yamaha 115 1990 model

[Bill A]

Just bought a boat with a Yamaha 115 and can't get it to idle unless I adjust the air screws to most of the way out. The manual says they're supposed to be seated then backed out 5/8 of a turn. I'm way past that, but any less and the engine won't idle unless I choke it. I also have trouble getting it to start with any less. Do I need to be doing some more cleaning? I just took them apart and cleaned them.

The engine runs fine at top end.

Thanks Bill A.

[Ken]

Bill,
Sounds like low speed jets are clogged.
Try removing the pilot screws and squirting some Berryman's Chemtool into the orifices.
Or try a shock treatment with SeaFoam or RingFree - sometimes this cleans the carbs enough to get by.
Otherwise, gonna have to tear down those carbs again and remove all jets and clean.
Good luck [img]smile.gif[/img] ,
Ken K

[Bill A]

Thanks Ken,

One other question if you don't mind. I installed one of those RACOR filters. Does that restrict fuel flow at low speed?

[jb123]

Will only restrict if fully clogged..they will rust out before they clog.

[Ken]

Bill,
Depends on which fuel filter you installed.
I assume you are talking about one of the larger ones rated at 60 gph, right? Won't be a problem until it clogs, like "jb" says.
Racor does make a small one rated for small outboards that might give you some fuel flow resistance at higher rpm.
Good luck [img]smile.gif[/img] ,
Ken K

[yamaha-115-96]

Hi!

I have just the same probs as you.

Posted this at another marine engine forum:

Hallo, I have recently had the same probs. Could barely take down my Yamaha 115hp, -96 to lowest idle and finally died when kicking in the gear. The probs started in april and then took it to repair shop. Guy there said it was spark plugs and a dried fuel line. Got the same symptom some week ago. Repairman frustrated when I told him he hadn't fixed the problem. Ordered a Pro Manual CD from eBay. Adjusted the low left carburetor screw. It was particulary sensitive and the spring seemed to be fully extended when i found the optimal position (the engine not stopping !!). I put a spacerbetween the screw head and the spring and it seems it sits stable there. have to go through the carburetors after the season.

I have now adjusted up the idle a little and runs smooth.

This motor has some quirks.

1. The guy i bought it from said there was just a manual choke but i didcovered a magneto coil pulling it. just don't know which wire to attach it to some switch near to driving place. The maneuver box doesn't seem to have a choke knob !!!

2. It has no remote oiltank but just a plastic bottle with a primer ball equiped oiltube.

Can you manufacture such a tank yourself with sensor and pump??? An other option is to place the tank at the level of the internal oiltank and connect it by means of a siphon. Is it possible??

3. The boat was delivered with a LCD-gauge showing speed, trip, time. Two petrol-pump symbols, one temperature symbol and a bettery symbol. Also a PTT-level gauge.

On the back it has a blue and black pair of wires and a centre placed 8 pole wire divisioned into a white, white/blue and black bundling. Also a pink, yellow and black bundling with an additional grey cable.

There is also a ~4mm black plastic tube with a 1mm hole protruding from the back. Should there be attached some pressure log/speed tube???

there is one isolated yellow wire sticking out from the main electric in/out bundle. Also a black/red, black, blue and grey? attached to a square contact, sitting loose. One three wire "trailer switch" contact. (What is trailer switch???)

Apart from the main bundel there is also a green, yellow, red/yellow, red/green square contact connected to a black, grey, orange, pink square connector.

Does this all make any sense. Thankful for any input!!

Regards!