Yamaha 50 still wont run

[caymanscott]

Greetings fellow triumph owners-I wrote a couple of weeks ago regarding my triumph 150 with the yamaha 50 2 stoke that kept dying(usually way out in the ocean)-had lots of replies, and have tried a few things, but it still wont run right-itmay run fine for a while ( until it warms up?) and then it stalls when throttled back-I can re start it and it runs for a few seconds and dies-I can keep it running by throttling up without engaging the prop, and it revs freely, but as soon as I put it in gear it stalls-to date we have changed the plugs, checked ignition components and had the carbs off to inspect and clean the jets, float valves and all aspects of the fuel supply system. I replaced the fuel, added stabilizer (although not Star-tron-cant get it here), added another water/fuel seperator-darndest thing and its only got 29 hours on it-even the mechanic is saying things like "sure doesnt run like a Honda" or"time for a new engine"-any other ideas-thanking you in advance.-Scott in Cayman

[cagrove]

Originally Posted by caymanscott

-even the mechanic is saying things like "sure doesnt run like a Honda" or"time for a new engine"-any other ideas-thanking you in advance.-Scott in Cayman

Scott,
I'm sorry I can't help you with your problem...that's got to be very frustrating. However, my thinking is this...we have lawyers for legal problems and doctors for medical issues. We have marine mechanics to fix our motors when they don't function properly. If I had a medical issue that my doctor didn't know how to address, I would find a new doctor. If you have a mechanic that doesn't know how to fix your motor, you need to find a new mechanic. There is obviously something wrong, a good mechanic will not give up until he finds the problem. There are only a limited number of things that it could be.

Having said that, I once had an older Evinrude that acted very close to what you described. It turned out to be several things contributing to the problem...old gas, dirt in the gas tank, dirty carbs, and a crack around the primer bulb in the fuel line. It sounds like you've addressed all of the fuel issues. Just brainstorming here but you may want to check: (1) timing; (2)there's nothing pinching the fuel line (esp. when engaging the gears)(3) cracks in the fuel line and/or primer bulb.

Again, I'm not a mechanic...I blow stuff up for a living. Let me know if you need a couple of sticks of dynamite if nothing else works.

Good luck.

[caymanscott]

Hi-thanks for the response and believe me , I have tried, but mechanics here are not plentiful and especially qualified ones-even to work on your car-we are going to try a few more things and then if that doesnt work, I will be back in touch for some C4 or something!

[saltydawg]

sounds like a problem I had with a mercury several years ago, have you done a compression test on all of the cylinders? I had blown rings and the motor would run until it heated up and the metal expanded and it acted alot like I understand your problem is especially when you put it into gear.

[McSpadden]

Scott,

I had a Yamaha 25 that acted identical to what you are describing. I had taken the carb off at least 4 times and cleaned but on the 5th time I removed a rubber plug, found another spot that needed cleaning and after getting the gunk out the motor ran fine up until I sold the boat it was on. Don't remember the exact location of the plug but recommend you look one more time and remove any plugs you do find. Then if there is a needle or anything underneath take it out and give it a good cleaning.

Hope this helps, sure sounds like what I experienced.

Dave

[BigBird]

All of the above and a couple of more things. Ensure your fuel line bulb is pumped up tight while running. One hook in the gas line will cach air without leaking.
Fyi, after solving your problem-My Yamaha 40 on my older skiff has run great for 10 years, however is oil sensitive. It wont idle properly with cheap oil. I run only Yamalube or quicksilver. Ididnt believe it but made drastic difference and all my idle issues went away.

[Whitto]

Hi Scott,

Just like everyone else ... your problem sounds like what happened to me!

I had a new 25hp 2stroke motor and it worked fine for a little while ... then it would die and fart around trying to start and then suddenly it would fire up and run great for a while, then it would die and fart around trying to start and ... well you know.

The problem turned out to be a split in the fuel pickup within the gas tank ... when the tank was full or in choppy water the motor worked very well ... if we sat and fished for a while it would start and then would die at odd times.

Hope you find the problem soon, good hunting!

[BarryB]

Hi Scott,

I have a Yamaha 70 2 stroke. I purchased the service manual from yamaha for reference. In the trouble analysis chapter under the heading of "Engine Stalls" The fuel system is the prime suspect.

If you can find a clean, portable fuel tank with fuel line, I'd try that first with fresh fuel. Just putt around inland to see if the motor stalls.

The secondary suspect according to the book is electrical, either the ignition coil or the CDI unit. Perhaps, when either gets hot, the internal wiring shorts out. Try running the engine without the cowling in calm water near shore.

When you are done with these test, fill us in on the results.