Yamaha 15 hp 2 stroke--fuel issue

Jeff Reardon

Jeff Reardon

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I've got an older 15 hp Yamaha 2 stroke with a fuel issue. After running well all season, today it started not drawing fuel from the fuel tank. The motor would run perfectly and then suddenly stall out. If I pumped the bulb on the fuel line it would restart easily and run for a few minutes, then cut out again. This happened over and over again, and it seemed that the motor would run for a shorter period each time.

I'm no mechanic. Any suggestions for what might be wrong?
 
Thanks.

Any way to test this before I spring for a new fuel line? They are pretty pricy . . . . .
 
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Is the bulb staying hard? The line may be fine and your bulb may be going bad. I would also make sure your brass fittings in the tank are all tight and the hose is clamped to the fittings well. Also, not trying to be a smart ass but was the tank vented? I've been there done that.
 
As the other said...sounds like an air leak. Check all connections and make sure the primer bulb is staying firm....it could be just a bad primer bulb.

At the worst it sounds like it could also be the fuel pump, BUT that is not likely on that motor.

Would bet money that you have a line or bulb issue.
 
check your filter in the tank or filter on motor but when mine did that the jets were tarnished from not running it out of gas it only
took about a month for it to happen 100$ lesson learned i run it out of gas if im only going to let it set a week good luck
 
The tank was vented. (I did know to check that.)

I do use fuel stabilizer, and this is not acting like a fuel/water problem or anything similar. Engine runs fine until it runs out of gas, then restarts first pull when I pump the bulb back up.

Bulb is NOT staying hard.

Thanks for the thoughts. Sound like I should replace the bulb and fuel line and see if that fixes it.
 
IT sounds like it might be a fuel pump. If it were me find a friend that has a known good tank and fuel line see if the problems the same if it is. probably not the tank or the fuel line leading to the motor. Prime the ball and start your engine, make sure the ball gets hard before starting it, when the motor starts to stager try and squeeze the primer ball and see if it starts to run smooth again, if it does smooth out it is the fuel pump. Do a carb rebuild at the same time if it hasn't been done in awhile. Chris
 
IT sounds like it might be a fuel pump. If it were me find a friend that has a known good tank and fuel line see if the problems the same if it is. probably not the tank or the fuel line leading to the motor. Prime the ball and start your engine, make sure the ball gets hard before starting it, when the motor starts to stager try and squeeze the primer ball and see if it starts to run smooth again, if it does smooth out it is the fuel pump. Do a carb rebuild at the same time if it hasn't been done in awhile. Chris
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X2 if ya can keep the motor running by pumping the bulb, I'd go with a bad fuel pump. Ck. with NAPA auto parts, they have a good amout of OB motor parts& I know they are much cheeper than OMC for my old 6hp. rude. Thet have rebuild kits for some motors pumps too, if mechanicaly minded. Good luck!
Dennis
 
had the same problem with my honda. the o ring in the female connection going into the quikdisconnect was bad and leaking gas. fiqured this on my own after spending 200 dollars at the marine station to clean out the carb which was fine . told the guy did he run the motor for 25 minutes to check it out,no he didnt have that much time invoved. this after suppose he fixed it and I rowed back a mile.
 
Well you've already gotten a ton of input but I will add mine.
1st thought is air leak in the line or the bulb.
2nd is that your fuel pump has gone bad.
 
I now this is going to sound weird, trrying pumping the bulb when it is verticle, not horizontal. Sometimes those check valves don't work horizontally. See if you can prop the fuel line up so the bulb stays horizontal.

Mark W
 
had the same problem with my honda. the o ring in the female connection going into the quikdisconnect was bad and leaking gas. fiqured this on my own after spending 200 dollars at the marine station to clean out the carb which was fine . told the guy did he run the motor for 25 minutes to check it out,no he didnt have that much time invoved. this after suppose he fixed it and I rowed back a mile.First things first. Step by step before you drop a bunch of money. O rings are cheap start there. Then connectors to the bulb and end fittings, redo them. Once you know there isn't a air leak go on to some thing else.

First things first replace your O rings then your connectors to the bulb and ends of the line. Then go from there, do all the inexpensive things first.
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Thanks again, folks, helpful as always.

I talked to a good mechanic today who was quite helpful and confirmed what folks here have suggested--fuel pump or an air leak in the fuel hose.

(I also talked to two bad mechanics--one who is apparently in a urinating contest with Yamaha and now refuses to even discuss one, despite the fact that he's still listed as an official Yamaha dealer; another who wouldn't discuss anything about the motor with me until he'd done an evaluation, at a rate of $85/hr. This was after I told him I was ready to come down and purchase the parts from him.)

With some minimal coaching from the mechanic, I took the cover off the carburetor and took a look at the diaphragm underneath--he suggested I would see a hole if it was a fuel pump problem. The diaphragm looked fine to me.

I see a little bit of wear--cracking rubber on the surface--of the O ring at the motor end of the fuel line. I should also upgrade to a new ethanol-worthy fuel line and bulb, so I'll replace the whole shebang and see it that does it.

Thanks again for all the help, and wish me luck!

No stripers around this week anyway. I just heard from a guide up here who is VERY good that he and a client who is a good angler fished 7 days last week for 2 stripers. This is in a place where anyone with even basic local knowledge used to be able to count on multiple hook-ups on any decent tide.

We'd still like to get out for a boat ride though, and fall fishing and duck season are coming, so I hope this works.
 
If those fail check the pick-up tube inside the tank. I had the exact same problem and it turned out to be the plastic pick-up tube that runs to the bottom of the fuel tank had a hairline crack in it. When the tank was full it ran great but once it got low enough to exposed the crack it would begin to suck air and would not run without priming the bulb. Might be worth checking it out before going through the expense of a new fuel line.
 
If those fail check the pick-up tube inside the tank. I had the exact same problem and it turned out to be the plastic pick-up tube that runs to the bottom of the fuel tank had a hairline crack in it. When the tank was full it ran great but once it got low enough to exposed the crack it would begin to suck air and would not run without priming the bulb. Might be worth checking it out before going through the expense of a new fuel line.
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I agree with dpc. I had a similiar issue a few years back. I ended up unscrewing the pick up assembly from my tank and the pick up tube fell into the tank. I fixed it by adding a stainless hose clamp to keep the pick up tube attached.
 
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Replaced the fuel line, as it was time to upgrade for something ethanol-safe anyway. That did no fix the problem. Just got done replacing two diaphragms and two gaskets in the fuel pump assembly and will head out for a test drive in a few minutes.

I'm hoping it's not the tank, as new Yamaha fuel tanks are $105.
 
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