Diagnosing Fuel Issue for Yamaha 2 Stroke 115 hp

[@sargemarine3709]

Same problem with this same year, and it's a 115 ! Thank you !

[@emilbraunlich1928]

I had theexact same problem with my mercury it would die when I gave it more throttle. I diagnosed it when I had my friend pump the priming bulb when i was at full throttle and it worked 100%. Now to fix the problem i found was replace the check valves on your fuel pump. They go bad and rot with the ethanol and leak fuel back to the suction side of the pump and not discharge the full amount of fuel to the discharge. I still havnt fully got my engine to 100% because I only replaced 1 pump with 2 on the side but it was a significant change with just 1 pump new. Hope this may help with your troubleshooting with a safe boating season

[@NinetyOneAdventures]

I replaced mine with an after market fuel pump from Amazon and the diaphragm in the new pump ended up being bad sending me on a wild goose chase. Along with other micro problems like a new primer bulb that wasn't any good. I then ordered all Yamaha products and had much better luck. Thanks for replying and trying to help. It's greatly appreciated!

[@Gigglepoops85]

Same problem in my yamaha 115. It would surge at higher rpms. Then struggle to just get up on plain. Disconnected right from the gas tank and put the fuel line straight into a portable gas tank and it ran like a top. Took apart the gas tank thought I found a crack in the pickup tube. Nope. Put it all back together and couldnt get it started. Picking up the struggle from last year today. Have you fully fixed your issue? I've had the fuel pump replaced carbs redone and taken apart the whole fuel system. Replacing the primer bulb today.

[@DeaconFowler]

this is an old video but hoping for response.. rebuilt mine 99 c115txrx and the dang bowl gaskets touch the floats and keep the needles from seating. had to hand cut them. still trouble shooting my lower carb. when pumping the bulb the lower pukes for a second then the needles seat. any ideas on rebuild things to watch. please let me know.

[@NinetyOneAdventures]

Hi DeaconFlower If the gasket is touching the floats and not allowing the needle to seat right away it seems you would get a little fuel to leak by before you had enough pressure in the bowl to force the float past the gasket. You should be able to order the oem gaskets from boats.net.

[@mikelaplante7873]

That sounds like the gray fuel line sickness my bass boat had. Was frustrating until I figured it out.

[@NinetyOneAdventures]

Yea.. I replaced all the fuel lines and everything. The problem was I replaced everything so I'm not sure which one was the culprit. I believe it was the fuel pump.

[@wanesweb]

I am having same problem with the same motor 1999 and i noticed you have gray fuel lines i saw a video where the guy said the gray lines have a film that gunks up the lines cause of ethanol

[@tonybruno7848]

That grey fuel line ain't worth a crap. At the dealership where I work we automatically change it to good black fuel line.

[@AceInvests]

just got my 1997 cobia 194 with a 115 yamaha 115hp and jesus christ i need some help. any manuals ???? i need to change my fuel sender pump

[@Mitoa]

I have a 17” cobia from 97, how you liking it? I use a gas tank on my deck, is your internal tank still good?

[@adammccoy8479]

I got a boat with the same motor but the ‘85 version. It was doing the same thing and found it was a faulty disconnect where the fuel line connects to the motor. Sometimes it would work fine and then it would loosen slightly and partially close the little ball valve in there where it would restrict fuel flow and get enough fuel to idle or at low throttle, but die out when throttled up, or sometimes it would cut off flow altogether. Replaced that disconnect and has run great ever since.

[@NinetyOneAdventures]

If you look in the description we've got a couple more videos where we cover the issues. All is well with the boat now! So happy she's running beautifully! Thanks for watching and commenting friend.

[@cynthiadaw131]

Help me somebody!! I have Johnson 150 ocean pro 2 stroke 1999. I can go out and run boat for about a mile. Then it starts running raggady. It'll stay that way untill 4 or 5 hours or next morning. Same thing runs idols good but after planning out and running about 25mph or so. About a mile then it starts running raggady again. It does good for a mile maybe but it want run right until next morning again. What could be doing this? Qny suggestions?

