View Full Version : Choppy 9.9?

05-28-2004, 01:13 AM
Time for me to pick some brains ;).

I've got a Yamaha 9.9 that's been running rough lately. Some of you probably remember reading that it almost ended up as Lake Oroville bottom contour :-/. Ever since that bath in the lake, it's been choppy at idle and cuts out on me at full throttle every now and then. The list of things I've done so far is as follows;

-fuel system flush
-oil system flush
-new fuel filter
-new lower unit oil
-approx. 6gl of fresh fuel through the motor w/ Berryman's fuel additive

I'm thinking of getting a carb. rebuild kit from Yamaha but thought I'd see if anyone had any other "quick fix" ideas first.

Thanks for any ideas,


05-28-2004, 12:05 PM
Hi Erreck, sometimes decarbing can solve the problem. Its inexpensive and should do the job. There's a thread on the topic in this board. good luck!!

LTF 14 hrs columia!!!

05-29-2004, 06:09 AM
I had given thought to decarbing after reading that thread. But, I've always thought of that as being somthing that is for 2 strokes since the build-up of carbon and residue is a major problem there and not as much in 4 strokes, if at all.

I'll give the decarb. a try, but that's what I was essentally doing when I ran the Berrymans through the system. :-/

Anyone else have any thoughts?


05-29-2004, 11:04 AM
If you want of "decarb" a 4-stroke, a shot of Techron concentrate in the fuel might be a better choice that SeaFoam. 4-strokes tend to accumulate deposits on top of the valves and probably in the upper ring lands from burning stale fuel or from running too rich at high altitude. These deposits are more complex than the carbon that builds up in a 2-stroke.

From your symptoms, I don't think your problems are related to engine deposits. If the engine suddenly dies when running at high speed, I would suspect a bad electrical component or a sticking carburetor float. You should check the output of the coils (or computer, I'm not familiar with the 9.9 Yamaha). Rebuilding the carb after a dunking is always a good idea.

05-29-2004, 11:16 AM
Thanks Doc,

That's the direction I was leaning. I "know" that the problem is carb. related. The problem is figuring out if it's vaccuum, choke, electrical, or internal carb. issues.

Screw it! I think I may just take it to a pro if the rebuilt carb. doesn't work. :-/


12-28-2005, 10:10 AM
test pic

12-28-2005, 10:12 AM
test pic

12-28-2005, 10:18 AM

12-28-2005, 10:19 AM
test pic getting closer1

12-28-2005, 09:31 PM
I'm for the carb rebuild. You probably won't need the kit if your gaskets come off clean. Just dissamble and clean with carb cleaner(the carb that is not the gaskets). Just make sure you tighten the mixture adjusters and count the turns in quarter turn increments so you know where the mixture should be (roughly). Then adjust when runnng if needed.
hope this helps