2006 50HP 2 stroke fuel problem?

[Elkins45]

I’m having a sudden problem with what was a perfectly running engine the last time it ran a month ago. It’s somewhat similar to the one described in this thread: https://forums.iboats.com/forum/eng...rustrating-yamaha-50-hp-2-stroke-problem-help

I dropped the lower unit and replaced the impeller as a preventative maintainance item. This is the first time it has been run since then. It started fine but it is shuddering and dying when I try to smoothly take it past about 1500 rpm. It has no problem accelerating and running when using the fast idle lever, and I can jam the gear lever all the way forward and it will spin up and go. Once I get past the 1500-2000 rpm bump it has no trouble running at normal full forward speed.

This wasn’t a gradual problem: it just appeared today. I took the cowl off once it was back on the trailer and couldn’t find anything obviously amiss.

Suggestions are welcome. Again, it’s a 2006 oil-injected two stroke.

 

[Elkins45]

So a bottle of Seafoam helped a little, and as long as I pay attention I can accelerate past the “dead spot” without killing it. Obviously something is clogged in the carbs.

How hard are the carbs to remove and replace on these motors? I’ve done it on a 25hp four stroke, but not this motor with multiple carbs. I might just take them off and give them a good cleaning if it doesn’t involve some delicate and potentially damaging procedures or required specials tools and skills.

 

[Sea Rider]

Is the automatic, manual choke working smoothly. That's closing the butterfly when priming engine and releasing it when started. Have seen cases where solenoid or butterfly rod got stuck half way and engine missed. Close, release solenoid with finger and check if closes and opens fully without restriction, align solenoid plunger or lube butterfly rod to work smoothly and properly if that's the failure culprit.

Happy Boating

 

[99yam40]

you really need to find a service manual for your motor and follow the link and sync procedure every time after cleaning and re installing the carbs

 

[Elkins45]

Is the automatic, manual choke working smoothly. That's closing the butterfly when priming engine and releasing it when started. Have seen cases where solenoid or butterfly rod got stuck half way and engine missed. Close, release solenoid with finger and check if closes and opens fully without restriction, align solenoid plunger or lube butterfly rod to work smoothly and properly if that's the failure culprit.

Happy Boating

This motor doesn’t have a conventional choke. It has the Primestart system.

 

[stevenmurray1987]

I used this video when I cleaned carbs for the first time.

https://www.youtube.com/watch?v=iPcwFREbUPE

It took a couple hours and was not too complicated. I found congealed gas clogging a big jet.

 

[Elkins45]

I used this video when I cleaned carbs for the first time.

https://www.youtube.com/watch?v=iPcwFREbUPE

It took a couple hours and was not too complicated. I found congealed gas clogging a big jet.

Thanks, I will watch the video. When I cleaned the carb on my 25 hp four stroke I found a whole bunch of congealed gas even though the motor had been run just a month before. People talk about winterizing their boats, but I think letting it bake in the summer sun is worse because the heat causes the volatiles to boil off and bad stuff to happen much faster. That carb was crazy complex with a whole bunch of little passages that were gelled up. I suspect that’s what’s happened here, just not to the same degree.

I wish this motor had a conventional choke. On my old Johnson you could just run it up to full speed and close the choke to unstick a whole bunch of problems before they got too bad. I might take off the breather cover and give it a good “hillbilly choking” with a clean towel to see if I can emulate the same thing.

 

[lerobert]

I had this same problem with a 50tlrb made me crazy for months. there's a red lever on the #2 carb with three settings run emergency and closed. set this lever to closed after your motor warms up and see if the problem goes away. if it does then you have an issue with the prime start assembly. you can test it with a meter as it is an electrothermal valve. if it is not functioning then all three carbs are getting extra fuel all the time making your mixture always too rich. that e-valve is mounted to a a small fuel pump(part of the #2 carb assembly) which supplies the extra fuel for start-up. when the motor is running that e-valve recieves 12v current from the motor causing it to heat up and close the valve over a short period of time. Apparently it can fail in either the open or closed position, but fear not you can manually over ride with the red lever or just replace. it is easy to R&R but it's around $200 for the part