[@NinetyOneAdventures]

It could be anything. It could be that the fuel tank has trash in it. Go to AutoZone pick up a fuel pressure gage that reads both pressure and vacuum. Check if you have vacuum between the fuel pump towards the fuel tank. Check to see if you have pressure between the fuel tank and carbs. If I remember correctly it should be somewhere in between 5 and 8 pounds of pressure. And you'll probably have to go run the boat and let the problem start then bring it back to the ramp and check it. That will tell you if your problem is before or after the fuel pump. The fuel pump is a serviceable item and you may want to replace it. It could be anywhere from trash in the carb bowls, trash in fuel tank, dirty fuel filter or bad primer ball. There may be a check valve where the fuel line connects to the boat motor and if you have a internal tank there may be a check valve on top of the pick up tube that may be gummed up.

[@bobbyinso9752]

Hi hello sir have you experience Yamaha 115 HP when you running full speed can't how to fix please my Yamaha 115hp 2stoke

[@NinetyOneAdventures]

Not sure I understand the problem. I need more details

[@MrTomtusti]

is that outboard oil injected ? I just got 1 96' 115 Yamaha , no oil tank under the hood , no oil line feed or oil /gas blend pump

[@NinetyOneAdventures]

No it is premixed

[@MrTomtusti]

Some of these Yamahas come this way in the '90s? Or has the oil injection been deleted? If someone deleted the one on mine they did a great job there's no trace of anything

[@NinetyOneAdventures]

@@MrTomtusti I'm not sure what models came with oil injection. If you go to boats.net and look up your model by serial/model# you should be able to see if your motor came with it or not. They should have a complete parts explosion on you motor upper and lower unit.

[@MrTomtusti]

@@NinetyOneAdventures Seems strange that some would / would not have oil injection. Most every Yamaha snowmobile and motorcycle had it from the 1960's up

[@SUNNY-BANDZ]

I also have a 98 115 I’m having the same issues, my motor would run fine at idle through half throttle but when I tried to get on plane it would sputter until one of my homies would pump the bulb about 3 times then it would roll fine . Took it in replaced the water fuel separator replaced the line from the tank to the water fuel separator changed the primer bulb and the lines from that to the motor Still nothing changed the fuel pump nothing . The motor runs for a little while like a minute top then shuts off the bulb doesn’t stay primed either , like it’s not pulling a constant suction of fuel does anyone have any ideas? At this moment I’m trying to remove my pick up line to see if it’s clogged/cracked anything will help thank you!

[@NinetyOneAdventures]

Your pickup line should have a check ball on top. Make sure the ball inside the check valve is able to move freely. There's also another check valve right where the fuel line meets the motor housing on the outside and picks back up to the fuel line on the inside. Between the 2 lines fun the outside and the inside there should be another check valve with a ball in it. These are too keep the fuel from going back into the tank and the system primed. The balls can get gummed up or rusted and don't move freely to allow fuel to pass. You should also have another fuel filter bolted on the side of the motor next to your fuel pump. You mentioned you replaced the fuel pump. I had trouble with after market fuel pumps and had better results with OEM parts. You can buy a cheap fuel pressure gage at any auto parts store and check the fuel pressure after the fuel pump to see if you have 4 to 7 psi to see if the fuel pump is pushing fuel. You can also check before the fuel pump to see if the fuel pump is pulling vacuum. If you have good fuel pressure and vacuum thru higher rpm then your floats may be stuck in the bowls of the carburetors. When you pump the primer ball it's forcing the fuel pass the system and filling your bowls. It might not be a bad idea to pull your carbs and clean them up. There are several videos that should help.

[@SUNNY-BANDZ]

Sorry for the late answer but i ended up replacing everything besides the carbs dealing with fuel and it started to work with slight surging only at idle only had a little gas left after messing with it all day so just put a bit of sea foam in it and it definitely helped it out so tomorrow I think I’m going to put a good bit of fuel with a nice sea foam mixture and go take it out and see how it goes. If I still end up having problems my next move will be a carb clean, I really appreciate the answer and insight. Also it bothers me that I don’t know exactly what was causing the problem😂

[@NinetyOneAdventures]

@@SUNNY-BANDZ keep me updated! Good luck!

