Yamaha 250hp 2 Cycle - Bogging Down?

[ReelToy]

Check your pickup in tank ethanol is breaking loose a lot of old sludge in gas tanks. Screen in tank could be sucking up trash intermittently. Also gas hoses have been separating inside and collapsing another ethanol dilemma. Especially the gray hose. After that have carbs rebuilt by a competent mechanic.

[jeff6645]

I am back... work has kept me tied up.

Ok made some progress; after trying the "fuel can" idea was able to rule out a fuel delivery issue.

Pulled the carburetors, cleaned and set the pilot screws to 5/8 as the manual stated (they were set @ 1/4 to 1 turn). Cleaning the carburetors made a world of difference no more bogging down. But after idling back through the no wake zone developed a miss and lots of smoke and gas smell. Pulled the plugs, 3 of them were soaking wet. Changed them and adjusted the two pilot screws I could reach to a 1/4 turn from a soft seat. Ran much better. Got home and adjusted the other carburetor to a 1/4 turn and took her out again. Almost back to normal but still not 100%, pulled the plugs and they look pretty consistent in color and wettness... scared to tweak the plot screws to much.

Also checked the plug wires getting 7.2 - 8.4 ohms resistance on them....

Now running around 4800 RPM tops (41mph)... was around 5200 RPM (45 mph) before the bogging down issue started. But not complaining.

[bbh57]

I just worked thru a problem on my 98 carbed yamaha 200. It needed constant bumps on the choke to idle and it would bog down while running and again using the choke I could get it to preform for a short distance then id need to pump it again. I pulled the carbs cleaned them no help. ran a seperate tank nothing, I also took apart one of the fuel pumps it looked fine. finialy I decided to de-carb(I have not ever done this to this motor.) using sea foam. It did the trick. although the seafoam may have cleaned somthing I missed besides the carbon, Its running great now.

Here is the seafoam de-carb procedure I used.

Also Yamaha wanted 53.00 each for new bowl gaskets!

http://www.switchbait.com/forums/showthread.php?t=159

[jeff6645]

Thanks bbh57, I will give it a try.

I have read about using Seafoam to decarb but was never really sold on the idea. I read were they talk about it smoking while doing the decarb and thought it was just the Seafoam burring off... but after reading this procedure where it stops smoking after 2 or 3 times I am more convinced.

Thanks again for the link, I will let you know how it goes.

[bilgerat]

Ive read something about 02 sensors on a yamaha clogging up with carbon and causing surging, loss of power and excessive smoke, might check into that

[jeff6645]

Tried the Seafoam decarb mixture...

Mixed 3/4 gal gas, 1 can of Seafoam and 3oz of two cycle oil.

Removed the line going to the primer bulb and gave it a few pumps started the motor and let idle for 15 minutes. About 5 Min's in it started to smoke like it was on fire. Cut motor off after 15 Min's and let set for 15 Min's... discovered that in 15 Min's of idling the motor used almost the whole gallon of fuel... only about 6 oz left.

Restarted the motor after 15 mins and it smoked like crazy!!! Ran better, but still not back to normal.

By doing this test I may have discovered the problem. 1 gallon of fuel in 15 Min's while idling seems really high so I think it's a choke or fuel pump issue...

PS: on the way home today broke an axle, had to rig up a brace to get back to the boat ramp to launch the boat so I could take the trailer about 20 miles to get it welded So new axles will be required ASAP...

[Bushwacker]

My old carbed 115 V-4 burned 2 gal/hr at idle, and a V-6 would burn even more, so the fuel you used sounds about right!