9.9 Mercury 4 stroke outboard high altitude jet - www.ifish.net

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Old 06-14-2010, 07:47 PM   #1
sonofacamel
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Default 9.9 Mercury 4 stroke outboard high altitude jet

called a boat shop today that I will not name. Was told that I cannot put a high altitude jet in a newer outboard (2006) due to EPA reasons. Is this correct? If so, how would I get it to run better at high altitude? I had problems just getting the darn thing to start at Diamond Lake weekend before last. But as soon as I get it back to the valley it starts on one pull

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Old 06-15-2010, 04:18 PM   #2
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

This post by PHILP100 may help.
http://www.ifish.net/board/showthread.php?t=306160
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Old 06-18-2010, 11:28 PM   #3
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

it is not a EPA violation to rejet an engine that is running poorly in a high altitude envrionment to correct over rich condition... actually the over rich condition is what the EPA wants you to avoid.. the EPA rule actually states that the manufacturer can only produce XYZ ammoount of emmissions over its entire line. some engines give extra credits, and other models take away... the average is what the EPA looks at... and a poorly tuned engine takes away from a mfg epa rating. they sell and offer high altitude jets, gear sets, and other items to allow the engine to produce the minimum ammount of harmfull emmissions and perform at its designed peak hp range for the model.


in a word you were misinformed...


leaving the stock sea level jetting is actually the "illegal" operation as it negatively effects the emmissions output of the motor... re jetting for the altitude is the proper course of action. just do not forget to put the stock tuning back in for resumed sea level operation.

Last edited by jackr up; 06-18-2010 at 11:31 PM.
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Old 06-20-2010, 12:16 AM   #4
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

What motor (model number)/year is it? While jets definitely affect an engine's ability to run right, when it comes to cold starts you might just need a different approach.
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Old 06-20-2010, 01:43 PM   #5
sonofacamel
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by honker1 View Post
Thanks! I was able to do this today and now have access to the mixture screw. I was told to lean it out at elevation of 5000 feet or over.. I think counterclockwise leans it out but if I am wrong someone PLEASE correct my thinking. I also don't think it would take but an 1/8 of a turn or so.
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Old 06-20-2010, 01:44 PM   #6
sonofacamel
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by MattPark View Post
What motor (model number)/year is it? While jets definitely affect an engine's ability to run right, when it comes to cold starts you might just need a different approach.
I talked to someone at Stevens marine in Tigard last week. They looked it up with my model# and I was told that Mercury does not offer a high altitude jet
for my outboard. Their solution was a 6.5 inch prop (already have one on there) and to lean the mixture out at elevation.
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Old 06-21-2010, 05:29 AM   #7
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by sonofacamel View Post
Thanks! I was able to do this today and now have access to the mixture screw. I was told to lean it out at elevation of 5000 feet or over.. I think counterclockwise leans it out but if I am wrong someone PLEASE correct my thinking. I also don't think it would take by an 1/8 of a turn or so.
COUNTERCLOCKWISE will richen the mix, the screw meters fuel not air...

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Old 06-21-2010, 09:18 AM   #8
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by Smj View Post
COUNTERCLOCKWISE will richen the mix, the screw meters fuel not air...

Smj
Just to clarify the jet chart for altitude starts at 5000' for that motor. Prop change and mixture adjustment are the recommended changes below that
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Old 06-21-2010, 05:38 PM   #9
honker1
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by Smj View Post
COUNTERCLOCKWISE will richen the mix, the screw meters fuel not air...

