# Trouble starting 4stroke high elevations



## aeviaanah (Jul 31, 2013)

Going camping this weekend and I had trouble starting my outboard at this elevation. Motor is 2012 Mercury 15hp 4 stroke. Starts fine at 100ft elevation but takes tons of electric start/pull start to get goin at 5700ft. After I get it goin it seems to run fine. Any suggestions to getting it started easier? Any suggestions would be greatly appreciated.


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## nomowork (Jul 31, 2013)

Choke?

I have a three year old Honda four stroke 15hp that always had trouble starting in Mammoth at about 7000-9000 feet elevations. Mine is a pull start and my arm always had a good work out.

Funny thing is that we just came back from Mammoth last week and it started on the first pull every time until the second day when it wouldn't start at all. I have a thread going under motors. I still haven't been able to get it started but am slowly isolating the issue.

At least you have an electric start!


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## aeviaanah (Jul 31, 2013)

It has a choke and I Try to start it in different positions. I haven't been able to figure out which position is best. Is this a flaw or a normal problem with these motors?


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## nomowork (Aug 1, 2013)

Carbed motors are very touchy animals in cold and high altitude situations. I usually just pull the choke all the way out to get it running initially. 

My other boat has a two stroke direct injected motor and fires up easily (electric start). 

My carbed motor will be the last of it's kind for me.


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## San Dimas (Aug 1, 2013)

My 2013 9.8hp Tohatsu starts fine at Mammoth. I pull the choke all the way out and as soon as it starts push it all the way in so it won't flood. Don't use the choke the rest of the day.


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## lovedr79 (Aug 1, 2013)

sounds like mine used to. i have the not so electric choke. come to find out basspro rigged it with the wrong power cable. i made a manual choke out of a piece of stainless rod. starts great now that i know that the choke is working. i hadnt given it much thought until i had the cover off, choke "on" and the choke didnt move, then it dawned on me. i checked and sure enough they used a 8 or a 9 pin cable and it should be a 10 or something like that.


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## bcbouy (Aug 1, 2013)

you need to re jet the carb for high elevation.i have the same problem with my generator and outboard when i'm high elevation camping/fishing. it runs really rough and not very fuel efficient.


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## lovedr79 (Aug 1, 2013)

you may also have to re-jet the carb. we used to have to re-jet our dirtbikes when we would go from sea level to riding in the mtns. of Colorado.


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## turbotodd (Aug 1, 2013)

Rejet may be required for elevation-contact a dealer for more info about this. Usually a higher altitude dealer will know more than one on the coast. Also-if these have a compression release (automatic, or ACR), it may affect how it starts at elevation. Used to some bikes had an ACR that was slightly different for higher altitude operation. They may generate 90 psi compression at sea level, but at altitude might only make 75-which can lead to harder starting when combined with improper jetting. I've done a few Kawasaki's like that. Not outboards obviously, however similar principle.


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## aeviaanah (Aug 1, 2013)

Thanks everyone. Ill look into rejetting, ill just run it as is this weekend. It seems to run great once I get it started. Wont hurt the motor any will it?


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## Andrew04 (Aug 2, 2013)

the friction of the air molecules rushing through the venturi and over the jet actually "grabs" fuel molecules and sucks them into the cylinders. At higher elevations, there are less air molecules flowing through, but the jet is still allowing the same amount of fuel to enter, thus leading to a rich condition. Not dangerous, but inefficent, and unreliable. If you do correct with a smaller jet for higher elevation, do not use it at sea level as you will be way lean.


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## Country Dave (Aug 2, 2013)

_Well I’m not an outboard expert but when you’re at altitude the air is thinner/less dense,

So to get a good air fuel mixture you need the fuel mixture to be leaner not fatter/rich. Choking a motor makes the fuel mixture richer because that’s what a cold motor needs, a little bit richer fuel mixture until it warms up. 

If you choke a motor at altitude you’re making an already rich fuel mixture even richer. 
Try open up the throttle plate a little when cranking and that will let more air into the motor. Don’t choke it. Check with the manufacture and see what there recommendations are. _


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## PATRIOT (Aug 2, 2013)

This is the main reason my next new motor will have direct fuel injection and a MAP sensor.


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## Country Dave (Aug 2, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=324583#p324583 said:


> PATRIOT » Today, 14:15[/url]"]This is the main reason my next new motor will have direct fuel injection and a MAP sensor.



_Yep a MAP sensor, a BARO sensor a water temp and or cylinder head temp sensors, throttle position sensor and exhaust oxygen sensor. That's the only way the Engine Control Module/ECM can know how long to pulse the fuel injectors on for. Now I know someone is going to say this ( Just more stuff to go wrong) 

Not so much, Yamaha and Mercury have a great track record for reliability and very low failure rate on sensors and control modules. _


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## turbotodd (Aug 5, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=324591#p324591 said:


> Country Dave » 02 Aug 2013, 12:34[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=324583#p324583 said:
> ...



Fuel pumps and injectors are a different story, however not the fault of the manufacturer. More a fuel quality problem than anything. Old stale fuel WILL plug a pump screen and injectors in no time flat. Difference between carb'd motor and EFI motor (in this example) is cost. Clean a carb for under $100. EFI parts replacement $250-$1200. One more reason to stay on top of your fuel quality!

That said, I'd have an EFI motor any day over a carbureted motor!!!


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## Country Dave (Aug 6, 2013)

Fuel pumps and injectors are a different story, however not the fault of the manufacturer. More a fuel quality problem than anything. Old stale fuel WILL plug a pump screen and injectors in no time flat. Difference between carb'd motor and EFI motor (in this example) is cost. Clean a carb for under $100. EFI parts replacement $250-$1200. One more reason to stay on top of your fuel quality!




That said, I'd have an EFI motor any day over a carbureted motor!!![/quote]

_A couple thoughts,

Most of the engine related issues that the marine industry is seeing right now is a direct result of the ethanol that’s now in our fuels. We can rightly translate ethanol into alcohol, and alcohol absorbs moisture and therein lays the problem. Yes “old stale fuel” will gum up a carb, and it can clog up filters and screens. Whether it’s a fuel injected motor or a carbureted motor we have to be mindful of all of the fuel related issues. 

However when you factor in all of the variables, fuel injected motors are far more cost effective to own and maintain than there carbureted counter parts. That’s true even if you considered nothing other than fuel economy. But the truth is there are many other things to consider than that. It’s all relative to ones individual ability to maintain and repair his or her motor. 

Yeh you can by a can of gumout, spray your carb and maybe get enough of the chit out of it to make it idle without staling but the reality is, it moist likely needs to be overhauled. That’s not a big deal if you have the skill set, the carb kit is probably under a $100 but if you have your local marina do it you looking at more like $250 
A fuel injector on the other hand can be professional cleaned and flow tested for about $10 a piece. 

Again it’s all relative; you still have to be able to diagnosis the issue, remove and reinstall the injectors. So what’s the Synopsis, ”An ounce of prevention is worth a pound of cure” in other words, carbureted or fuel injected marine application motors need to be maintain in a way as to prevent fuel related issues. Firstly we do this by getting our heads out of our Azz’s and be mindful that it’s a real problem. 
\
Good fuel additives like marine STA-BIL and Star Tron are a must, even if you don’t winterize or leave your boat idle for long periods of time in between use. Another prevention method is to keep your fuel tank full. When the tank is full of fuel there isn’t any room for air so the ethanol can’t absorb what’s not there. Fuel injected motors are the future, and just like anything else they need to be well maintain for longevity and performance. Just my 2 cents……………………………………… :mrgreen: _


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