need to do the carb modification on an early 2000's 4 stroke 9.9.
It worked amazing actually.

My question is why this is needed on a motor that idled down perfectly for more than 15 years, then all of the sudden it needs a hole in the throttle plate to idle it down. I can't wrap my head around this.

Is it due to wear internally? Valves or exhaust?

It feels like we cured a symptom but not the cause.

Thoughts?

 

[cyclops222]

Some problems have more than 1 solution.

 

[jimmbo]

All,

I have been working on outboards for nearly 30 years. I recently ran into the need to do the carb modification on an early 2000's 4 stroke 9.9.
It worked amazing actually.

My question is why this is needed on a motor that idled down perfectly for more than 15 years, then all of the sudden it needs a hole in the throttle plate to idle it down. I can't wrap my head around this.

Is it due to wear internally? Valves or exhaust?

It feels like we cured a symptom but not the cause.

Thoughts?

Where did you come across the Plate needing a Hole?
Perhaps the Engineers decided the Throttle Plate needed to be closed more, in relation to the Idle and Off Idle Ports, and a Hole was needed to restore the Airflow

 

[saltchuckmatt]

If the work around works, why care.......

 

[cyclops222]

When I repaired & improved a machine operation ? I ALWAYS had at least 2 different ways to improve it. I also modified it so I could return to original settings. If my way was not a improvement.

 

[racerone]

I am quite sure there are adjustments to open throttle plate a wee bit.

 

[BAI2]

Apparently I didn’t explain this well enough…. Well maintained motor, very clean and kept used only as a kicker. I worked on it a year ago for a great customer of mine. Thought I had it idling down low enough for him to troll the correct speed for walters. Was better but not slow enough. Adjustments just caused the motor to die. For the previous 15ish years since new, the thing idled down well as it should. We came across the carb mods and as I stated, it worked perfectly. My ultimate question is WHY? What changed with this motor to make this modification needed? Apparently it’s a common issue with this motor as there were instructions on here and Walleye Central. The OCD in me asks the why question.

 

[jimmbo]

Did the Modification and Instructions originally come from OMC/BRP?

 

[saltchuckmatt]

I think you explained it just fine....

Well maintained motor....sure, everyone says that.

Just a kicker.....yeah, kickers don't work hard.

Worked on it a year ago.....that's quite a while. Do you know how fast gas turns to varnish?

What changed this motor.....it's older, it's used and it might have old gas, stuff in carb.....none of this surprises me.

I'll check my crystal ball and see what it says.....!

 

[matt167]

Considering it’s actually a Suzuki, I think it’s known the carbed models were a little finicky. Great motors though.

3 things happen to make a carbed engine run. Fuel, air and spark. My guess is the carb runs a little leaner now, causing it to run faster.. the good thing is, as long as you find a good dealer, the parts on the Suzuki side should be available

 

[racerone]

Sure it is a Suzuki ?----Have not seen a model # on this one.-----Not sure if EVINRUDE marketed the rebranded Suzuki 9.9 models.----Johnson did for a few years.

 

[matt167]

Sure it is a Suzuki ?----Have not seen a model # on this one.-----Not sure if EVINRUDE marketed the rebranded Suzuki 9.9 models.----Johnson did for a few years.

Well you’re right. It could be a Tohatsu mfg. BRP years would have been Tohatsu. But I think there was a transition period where BRP was building and servicing the old OMC stuff before the Etec released

 

[racerone]

The early JOHNSON / EVINRUDE 4 strokes were their own design I believe.-----After all they used the ( modified ) 2 stroke carburetors and familiar lower units.----Ignition components were also similar to 2 strokes.

 

[BAI2]

Did the Modification and Instructions originally come from OMC/BRP?

No they did not. At least not that I am aware of.

 

[racerone]

These motors may have had a history of rocker arm wear.-----Checked valve clearance on it or just drilled the hole ?

 

[BAI2]

These motors may have had a history of rocker arm wear.-----Checked valve clearance on it or just drilled the hole ?

Just drilled the hole. If the modifications wouldn’t have worked I would have dug deeper.

 

[cyclops222]

So how much should a good running 2 stroke idle mixture screw be between slight LEAN miss and too RICH blubber starting ? How far out from Idle needle fully closed. While idling in gear in open water.

 

[saltchuckmatt]

It's mostly done by look, listen and feel.

For those loosing or that never had that 6th sense, on 2 strokes, clockwise until the lean sneeze than 1/4 turn counter clock......and wait 30 seconds. Than micro turning until you get lucky.

It takes time to find the "sweet spot" brings a smile to anyone's face

 

[racerone]

We are talking 4 stroke on this thread.----The book shows an idle mixture screw.----The book shows an idle speed screw.--------Books says 4/5 turns out on the idle mixture screw.----Idle speed screw limits closing of throttle plate I believe.

 

[BAI2]

These motors may have had a history of rocker arm wear.-----Checked valve clearance on it or just drilled the hole ?

And thank you for the most helpful reply. Even though I have been in this business for many years I still do not know everything about all of them. I have a very blessed reputation locally that I have earned to the point sadly I turn people away as I just can’t do it all. This one motor had my head spun out a bit. Thinking through your response it adds up. Internal wear on the valve train. Thank you.