Smj
When I drilled the plug out, I found that the needle was factory installed all the way in. I always had a problem from day 1 with the slow idle, and hope by turning the needle 1.5 turns counter clockwise that the slow idle will improve, because I wouldn't be able to screw it clockwise.
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Old 06-21-2010, 07:10 PM   #10
sonofacamel
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by Boat Doc' View Post
Just to clarify the jet chart for altitude starts at 5000' for that motor. Prop change and mixture adjustment are the recommended changes below that
I assume when you said "below that" you meant the chart and not elevation.
Otherwise that would be exactly the opposite of what I was told.
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Old 06-21-2010, 07:16 PM   #11
sonofacamel
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by honker1 View Post
When I drilled the plug out, I found that the needle was factory installed all the way in. I always had a problem from day 1 with the slow idle, and hope by turning the needle 1.5 turns counter clockwise that the slow idle will improve, because I wouldn't be able to screw it clockwise.
I hadn't attempted to turn mine since I drilled out the plug yesterday. Went out this evening and was able to turn it both directions.
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Old 06-21-2010, 07:31 PM   #12
sonofacamel
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by MattPark View Post
What motor (model number)/year is it? While jets definitely affect an engine's ability to run right, when it comes to cold starts you might just need a different approach.
sorry for taking so long to reply but I had to get the number off of it.
2006 9.9 (not a bigfoot) Long shaft.

Model # ORO68630
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Old 06-22-2010, 05:34 AM   #13
Smj
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by honker1 View Post
When I drilled the plug out, I found that the needle was factory installed all the way in. I always had a problem from day 1 with the slow idle, and hope by turning the needle 1.5 turns counter clockwise that the slow idle will improve, because I wouldn't be able to screw it clockwise.
When I drilled mine the bit went through the plug and hit the screw juuussst enough to screw it in the turn and a half or so.

I re-adjust the idle mixture each spring to make sure she's good to go on that first springer troll.

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Old 06-22-2010, 12:45 PM   #14
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

[QUOTE=Smj;3172135]When I drilled mine the bit went through the plug and hit the screw juuussst enough to screw it in the turn and a half or so.

I re-adjust the idle mixture each spring to make sure she's good to go on that first springer troll.

Smj[/QUOTE

Thanks for pointing that out to me. It never occured to me that I may have cures the screw to be all the way in, But I bet that is just what happened. With that in mind, I'll work to hit that sweet trolling spot and not screw it all the way in because "THAT THE WAY THE FACTORY HAD IT"
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Old 06-22-2010, 04:03 PM   #15
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Always drill the plug offset a little. If it hits the srew and turns it in it may damage it...by drilling off the center you avoid this...
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Old 06-24-2010, 02:53 PM   #16
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Exclamation Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by smalldog View Post
Always drill the plug offset a little. If it hits the srew and turns it in it may damage it...by drilling off the center you avoid this...
Just to follow up what Smalldog said. Don't damage the screw behind the plug. The screw in my carburetor (I hit it) is still usable, but I thought I would replace it on the next carb rebuilt. I checked with several online Mercury parts websites, and the screw IS NOT available. I guess this would mean a new carburetor. Be careful.
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Old 06-26-2010, 10:03 PM   #17
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

Quote:
Originally Posted by Boat Doc' View Post
Just to clarify the jet chart for altitude starts at 5000' for that motor. Prop change and mixture adjustment are the recommended changes below that
while a printed chart may show this to be true, reality is that if the engine in proper tune shows a rich carb jetting at sealevel the altitude chart will be skewed down in elevation by the number of jet sizes it takes to acquire the proper optimum fuel mix at sea level, so depending on the engine the "5000ft" jet may be actually necessary as low as 2500 ft or lower to properly tune an engine...


if its rich and a smaller jet is available and no ammount of external adjustment will tune out the rich condition it is well worth the time it takes to change it to lean out an over rich condition...

in a word... books dont always reflect reality...

and most of mercury's jets used in their carbs are available in .002 size increments

Last edited by jackr up; 06-26-2010 at 10:06 PM.
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Old 06-28-2010, 07:11 PM   #18
sonofacamel
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Default Re: 9.9 Mercury 4 stroke outboard high altitude jet

seemed to run fine up at East Lake this past weekend.
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