1975 Evinrude 9.9 no start

[flyingscott]

Lean Fuel Mixture


A common cause of overheated pistons relates to insufficient fuel delivery to the cylinder to keep the temperature down. Idle mixture screws that have settings which are too lean will cause a lean air/fuel mixture, and too much air in the combustion chamber causes the temperature to rise. Kinked fuel lines and clogged fuel filters will also starve the cylinders. A rich, or wetter mixture counteracts the condition.
https://itstillruns.com/causes-up-pi...r-8669199.html

This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information

Truth is you dont know your a** from a hole in the ground bud

How.does the.low speed adjustment cause a lean condition that will damage the motor? The.low speed adjustment has absolutely no effect on high speed operation. The only thing that can cause a lean condition at high speed a plugged main jet. You cannot run a.outboard lean at an idle to cause damage. There is just not enough heat created to at around idle.speeds. You may want to look at how your carb actually works.

 

[Newyota]

Also if the entire engine is verifiably the same part by part with the only difference being the model plate and the carb you do the math. That model plate doesn't make the carb incompatable

If I missed it in all the banter here sorry, but are you running this in a tank or muffs?

 

[kalebg]

Newyota Im actually just using the muffs.

 

[flyingscott]

Newyota Im actually just using the muffs.

That will run it lean enough to ruin it. Should google back pressure for the internal combustion engine.

 

[kalebg]

Literally everyone: You cannot damage an outboard by running lean, run it more lean. New guy comes in asking a super basic setup question Flyingscott: "That will run it lean enough to ruin it"

 

[kalebg]

Also the high speed jet handles 30+% throttle. Given the max HP at 5500-6500RPM id be trolling just below that high speed jet threshold running lean for hours on end and could have eventual heat soak in the pistons. Remind me again how hard it to to read plugs and set correct burn or worst case ignoring that and just cleaning plugs once in a while vs the cost of possibly rebuilding a motor

 

[flyingscott]

Get a.mechanic because.you have no idea what the hell you are talking about!!! Good luck with your motor.you will need it. There is.a.reason it does not run right and it.is.all you.

 

[kalebg]

*looks at posted links from literal mechanics*

 

[kalebg]

*looks at the running motor assembled single piece by single piece* *looks at hands holding no manual* yeah looks like i did good. Especially considering the not perfect idle is most likely due to being run on muffs as Newyota jumped in and asked about. Whats a mechanic going to say lol, hey i pulled your plugs looks like your running a smidge rich. Not that itll hurt the motor, you just have to clean them marginally more often so i turned it 1/8 turn

 

[kalebg]

Take whats left of your pride Mr: "But its not OEM" Your ignorance betrays you with your dependance of MFG knows best instead of knowledge you can call your own. Cant expect you to actually know anyhting besides just repeating what ever backwoods shade tree knowledge you might have

 

[oldboat1]

My early to mid-1980 9.9 Yachtwins use the 15 hp carb body with it’s larger throat, and a larger jet. The idle is very low and smooth — have a regular ’91 9.9, and the idle is the same as far as I can tell. I’ve guessed that the extra long Yachtwin shaft full of water provides added back pressure, calling for a larger carb and jet to match performance of a regular 9.9.

My side-by-side idle comparison was in a barrel, not on a boat. (Happens I was working on both of them last year just for prepping.) It’s debatable whether the 25” Yachtwin shaft required the larger carb to compensate for added back pressure . But in fact that’s the way the Yachtwins left the factory.

You cannot properly tune an outboard on muffs, though, because muffs do not provide sufficient back pressure — better in a barrel, best on a boat in the lake.

So this entire thread finally points to the issue of back pressure — tuning problems, carb selection. It’s all come together nicely, IMO….

 

[tomhath]

Take whats left of your pride Mr: "But its not OEM" Your ignorance betrays you...

This guy is obviously a troll. No more replies from anyone please.

 

[oldboat1]

Nah. Let it go, Tom (or not). Leave it to the mods. -- flag posts if you want some kind of action. JMO.

 

[flyingscott]

It.always amazes me when posters insult the contributors when they get the answer they don't want. But what is shi##y is when regular contributors defend these A-holes. I dont know if it is because they are lonely or need ahug. But how about you knock.it off.

 

[oldboat1]

No hugs these days. Not even a handshake.

 

[Tim Frank]

Lean Fuel Mixture
A common cause of overheated pistons .....blah....blah....A rich, or wetter mixture counteracts the condition.
https://itstillruns.com/causes-up-pi...r-8669199.html

This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information

Truth is you dont know your a** from a hole in the ground bud

From their website..... " It Still Runs is the go-to destination for all things cars."

I guess the obvious question is ... when you have the authoritative source for "all thing cars" at your disposal, why would you need to come to a boating forum to get answers about an outboard problem ?

 

[oldboat1]

All those running 50 and 60 yr. old 2-stroke kickers that keep showing up say something about the longevity of those little buggers. Some reasonable care and they go on for another decade.