1984 yammy 115 rough idle

[lingcod]

have had both upper and lower carbs rebuilt.manual says idle speed is 700 rpm. if I try to go that low it just shudders, sneezes and dies. lowest I can get is 1050rpm. will the carb adjusment screws help? if so how many turns out on each. the book says 1 5/8 turns out but this doesnt seem to help any. Im fairly new to outboard repair but very adept at auto repair just not too familiar with what does what on an outboard.

 

[Ray Neudecker]

Re: 1984 yammy 115 rough idle

The out of gear idle should be at or slightly below 1000 rpms. 1 1/4 to 1 1/2 from a soft stop for the idle air adjustment. Need to check the timing adjustment for idle also.That has a tendency to vibrate out of adjustment over time. You also need to check the fuel pumps.

 

[rodbolt]

Re: 1984 yammy 115 rough idle

same thing<br /> suck,squeeze bang and blow.<br /> no different than the basic operation of a car. you need to study on the differences on the priciples of operation of the various designs.<br /> that cough your hearing would be flame out the carb on a 4 stroke. its caused by a lean mix in the crankcase. I would imagine your idle jets are still clogged. they are tiny.<br /> the "mixture screws" on that carb dont control the air to fuel ratio only how much is passing the needle. you may have to increase your idle jet sizes a small amount if the piston skirts or cranks seals are worn. but as far as working all internal combustion engines have the same set or principles.

 

[lingcod]

Re: 1984 yammy 115 rough idle

this motor has never idled right. I have owned it for 4 years. 2 complete carb rebuilds both times occumpanied by full tune-up and motor check. good compression all cyl. motor runs like a champ above idle. best running 2 stroke i've ever owned except for idle. awfully tough to park in the marina when it keeps cutting out on me.I guess I'll have to take it back to the shop.

 

[douglloyd]

Re: 1984 yammy 115 rough idle

I've got the same motor same problem. What was the final solution on yours? Thanks.

 

[lingcod]

Re: 1984 yammy 115 rough idle

never have fixed it completely. did the seafoam trick, that helped a little. just left the idle speed up around 1000rpm. learned to live with it. now ive got other issues with it such as starving for fuel at WOT. still tracing that one out.<br /><br />lingcod

 

[fishon71]

Re: 1984 yammy 115 rough idle

"now ive got other issues with it such as starving for fuel at WOT"<br /><br />I just went thru this with my 1988/130 HP Yamaha, it was a clogged needle seat on one carb, the water test, hooking carb to garden hose found the problem, a great test if your gonna pull the carbs all appart again. I soaked (Napa carb Cleaner) them, probed, blew & blew, got em clean, runs great now!

 

[lingcod]

Re: 1984 yammy 115 rough idle

whats this water test? I'm gonna pull the carbs in a couple of weeks and would like to do all possible fixes before summer salmon season<br /><br />lingcod

 

[douglloyd]

Re: 1984 yammy 115 rough idle

If you have Fresh fuel/oil, Water seperating fuel filter (new element), replaced the fuel pump, Checked the Yamaha fuel filter, Replaced the primer Bulb (Yamaha not Tempo), Had the carbs rebuilt, Set the timing according to the manual,<br />Then you may have luck by turning out the pilot jet screws (4 slotted head) 1 full turn from where they are now. It worked for my 86 Yamaha 115. Good Luck!

 

[Fully_Loaded1]

Re: 1984 yammy 115 rough idle

If the timing stop screw is loose and backed out this could be a problem. If you can get it to idle for a second try pulling the arm that is on the starboard side of the motor that goes almost up to the flywheel (it is grey and is held on by 1 14mm bolt) tword the front of the boat a little bit. If this helps or fixes it you will see the stop screw twords the top of it just tighen that so the timing arm does not go back as far. It only take the slightest bit of movement to make a noticable difference.

 

[Lasse Lehtonen]

Re: 1984 yammy 115 rough idle

I have the same problem with my yamaha 40 betol -91 autolube.It runs roughly between idle rpm and 2200 rpm, with higher speeds runs smoothly.Cooling is working normally and i have just changed all 3 sparkplugs but it didnt help.The autolube system is working normally I tested to disable it and run with 1:50 mixture but stil rough idle.What should I do now? I bought the boat and engine used 5 weeks ago.When engine is cold it runs smoother idle but stil not as smooth as is should.