2-stroke bogging

[tommmmmg]

I have a 2004 150 yamaha 2-stroke that starts and runs fine but will bog if you try to push the throttle over ~3200rpm. Let me put down a quick timeline
1 boat purchase at auction runs ok but bogs at 3krpm
2 mechanic tune up same thing
3 mechanic rebuild carbs
4 I receive boat install carbs same thing
5 I put extermal tank and new fuel line to engine same thing, bogs
6 bring to 5 star yamaha mechanic says carbs ng $1500+ for new ones
7 bought "rebuilt" carbs installed same thing
8 bring to another yamaha mechanic checks everything and installs new fuel pumps EXACT SAME THING
This happens only under load hence a mechanic can't fix it??
One hint is that if I'm running under load go back to the engine and by hand increase the throttle while closing the chock she'll run right up to 5k rpm no problem. Told the mechanic that and I get another let me see what I can do?
Anybody got any ideas? Seems like it is starving for fuel? Maybe new fuel lines from the internal fuel filter to the carbs themselves?? Thanks in advance for any suggestions

[ThanksandGigem]

Here is my thread had a similar issue in January. I'm about 90% sure it was the pumps. Mine were only 30 bucks brand new and there was 2 easy fix that takes about 10 minutes.

http://www.yamahaoutboardparts.com/f...t-th26284.html

[scofflaw]

I think it's reasonable to assume that if fiddling with the linkage and choke makes it run properly, you got yourself a linkage and or choke issue.

[RayBersch]

I think it's reasonable to assume that if fiddling with the linkage and choke makes it run properly, you got yourself a linkage and or choke issue.

Whoa, here my friend. His fiddling increased the fuel supply and decreased the air supply, the linkages and choke were likely passengers along for the ride. A ride, by the way, that seems to be powered by incompetent mechanics all along the way. There will be competent help offered from this site very soon.

Ray

[tommmmmg]

2-stroke bogging

Fuel pumps rebuilt by mechanic. Primer ball stays hard and squeezing has no affect. When I say fiddling with the linkage I mean I'm working the throttle by myself at the engine while running under load. (on a hose no problem revving right up) The key is by slowing closing the choke I can open the carburetors more without it bogging. I can hold the choke partly closed and the engine will run at 5000 rpm's no problem. So my reasoning is I'm running lean? It could be the carburetors themselves but after 3 mechanics addressing them it seems unlikely. The only thing I can think of is replacing all the fuel lines under the cowling. I'd hate bringing to another mechanic and have another $300 bill with the exact same results. Thanks for any ideas

[ThanksandGigem]

Whoa, here my friend. His fiddling increased the fuel supply and decreased the air supply, the linkages and choke were likely passengers along for the ride. A ride, by the way, that seems to be powered by incompetent mechanics all along the way. There will be competent help offered from this site very soon.

Ray

I completely agree sounds like my issue where it is just simply a fuel restriction. All fiddling with the choke does is confirm it is being starved of fuel.

[rodbolt17]

DUDE

whoa up a bit and think about it.
also find a real mokanic.

all the choke does is force the fuel system rich by bypassing all the idle,intermediate and main circuits.

by closing the choke slightly your forcing it rich by BYPASSING all the carb circuits.

means there IS fuel available in the fuel bowl you just cannot get it from the bowl to the delivery nozzle.

do the carbs correctly.

[tommmmmg]

bogging

So your thought is that it is it the carbs? Not a restriction to (before) the carbs. There appears to be no high speed jets to adjust. Is the float a consideration? These carbs are supposedly good?

[ausnoelm]

Correct, there is no high speed jet to adjust, that's why it must be clean! Any "mechanic" that wants to replace carbs needs to be flogged with a length of fuel line!

[scofflaw]

Odd unexplainable part is there have been 2 sets of carbs installed with same result.

[tommmmmg]

2 stroke bogging

I agree everything that has been done including 2 different sets of carbs resulting in the EXACT same result. Bogging at ~ 3200rpm. I ordered all new fuel lines under the cowling and will replace them as soon as they come in. See what happens!?

[TownsendsFJR1300]

If your half-ways mechanically inclined and can get the carbs off, the rest isn't hard.

Simply pull the float bowls and find the main and idle jets. Use either your shop manual or provide an exact MODEL # and year (so we can refer to a carb parts fisch).


Plus 1 on flogging the mechanic to replace the carbs, guess its easier than cleaning...


Once you get to the jets, PULL them OUT. If you can't see light thru them, IT DON'T COUNT..

You have spares to practice on as well. (I'd clean the originals and use those myself)

[scofflaw]

What are the odds of 2 sets of carbs producing the same exact problem ?

[tommmmmg]

I'll give it a shot. I've rebuilt carburetors before but it's been awhile. I thought it would be easy just bringing it to a mechanic. Buy a carb rebuild kit? Thanks for the help

[TownsendsFJR1300]

I'll give it a shot. I've rebuilt carburetors before but it's been awhile. I thought it would be easy just bringing it to a mechanic. Buy a carb rebuild kit? Thanks for the help

I can't remember the last time I bought a kit (un-less you find something wrong).. I'd just get to the jets and pull em..

With the RPMs you are getting, one or two jets are clogged, the other cylinders are hitting...



For scofflaw; varnished up jets, clogged, ALL the time on Ethonol fuel un-treated.

Easily, 95% of the engines I have to get running are crapped up fuel systems, varnished and clogged.. Just did one on a Honda 2000 watt generator carb. Main jet clogged up, (aluminum float bowl BROWN big time with varnish), cleaned, first pull-started and ran great.

That customers second generator carb, it ran for a little bit, then started spitting fuel out and died, Found the FLOAT FULL of fuel...