95' Yamaha V4 115 2 stroke , carb fuel mixture settings?

[wmc]

I, have a yamaha 115 outboard, its on an 18' hydra sport has a 13x19 prop, it runs somewhat good when I, got it, but seemed to be a little slugglish as the original seller said he had the carbs rebuilt, it appears to have two duplex type of carbs with adjustment screws on each side of the carbs, I, checked the setting on the mixture screws and there 3 1/2 turns out on the STB side and 2 1/4 turns on the PS side, upper and lowers equal, the engine runs ok at idle but seems to dog down going from idle to mid throttle then it recovers and runs up to 5500 rpms its just in the lower and mid range that is has the power loss, or when you try a hole shot, I'm an ok car mechanic but not to sure yet with outboards, and need some input on the fuel screw turns, Thanks any help greatly appreciated.

 

[Capt Ken]

Re: 95' Yamaha V4 115 2 stroke , carb fuel mixture settings?

The book will say the screws should be 5/8 - 1 turn but normally the older ones will be closer to 1.5 turns. 3.5 is too much. I would be checking my float levels and low speed jets

 

[wmc]

Re: 95' Yamaha V4 115 2 stroke , carb fuel mixture settings?

Thanks, at least this is a starting point, I, suspect 1 1/5 at most, but are they the same on both sides of the carbs? as there is 4 screws

 

[Capt Ken]

Re: 95' Yamaha V4 115 2 stroke , carb fuel mixture settings?

You have to adjust by ear. When they sneeze, it's too lean and back each out till it quits sneezing.

 

[wmc]

Re: 95' Yamaha V4 115 2 stroke , carb fuel mixture settings?

Thanks for the help on this, going to hunt down a service manual for future use, I, just completely broke the carbs down cleaned them to make sure dirt is not the issue,checked float levels there good, around .620 upside down method, fuel pump good also, reasembled and it started right up and coughed and sneezed and back fired like crazy for 5 minutes, I, kept backing the screws out, smoothed out at 2 1/5 almost 3 turns each seems kind of far but it woulnt run below that, not sure what is going on with that?

 

[Bamaman1]

Re: 95' Yamaha V4 115 2 stroke , carb fuel mixture settings?

You might want to take it to an experienced marine mechanic to get him to check out timing and then tune the carbs. Should be a one hour job.

 

[wmc]

Re: 95' Yamaha V4 115 2 stroke , carb fuel mixture settings?

Bamaman1 normally I, would do just that, but Actually, I'm an ASE certified mechanic on auto and truck engines, so I, knew I, could figure this out, so I, did a lot of reading and learning on boat engines, the basic principals are the same, as a matter of fact I, just did what you suggested about the timing and it was the whole problem all along 6degrees to far at idle and about 4degrees to far at WOT according to the factory specs, then discovered the carb's were not in sync with the timing advance, so take mine and bamaman1's advice to anyone chasing there tail on carb cleaning and fuel changes and over with no success, "check the timing also!"

 

[wmc]

Re: 95' Yamaha V4 115 2 stroke , carb fuel mixture settings?

I, hope this helps anyone that may need some simple to follow timing directions