Question?

[BarryB]

Okay, my boat is pushed by a 2006 (sold in 2008) Yamaha 70TRL 2 stroke motor.

The motor had developed a miss at idle. Not a steady miss like a missing cylinder, more like: idle...idle...idle...cough (repeat). I did the usual: changed spark plugs, no difference. Check all linkages according to manual, no difference. checked timing, on the money.

I let the boat sit until I had a moment a few weeks later. Tried to start the motor and it would not light up. Removed the intake cover and sprayed some carb cleaner in each carb., the motor ran for a moment then died.

So, a fuel problem. I noticed a red linkage. Read the notice on the intake cover. It states the red linkage is an "emergency fuel enrichment switch". I turned the linkage (was stuck at first) back and forth and this time, the motor fired up. Even more amazing, no more misfire.

Question is: What exactly does the red linkage do?

I looked in the exploded diagram of the carb. and I can't tell what the linkage turns or opens.

Does anyone know?

Thanks for the help.

 

[fridaysoff]

Barry,
Could it be a manual choke and it was stuck in the on position? Just a guess.

 

[BarryB]

You may be on to something...

The switch is located in the same area as the electric fuel enrichment device (choke). So I would assume it adds extra fuel. I want to find out exactly how it does it. Does it lift up the valve? Does it act as a bypass for fuel?

I figure if I know how it works, it might answer for the miss when at idle.

As always Friday, thanks for the help.

 

[Dave LeGear]

You "might" get a hint of it's operation by looking at the parts blow up which you should be able to find here

Yamaha OEM Parts ? Outboards, Outboard Motors

 

[BarryB]

Yep, seen it...

Thanks PS. I have the same "blow-up" in the Yamaha service manual. Since you found it on the computer, look at part number 29. It is listed as a "cover" but if you look just where the line points to (from the number 29), you will see a "V" shaped device; that is the "emergency fuel enrichment valve".

Number 33 is called the "starter" but is really a choke, sort of. I believe is opens when I push in the starter switch (while turning to start the motor) to add extra fuel for cold starts.

At this time, (As Friday stated) I assume something was partially stuck open which created the first problem, misfire at idle.

When it warms up here (lows in the 40's), I'll pull the boat out and fire her up again.

 

[Dave LeGear]

Could have been and if the ice ever melts off of it (as I set here freezing in a house never designed for such weather) some throttle body cleaner can work wonders on such parts and throttle body cleaner (unlike carb clearer) will not cut off any special coatings.

I would also check the plugs to see if you have one breaking down? I found these plugs here of late that look interesting...

Spark Plugs | Automotive Spark Plug | Motorcycle Spark Plugs | E3 Spark Plugs

 

[FishinFool]

My 50 two stroke manufactured in 2007 has a "v-shaped" handle that you turn to to "enrich" the fuel to the motor when it is cold. This works by adding fuel into the system and is not a real choke. The "normal" position on this is not well marked, and I have found out (the hard way) that if it is slightly off, it will leak fuel into the system and cause the engine to run rough...even cause it not to idle.

Hope this helps...

Tony

 

[BarryB]

Yep, that's the little bugger...

Hi FF,

I think you are correct. I never touched the switch before, but, perhaps from not being used, something stuck inside the carb.

Have not had a chance to run the motor since it's been cold out here. Perhaps this week.

I'll post an update when I test out the boat.

PuterS, I did replace the spark plugs and there was no difference with the misfire.

 

[BarryB]

So far, so good

Took the boat out and hooked up the muffs.

Motor started right up. No misfire.

Taking the boat for a weekend cruise to Boca Chita Key (1/22 to 1/24). That will be the real test and I'll report back.

 

[Thfireman]

Just wondering if you made it back safe or are you missing? Hope all went well and you have had no further problems.

 

[BarryB]

Sorry, forgot all about this post.

Yes, the boat ran fine. However, it still boggs down sometimes. For example, when power loading the boat the other day, when I gave a bit of throttle, it just bogged down and quit. I flicked the "emergency fuel enrichment valve" on and off and then the motor ran okay.

There is something up with that system. I started to run Chevron Techron in the fuel and will push a few tank fulls through to see if it fixes the problem, if not, I'll take apart the carbs and look for gunk.

 

[Thfireman]

OK, I have had other motors act like that before but not my current Yamaha. In the past as well with my Motorcycles I have put Sea Foam in my tank and ran a tank of fuel through it. Most of the time it cleaned up and ran real nice afterwards. Just a thought. Good luck in the future and if anything changes for better or worse let us know. Thanks, Roger