acceleration problems

bdavis

New member
I've got a new 40hp Yamaha outboard 4 stroke on my boat. It ran perfect last fall when it was put away. It was fogged at the dealership where I bought it. All the old gas was drained from the tank in the fall.

Now, after four tanks of fresh gas this spring. The motor still idles rough and bogs when accelerating. What I mean by "bogs" is that it's almost as if it cuts down to one cylinder when I give it gas. If I back off on the throttle quickly then accelerate again, it picks up but still kinda spits and sputters and chugs for the first few hundred feet until it clears up.

Any idea what might be causing this? I'm thinking a stuck needle in one of the carbs. THis is the first time I've ever had an outboard engine fogged before storring it. Actually, I didn't even ask the dealer to do it but they did anyways since the boat was there in the fall for other warranty work. I've never had a problem with an outboard before in regards to winter storage. Could the fogging have gumed up one of the carbs?
 

Doc

Liquid Addiction
Staff member
I've fogged my boats yearly for 18+ years. Never a problem because of that.
Fog just coats the cylinders with a protective coating that will prevent rust and stuff while the motor sits for 7 months.
Like you said in my 'dry carb' thread. Our problems are similar, except that yours always starts. For mine most are guessing a fuel starvation problem. At least that is the cheapest fix (the cost of a fitting to replace the anti siphon valve).
What does the dealership say about your problem? I don't suppose you could need plugs already with it just a year old. but outboards are a different breed. I know when our jet ski was new it would foul plugs very regularly ... but after that first year the symptom went away. Anyway, it couldn't hurt to pull your plugs and check em out.
 

bdavis

New member
Already changed the plugs and that didn't fix the problem. Ran a can of seafoam carb cleaner through it and no change. Checked all the clamps on the fuel line and no difference. Any ideas???
 

Doc

Liquid Addiction
Staff member
Would it be hard for you to switch your fuel supply? That was a suggestion by more than one person for me, but I can't figure out a way to accomplish that with the way all my engine is closed in. Maybe it would be easier on your boat.
 

bdavis

New member
Still having problems with the motor. I fixed the idle problem myslef by simply turning the low idle screw three curly ones to slightly increase the rpms when idling. It still bogs when I first go to take off. It kinda spits and sputters when I accelerate for the first time. I let the motor idle for a few minutes to give it time to warm up then idle slowly away into deeper water before throttling up. After I run it for a few minutes, the motor runs fine. I tired it several times by slowing down and speeding up, coming to a complete stop, putting it in neutral then back into forward and nailing it on the accelerator and it runs fine. Well, most of the time anyway. The odd time I might feel a slight resistance from the engine.

So, it seems to only be doing it when its cold and being taken up to speed the first time then smooths out. Could this possibly be a choke problem?
 
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