Yamaha Outboard - No Power

[countrybimm]

Originally Posted by JUST-IN-TIME

RUN IT OFF AN NEW GAS TANK WITH NEW FUEL LINES

it can be the carb not rebuilt right

i would also do a compression check and read the spark plugs and check for spark

new carb he said, plus if its running then the plug is making spark..
my guess would be sensor

[markpj23]

I have tried the new gas tank & fuel lines, no luck. The only fuel line not yet replaced is the one inside the cowling, and I'm checking that one next.

I'll check out the oil sensor thing and the accelerator pump actuator. Carb is brand new and absolutely clean inside.

Thanks for all the suggestions!

[markpj23]

I found that the accelerator pump linkage was mis-adjusted. Fixed that but still not much power although it seems to try harder to run up to speed now. Oil sensor looks brand new, and because the engine does not just retard to idle I don't suspect this as the problem.

So I pulled it off the dink and will try another shop..... sigh.

[markpj23]

Yesterday I went to the shop and heard the motor run in their test tank with my prop on it. It seemed to run fine and make good power. They did nothing to it except adjust the idle speed, tell me to adjust the tilt / trim to find the best angle and bill me $53 for their 1/2 hour....

So I wrestled the beast back on the dinghy and tried again. I first verified that there was no water in the hull void space. All looks good.

The motor runs fine at low RPMs and up to about 3,000 estimated. Then it starts to falter as if it's starving for fuel - which I can't believe it is. New fuel lines, multiple tanks, clear in-line filter (also new) that shows no air in the line and yes the tank vent is open.

The mechanic said that if I was still having trouble he would take a look with the motor on the dinghy. I'm sure that will be pricey and I'm losing confidence in these outboard mechanics.......

I know this motor can get me up on plane - it starts to do that and then just loses power. $500 and counting..... good grief!

[Chief Engineer]

See if you can get him there "after hours" wink wink.

[JUST-IN-TIME]

they had problems with fuel pumps

also a new carb can still be bad

they run gas in them before shipping them out

i have seen a couple with varnish in them!!!

[Fiveslide]

Your problem is the cylinder sleeve. I guarantee it. A friend of mine had the exact same thing happen on a yamaha outboard, albeit, a much bigger one. The sleeve will spin in the engine case and cut off intake and exhaust flow. That's why it runs fine at idle and low rpms. Everything will test fine, but if you disassemble this motor the sleeve will not be in its proper position.

A fix so it doesn't happen again? Drill a small hole where the sleeve contacts the engine case and put a small pin in it.

Yamaha never once thought of this, and to my knowledge has never admitted it happens. It took some old, half blind man that works on boats in his back yard to tell him the problem before he ever even saw the engine. The old fellow knew his stuff, he also refused to fix it because my friend questioned how he could know the problem without even looking at the engine. He was stubborn man apparently.


Edit: Sorry, went back and read the original post. This wouldn't be the problem with a 4-stroke engine, this is a 2-stroke problem/solution.

[markpj23]

OK so the same shop that ran this in the test tank and pronounced it good sent a different mechanic down to the waterfront today. I waved as he took my dink out and saw that it did exactly what I had been telling them.

But this guy was smart enough to figure it out.... it seems that the previous owner had reassembled the carb to the manifold incorrectly, and everyone since had been repeating the same mistake.

Picture this: we had the intake manifold, gasket, carb, spacer plate and air intake tube - in that sequence. The mechanic today realized that the choke was partially engaged because the assembly was wrong. It should have been: intake manifold, gasket, SPACER PLATE, carb, gasket and intake tube.

The PO had put the spacer plate on the wrong side of the carb, and it was interfering with the choke butterfly.

This thing screams! No issues getting up on plane at all. Finally!

Now I need to go beat on them for wasting my first visit and not finding it before....

[JUST-IN-TIME]

i have seen that 1 time before!

[Jmolan]

Right on! The answer is always simple.....once you find the answer

[Intentional Drifter]

I think they own you some money. Regardless of what the PO did, they should have corrected it the first time. They are the "pros" after all.

ID

[Therapy]

Originally Posted by markpj23

OK so the same shop that ran this in the test tank and pronounced it good sent a different mechanic down to the waterfront today. I waved as he took my dink out and saw that it did exactly what I had been telling them.

But this guy was smart enough to figure it out.... it seems that the previous owner had reassembled the carb to the manifold incorrectly, and everyone since had been repeating the same mistake.

Picture this: we had the intake manifold, gasket, carb, spacer plate and air intake tube - in that sequence. The mechanic today realized that the choke was partially engaged because the assembly was wrong. It should have been: intake manifold, gasket, SPACER PLATE, carb, gasket and intake tube.

The PO had put the spacer plate on the wrong side of the carb, and it was interfering with the choke butterfly.

This thing screams! No issues getting up on plane at all. Finally!

Now I need to go beat on them for wasting my first visit and not finding it before....

Yahoo!!


Now.

I thought you said you replaced (or had "them" replace) the carb.

Funny how that little exploded picture don't work sometimes.

Zoom Zoom.

[markpj23]

Originally Posted by Therapy

....I thought you said you replaced (or had "them" replace) the carb....

Yes I first removed the original carb to clean it, then the "pros" installed a new carb. Trouble is, everyone was reassembling things the way it came apart.... which was wrong. And the air intake tube makes it impossible to see the choke butterfly ...

Ya just can't make this stuff up...

[Captain Bill]

Mark, I've taken off a few Yamaha Carbs (both my own and friends) and I clearly know which side of the carb the spacer goes on. With all the problems with carbs these days from the ethanol fuel, I can't believe that any real "Pro's" would not have spotted the problem right away. I suspect that you were the victim of the "Pro's" having the shop lacky (probably paid minimum wage) do the menial work of removing and installing the carb while the pro's did more valuable work. When this guy discovered this it was probably the first time a "Pro" had seen it apart. My guess is however that you got to pay at the Pro rate, not the lacky rate. I think these guys owe you some money back. Good luck with that.

[Therapy]

Originally Posted by markpj23

Yes I first removed the original carb to clean it, then the "pros" installed a new carb. Trouble is, everyone was reassembling things the way it came apart.... which was wrong. And the air intake tube makes it impossible to see the choke butterfly ...

Ya just can't make this stuff up...

Got it.
Amazing.
Good it works now.
Hope you didn't spend too much though.
But then a screaming dingy when you need one - priceless huh?