Yamaha 70 2 stroke stalling

[scotchguy]

Just bought my '99 montauk w '00/70 2 stroke and had it out for the second time today. I stopped briefly (10 minutes with motor off after idling for about one minute) after running about an hour with zero problems. Upon restart, motor would not go above 1200 rpm and would die if I tried to increase rpm any higher. No alarm sounded. After 5 minutes adrift, I started motor again and was able to get back to the ramp at about 2300 rpm with motor trimmed all the way down and running rough. Rpms would fluctuate -500 +200 on the way as well. I plan on checking the usual things, plugs, fuel line, fuel filter, but I can't figure out why this problem would show up after an hour of flawless performance.

 

[scotchguy]

Re: Yamaha 70 2 stroke stalling

Pulled the spark plugs today. Why does one always fall to the bottom of the cowling just out of reach? The ones from the bottom and middle cylinders were wet with oil while the top was dry. I don't know if this is normal or not. Since I was there I also checked compression. All three were between 110 and 120. I did find a broken gasket on the fuel tank lid so my next step will be to buy a small aux. gas tank and see if fuel was the problem. I'm going to wait until the shop manual I ordered gets here before I go any further.

 

[butlp]

Re: Yamaha 70 2 stroke stalling

scotchguy,<br />You are proceeding correctly! Wait until the manual arrives and follow the procedure to set the timing and carb set-up. New plugs, clean the fuel filter and at the same time replace the water pump impeller.<br />Make sure the connectors on the fuel line from the tank to the motor are not leaking or sucking in air. If they need replacing it's cheaper to buy a complete fuel line with priming bulb from Yamaha.<br />Good luck!<br /><br />Is "Town of the Cow" Calgary?

 

[scotchguy]

Re: Yamaha 70 2 stroke stalling

Thanks for your response. Town of the Cow is Fort Worth TX.

 

[rodbolt]

Re: Yamaha 70 2 stroke stalling

whoohoooo cowtown spent many a good beer ther baby. I hear lake benbrook is a mud hole now though. anyway. also carefully flush your carbs. unless the linkage broke the timing cant change. it sounds just like some trash in the fuel bowls. drain and flush the. its the small brass 10mm hex plugs with a screwdriver slot on the stbd side bottom of each fuel bowl<br /> good luck and keep posting<br /> PS dont get caught weeing in public at the stockyards

 

[Vardar]

Re: Yamaha 70 2 stroke stalling

Hello guys, i have similar problem.

I ran my carolina skiff first I bought it a month ago, several times i was fine. And it started staling or just engine speed going down, gradually like few seconds. However this always worked. I stop, stop the engine, lift the engine put it down, and start again and it goes full force till we hit some serious choppy water. I changed the fuel filter element, and water/fuel seperator filter, still the same.... I disassambped the fuel filter yesterday didnt see dirt, still same problem?


Should I sacrifice the gas in gas tank and take it out, and clean it? It is driving me crazy, or maybe clean fuel line, does anyone know how to do it?(screwed up my Fathers Day (( )

Someone told me to manually pump the fuel line when stalling occurs but didnt help. FUel pump assembly is only 35 bucks but will it fix the problem?

I mentioned this problem in carolina skiff mechanical forum, someone said fuel pump is going bad... Just wanna make sure.. I am one of those DIY guys to save money....

Thank you very much in advance
Buddy

Setup

2001 17ft CS, 2001 70hp 2 stroke Yamaha

 

[waffles1]

Re: Yamaha 70 2 stroke stalling

Scotchguy, this is all excellent advice and your plugs should be tan and dry not wet and oily.

 

[onejaboney]

Re: Yamaha 70 2 stroke stalling

Hey there,
I live up in Colorado and just bought a BW 15 Sport with a 1985 Yamaha 70 ELTK on it .
Do you happen to know what settings the idle mixture screws are supposed to be set at?
What pitch prop are you using?

Cheers

 

[bugster61]

Re: Yamaha 70 2 stroke stalling

Hey, just a thought, I have had this problem....It really sounds like over heating. When rpms are higher flow might be ok, but when u stop it, the head does not get any cooling.......I had this exact problem... I replaced my water pump impeller, got a yamaha water pump kit, about 50 bucks...did the trick.....purrs like a kitten......

Hope this helps,

Doug

 

[Home Cookin']

Re: Yamaha 70 2 stroke stalling

My Yam 50 was acting stupid 2 weeks ago, too; rough idle on start; bogging out on accelerating; you had to feather the throttle to get up sometimes. I just talked to another owner who ws having worse problems, told him to replace the water seperator (that I had bought and left in the boat but couldn't swap out b/c my filter wrench was in another boat that died). He did, and it runs like a champ.
We run out of 6 gallon tanks, treat the fuel, seperator, never sits more than 30 days, usually kept in the shade.
Another wierd thing it would sometimes do, is not start unless trimmed all the way down. But I know for a fact there is no trim/kill switch. I suppose when it's perfectly level the water in the various places isn't being picked up. You rmentioning problems after bouncing made me think of that--you may be agitatnig bad gas, from the tank to the bowls, triggering a borderline probelm.
(Also when bumps cause problems, tighten your battery cables. Vardar you sound like a possible short/loose connection there. That's how electrical problems can mimic fuel problems).

 

[ttownguy]

Re: Yamaha 70 2 stroke stalling

Stale gas or water in the gas can cause problems. Try disconnecting the inlet hose at the fuel filter that's mounted to the engine. Port it to a clear bottle and pump the fuel bulb. If there's water present you'll see it.

Another sign of water is "beaded" liquid on the fire end of your spark plugs...you have to look close to see it.

I had to dump all of the fuel in the tank I could, got everything out of my fuel lines, then I filled it up and put in Iso-Heet (for two-stroke engines) and ran out the remaining water. Runs like a champ again.

 

[Vardar]

Re: Yamaha 70 2 stroke stalling

What do you suggest?
Reconnect batteries?

Thanks

Vardar you sound like a possible short/loose connection there. That's how electrical problems can mimic fuel problems).

 

[Home Cookin']

Re: Yamaha 70 2 stroke stalling

yes disconnect clean reconnect tighten with pliers. check all connections.