2001 70hp Yamaha 2 stroke stalls at high RPM's

My engine will run fine at low rpm's and will run 50% of the time at full throttle, but some of the time when I open it up, it stalls out, as if it were running out of fuel. After that happens I can restart it and run it at low rpm's. I can rev it up to high rpm's in neutral. Then after a while, once I shut it down and restart it, it will run fine again. Any suggestions? Please help.

Also after the engine stalls out, I need to re-prime in order to restart the engine.

check the fuel tank vent.also could be the fuel pump not pumping.pull it to bits if you can and check for any dirt,you should be able to blow thru it,but not suck back.must admit my 3cyl 30hp 1992 does similar things,seems to starve at full throttle.tried all sorts.

look for cracked vacum lines or lines that may have fallen off. had a problem kinda like that and found a 1/8" line fall off the fuel pump could not see it untill i got in a ways

Thanks guys, have a new fuel line on the tank, but worried it might be leaking air. Going to try a different line on a clean tank and see if that works, if so - I'll switch out the other. Going to look all through it and see if it might be getting air in anywhere or if any lines have fallen off, check fuel pump, etc.

I am also going to see if it might be an issue with the ignition switch, initially the kill switch needed to be jiggled in order for the engine to start up, I checked all the wiring and it wasn't that, so I may need to replace the switch.

Any other ideas or suggestions before pulling off the carbs and cleaning them - if those don't work? Thanks for the help, I'll let you know how it goes this afternoon.

Pulling and cleaning the carbs is pretty easy on these (just did mine last weekend). Just make sure you don't get any carb cleaner (berkebile 2+2 gum cutter is my favorite with compressed air) on the rubber orings or they swell up.

Hi, Greg here. I have the exact problem with mine too. Just when you think it's going to plane out, the motor begins to hesitate and then eventually dies. It restarts every time and revs up in neutral but as soon as I put it under load, it starts to chug again. If you run it at half speed, you can usually maintain that speed but as soon as you go full out, it'll go for about 40 seconds and then lose power and die out again. My neighbour tells me to replace the plugs regardless of what they look like so I will. So far, checked the carbs (clean as a whistle), cleaned the fuel strainer and replaced the fuel hose from the tank to the motor (factory Yamaha line $$$$) This includes both fittings and the primer ball.
The fuel is new and the oil in injecting..............I will be a happy guy when a solution is found. Please let me know if you get to the bottom of it and I'll do the same. Mine is a 1990 2 stroke 70 hp. A little older but what they hey

maybe a can help, lets start by trying a different fuel tank remove fuel connectors place line directly in fuel tank connect directly to fuel filter at motor. remove clear bowl engine fuel filter ther should be a black o ring in top lip of filter bowl. push in choke while running under load does motor speed up if yes lean on fuel. modles with butterfly choke run under load with breather off make shure choke shutters are not sucking shut. as for the engine that shuts down and restarts after sitting you my not have a fuel problem your motor my be going into guardian.over heat/bad float snd in oil tank. has the warring buzzer been verified if your warning horn is bad one of thes conditions may be your problem without you knowing.when the motor experences one of these conditions you will have to turn off key to reset only then will you be able throttle past idle.as for possible ign switch this can be checked by simply unpluging larg black cannon connector located inside engine pan after motor has been started run boat normanly if problem goes away key and kill switch need inspecting.you will have to reconnect engine harness to shut down motor. good luck guys let us know what you find

hello i know this forum is extremely old.. I'm Curious to know if anyone ever found out the issue. mY1990 yamaha outboard 85 2 stroe cuts off at high rpms. I've cleaned the carbs, replace fuel pump, clean fuel filter, replace spark plugs.. next is to replace fuel lines and choke pump. it seems to be lacking proper fuel at high rpms, or not retaining feul. what do you guys suggest i do next? thanks in advanced.

Yamahascboy,you will get a better response if you post a new thread, Try using a timing light while running to see if you are losing spark, use an assistant.

Hi there
I have a very similar problem I have a saltwater series 2 “ 225 outboard Yamaha
First off I’d like to give Yamaha a shout out about how unbelievablely reliable It has been for us , it has never missed a beat in 23years it has been service only once last year due to its cooling system corroding (blades on the pump corroded causing slower water flow when running engine to hard causing it to overheat it’ll go into like a limpmode
#now I have a problem which is
In & out of the water -
It starts perfectly
Idiols perfect engine sounds spot on
accelerates to about a quarter of the power when the engine is cold / first 15 min it’ll get up & plane at between a quarter & just over
If I give a bit extra acceleration it’ll stall or if I hit some chop from other boats wake it’ll stall out & it will start fine & get back up to the quarter mark again
The other thing I noticed is it seems to get worse ,the longer I’m running the engine the acceleration point of stalling gets less & less

I have replaced the fuel filter that filters the water the clear bulb had some brown rusty looking water in there & the filter was A bit rusty that’s all new
if anyone knows about Yamaha engines I would appreciate your HELP thx