[@jordannuttall9562]

Great helpful video man, I am having problems with the same outboard now if you could offer some advice please? You seem to really know your stuff

[@NinetyOneAdventures]

I would start with the maintenence items first. Make sure your have good clean fuel filters. Replace the fuel pump. And see what happens.

[@NinetyOneAdventures]

And primer bulb

[@davidjessee7701]

Nice fab on the float perch..... I have the carbs on my 98 130hp .... The top carb is flooding on the right side.... Ive had the carb on and off 20 times... For some reason the needle isn't shutting off rhe fuel... Squeeze the bulb and it runs out the emulsion tube.. When its running , fuel runs out the emulsion tube..ive polished the seats installed new needles, ajusted the floats. And still the top right carb pours fuel .... The only way it will not pour fuel is when I adjust the float so low that fuel won't even come in the carb... Wich then will lean out the cylinder to it will definitely damage the motor... I can't find anything wrong with it....turn it upside down and blow in the fuel inlet and the needles are closed..but when I turn it over and attach the fuel line squeeze the bulb , fuel runs out of the emulsion tube...ugh...😒

[@NinetyOneAdventures]

Sometimes the float can have a crack in them. Pull the float back out and shake it to see if you can hear gas inside or you can also pour gas in a bowl and put the float in and add a weight on top of the float to keep in submersed and let it set overnight to see if it fills up with gas. Also when you put the carbs back on the engine make sure the butterflies are synched. Because one carb will be richer than the other.

[@rkanlaya]

I would use J&B weld. It works on my yamaha 60 hp

[@samtate1260]

Those gray hoses break down from today’s gasoline and fragments of the inside of the gray hose will go into the carburetor constantly get rid of those gray hoses and use black ones for fuel

[@NinetyOneAdventures]

I agree with that because I'm sure those were the original fuel lines. And I'm sure ethanol broke the lines down over the years. I did end up replacing all the fuel lines from the fuel tank all the way to the carbs.

[@richardgeeslin9472]

Todd, never run that engine with ethanol gas, always...always use Yamaha Ring Free in the gas per directions!

[@NinetyOneAdventures]

Can you tell me more about it?

[@richardgeeslin9472]

@@NinetyOneAdventures I have the exact same boat and Yamaha 115, 1999 2 stroke. Have NEVER used ethanol gas and have used the Yamaha product Ring Free since day one, which is a fuel additive, not cheap, sold only at Yamaha dealers or on line, it keeps the engine components and the fuel system clean. Don't be suckered in by some of the snake oils some companies are selling. I had to have my fuel tank pumped once, got bad gas with lots of water. You have an access panel to the fuel tank and sending unit under the seat. Pull out the sending unit and pump ALL of the gas out of the tank completely. Try that approach. A couple of times I've removed the carb covers and sprayed a can of Sea Foam with a spray bottle directly into the carbs with the engine running at about 1000 rpm, lots of smoke, didn't hurt.

[@brycealkins1529]

Or just use ethanol free gas

[@harveynewman4333]

you could put the older carbs on it with no problem. just be sure you dont put the 6L100 series carbs from the 130 on it. stay with 6E 500 series carbs.

[@NinetyOneAdventures]

I found the original carbs on boat.net but I was able to fab a float perch. I got lucky and didn't need to purchase new carbs! Thanks for the tip though!

[@harveynewman4333]

@@NinetyOneAdventures welcome

[@superdutyf450]

will never work properly and won't last a month even if float height is correct, no epoxy no glue no matter what will last in bowl of carb period, there was an easier softer way to fix all the different problems the outboard had but that was couple years ago, you did it obviously and that's better than most bud but outboards or engines I. general don't like your Jerry riggin or anyone's for that matter antisiphpn valve failure in near future I imagine, anyway. 33yrs 2 diff manufacturers and alot of training and hard knock repair orders I've seen it all but rank your in top 25 brother good luck and godbless

[@NinetyOneAdventures]

I appreciate the kind words. Everything held together and worked great. 👍