Yamaha 50 TLR---Stalls on the hose?

[Steve762us]

I just purchased a used 2007 150, with a Yamaha 50 2-stroke motor. I'm new to working with outboards, but I've used the earmuff style flush attachments, and know to start the water before the motor...

The engine has run perfectly on the water for me, but the last time I flushed it, it stalled a couple of times, for no apparent reason. I was able to re-start it promptly, and finished the flush after about ten minutes (the manual says 15, but seems like ten would be adequate).

I ran the boat about twenty five miles last nite, with several stops & starts...no problems. I went to flush her this afternoon; pumped the bulb up, and she started fine. After about two minutes, the engine stalled out, and I couldn't get her to re-start. The primer bulb was soft, and I pumped it back up but still couldn't get the engine to re-start.

Fuel is fine, and should be fresh; I've put about ten hours on the motor since purchasing it about two weeks ago. Everytime I've gone to re-start it on the water, it's fired right up...and it hasn't stalled on the water...

Any suggestions on things to check would be appreciated.

[NCangler]

Steve, I'm sure you've already thought of this but I've done it myself so it is the starting point in a checklist...be sure the kill switch clip is connected. Not sure about that engine but you may also need to do a reset sequence if it cuts off when it is time to be serviced.

[Steve762us]

Originally Posted by NCangler

Steve, I'm sure you've already thought of this but I've done it myself so it is the starting point in a checklist...be sure the kill switch clip is connected. Not sure about that engine but you may also need to do a reset sequence if it cuts off when it is time to be serviced.

Yes, I did check stop clip...it was in position when the engine stalled. I didn't mention it in the original post, but I pulled it and re-seated it just to be sure, and still couldn't get it to restart.

[BarryB]

Hi Steve,

I flush my 2 stroke Yamaha 70 the same way, never a problem. However, my motor only has 60 hours on it so far.

1. Did you run the motor at idle (same amount of time) in the water the same as when you flush the motor?

If not, try that. If you have the same problem, I would check the carbs or fuel pump.

2. Is the motor tilted different when you flush it vs. when your on the water?

If so, possible problem with the float system in the carbs.

3. Have you pulled the spark plugs?

If the plug tip and insulator is black, the motor may be running a bit too rich at idle.

[Steve762us]

Originally Posted by BarryB

Hi Steve,

I flush my 2 stroke Yamaha 70 the same way, never a problem. However, my motor only has 60 hours on it so far.

1. Did you run the motor at idle (same amount of time) in the water the same as when you flush the motor?

If not, try that. If you have the same problem, I would check the carbs or fuel pump.

Nope...in the water, I'm usually moving along, 3800 RPMs or so...no occasion for
idling, with what I'm doing.

2. Is the motor tilted different when you flush it vs. when your on the water?

No, she's basically "up & down" vertical...not in the travel-tilt lock mode, during flushing.

If so, possible problem with the float system in the carbs.

3. Have you pulled the spark plugs?

If the plug tip and insulator is black, the motor may be running a bit too rich at idle.

No, I haven't pulled the plugs...I can do that. Is idle mix adjustable, on these?

My motor only has 53 hours on it, Barry...shows June 06 on the sticker.

[BarryB]

Hi Steve,

Recreate the problem. With the boat in the water, let it idle for 10 minutes, if the engine quits, at least you know it's not a flushing problem.

It sounds like a carb. problem.

You can order the Yamaha repair manual. It runs about $80 with shipping, or try to find one on eBay.

On my 70, there is a procedure to set the idle speed and mixture for all three carbs. There is probably one for your motor too. If you are going to tinker, you need a book.

[Steve762us]

...with these motors, is it possible to have *too much pressure* on the hose, supplying the coolant water flow---to the point it could back up thru exhaust to the cylinders?

I've probably had a pretty healthy water pressure at the muffs...

[Lucky]

Originally Posted by Steve762us

...with these motors, is it possible to have *too much pressure* on the hose, supplying the coolant water flow---to the point it could back up thru exhaust to the cylinders?

Not possible, unless you have a clog in your exhaust... but then the engine wouldn't run at all.

How was the engine oriented when you were flushing? Was it tilted more than 10 to 15 degrees from vertical? Carbs are sensitive to orientation... tilt too much and they starve for fuel (since the float keeps the needle valve closed).

[BarryB]

Hi Steve,
The impellor in the lower unit controls the amount of water that circulates. The speed of the impellor is controlled by engine speed since it is physically attached to the drive shaft. Yamaha motors also have a thermostat that controls water flow. Until you test the motor in the water, at idle for a length of time, your just guessing.

[Steve762us]

Originally Posted by Lucky

Not possible, unless you have a clog in your exhaust... but then the engine wouldn't run at all.

Roger that...I'm coming from Rotax engines, where you can indeed flood your cylinders, if water pressure > exhaust pressure. Good to know THAT is a possibility I can eliminate.

How was the engine oriented when you were flushing? Was it tilted more than 10 to 15 degrees from vertical? Carbs are sensitive to orientation... tilt too much and they starve for fuel (since the float keeps the needle valve closed).

The engine was in what I can only characterize as " typical operating posture"---not trimmed down all the way to the transom, but a few inches off it, not anywhere near the travel-lock setting.

I'll pop the cowling and eyeball what I can...maybe pull the plugs...once it cools off a bit.

Steve