Need Some Help With 2 Stroke Outboard

[snguyen95]

I went out on the lake yesterday and I have a Yamaha 25hp 2 stroke. Well it took awhile to start which is wierd because it usually starts on the first pull even after it sits for a little bit. But then every time I put it in full open throttle it goes strong for a little bit then shuts off. Can anyone help me out? I have a feeling it might be the gas like the oils not mixed right or something.

[fishfordollars]

The mix won't have anything to do with it. It probably is in the fuel delivery system. Check the bulb to see if it is leaking down.

Could be anything including the fuel pump. If it is acting like it is running out of fuel you  just need to work your way through it. If it has a 6 gallon removable tank make sure it is vented. Check the fuel line, filters, and work your way through the system.

[Nitrofreak]

The mix won't have anything to do with it. It probably is in the fuel delivery system. Check the bulb to see if it is leaking down.

Could be anything including the fuel pump. If it is acting like it is running out of fuel you just need to work your way through it. If it has a 6 gallon removable tank make sure it is vented. Check the fuel line, filters, and work your way through the system.

x2 But I have a question or two.

When it shuts off is it like you reached over and turned the switch off or does it stumble and putter then die?

And when it does die, Does it start back up hard or easy or do you find yourself having to prime the fuel system again to get it started?

[snguyen95]

Ok thanks guys I'll check it later. But when it dies it starts slowing down then just shuts off like when you press the button. To start it back up it took around 10 pulls.

[fishfordollars]

Ok thanks guys I'll check it later. But when it dies it starts slowing down then just shuts off like when you press the button. To start it back up it took around 10 pulls.

Hate to throw this out there. Could it be trying to seize?

[bobbyc]

Does the boat sit for long periods? If so, you may need a stabilizer.

[cBooms@SML]

we have a 200hp yamaha 2 stroke. im not sure if you can idle it or not, but try idling it at a high rpm for a while, just to get the oil and gas through the system to kind of flush it i guess

[Way2slow]

If it was stalling from trying to seize, you would not immediately be able to pull the starter rope, you would have to wait several minutes for pistons to cool and shrink before they would be free enough to let you pull the rope again, or if electric start, before the starter can turn it over again.

Sounds like a classic fuel delivery problem.  Keep pumping the primer bulb by hand as you're running.  If it stays running then, you may have a bad fuel pump.  You could also have a needle/seat sticking and not letting enough fuel into the bowl.   Also, pull the cover off and pump the primer bulb firm, then hold pressure on it and see if you see any leaks in any fuel lines.  If they leak gas, they can suck air.  When it dies, is the primer bulb sucked in, if so you have a restriction at the tank.   May need the carbs cleaned, may need a fuel pump, may have a leak or restriction.  You just have to go through the steps of elemination to isolate the problem.

[CAdeltaLipRipper]

Cause its not a mercury  ;D

[Way2slow]

If it was a Mercury 25, depending on year, no telling who made it, you can bet it probably was not "Mercury".  I don't think they make anything below 30hp.  I think Tohatsu made them for a long time and still makes them, they just paint them black for Mercury and put Merc's decals on them.  Even on the bigger motors, good chance Mercury didn't make the power heads.  Yamaha used to build a lot of them and may still do. 

So, when you bragg about your merc, it's probably somebody elses motor you're bragging about.

[South FLA]

If it was a Mercury 25, depending on year, no telling who made it, you can bet it probably was not "Mercury". I don't think they make anything below 30hp. I think Tohatsu made them for a long time and still makes them, they just paint them black for Mercury and put Merc's decals on them. Even on the bigger motors, good chance Mercury didn't make the power heads. Yamaha used to build a lot of them and may still do.

So, when you bragg about your merc, it's probably somebody elses motor you're bragging about.

I know for a fact the Yamaha use to build smaller engines for Merc, so if you are plugging Merc might as well say good job Yammy! 

I have a 1998 Evinrude that would always start and had a hard time starting after sitting a bit, turned out to be water in the fuel.  I would get some fresh fuel and use max dosage of Sea Foam and run the motor for a bit around the lake at WOT.