OMC stumbles on acceleration

shawnb

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Jan 9, 2009
Messages
29
I have an 83' OMC Stringer. When I take off in the water it stumbles badly but doesn't stall. When I get on plane it runs like a champ.

The guy I bought it from said it has always just done that. I have a hard time believing it came off the showroom floor with that problem. Can ya point me in a direction?

Thank You.
 

Bondo

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Apr 17, 2002
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Re: OMC stumbles on acceleration

Can ya point me in a direction?

Nope,... Not without knowing What motor,+ What carb...
 

F14CRAZY

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Aug 12, 2008
Messages
945
Re: OMC stumbles on acceleration

I had a similar problem...would stumble when given throttle and would get up to maybe half speed, but if you left it there a while it would suddenly fix itself. Found that my point gap was too large.

Your situation could be from a number of things. I'd check the fuel filter, filter on the inlet on the carb, and the pickup in the tank too
 

shawnb

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Jan 9, 2009
Messages
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Re: OMC stumbles on acceleration

the engine is the 3.8L with a 2bbl. Rochester carb.
 

shawnb

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Jan 9, 2009
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Re: OMC stumbles on acceleration

I changed fuel canister filter and inline filter at beginning of the season, didn't correct the problem.

Thanks for the tips.
 

chiefalen

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May 18, 2008
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3,598
Re: OMC stumbles on acceleration

You look in the carb when someone else gives it throttle and see if the accelerator pump is working ?

Should sqrirt a stream of fuel.

The choke is open all the way ?

The plate opening all the way ?

If its running good at full throttle ain't the fuel pump or filters.

It's a carb problem.

At idle it runs good?

What the idle in the water in forward gear?

You hammering it, or giving throttle slowly and gradual?
 

shawnb

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Jan 9, 2009
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Re: OMC stumbles on acceleration

I'll have to check the carb. out when things thaw out. Unfortunately I have it outside (covered) but buried with snow! It sat for a couple seasons before I bought it so maybe I need a carb. rebuild, from what I understand things gum up after while. I use Sea Foam with my gas hoping that helps keep things clean.
 

chiefalen

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May 18, 2008
Messages
3,598
Re: OMC stumbles on acceleration

I did that exact carb.

Take it off get the rebuild kit.

Take it apart, soak all the parts in accertone over night.

Buy a large can of carb cleaner with the straw.

Take out the pieces and blow dry the carb with compressed air.

Get every hole clean with the can of carb spray, every little hole.

Blow dry, replace accelerator pump, you will get a new seat and needle valve, install, and away you go.

Now be careful when you screw in the adjustment needles.

You have to screw them in than out follow the book, but be gentle do not bend the tips, when you screw them in, understand ?
 

Howard Sterndrive

Rear Admiral
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Nov 5, 2008
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4,603
Re: OMC stumbles on acceleration

look where the choke heat tube enters the intake manifold. They like to rust and develop a big vacuum leak there.
 

chiefalen

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May 18, 2008
Messages
3,598
Re: OMC stumbles on acceleration

Got a vacuum leak easy way to tell.

When running spray wd40 at the base of the carb and at the vacuum tube, if it runs better then you know theres a leak.

However if no leak then, rebuild carb, clean all the filters, one in the fitting at the carb, one in the fuel filter.

Run it, still not fixed than clean the filters again and run it off a external tank.

If fixed then the fuel pickup tube, ant-siphon valve might need cleaning.
 

chiefalen

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May 18, 2008
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Re: OMC stumbles on acceleration

The last post i am assuming the points are correct, the plugs are good and the wires are good.
 

shawnb

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Jan 9, 2009
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Re: OMC stumbles on acceleration

Yes, we tuned it up. Set the points, adjusted timing, plugs, wires.
 

chiefalen

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May 18, 2008
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3,598
Re: OMC stumbles on acceleration

Good Shawn look to the carb dirty. Had this same problem, 2 friends, 2 different boats this last summer.
 

mthieme

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Oct 6, 2007
Messages
3,270
Re: OMC stumbles on acceleration

Sounds much like the accelerator pump in the carb. You describe the textbook symptom of one which is failing/failed.
I have a 2 bbl Rochester on my 4.3 OMC. I get about 4 years average out of freshening up the carb. In fact I have a spare now ready to be swapped in spring.
Look down the carb and push the throttle to full quickly. You should see a squirt go down each side. If it doesn't, it's the accelerator pump; rebuild the carb.
 

shawnb

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Jan 9, 2009
Messages
29
Re: OMC stumbles on acceleration

Thank you for all the advice. Unfortunately I'll have to wait to remedy the problem until all this snow goes away. I surely will be using all the pointers!
 

mthieme

Captain
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Oct 6, 2007
Messages
3,270
Re: OMC stumbles on acceleration

Don't let a little snow stop you! We've got brethren up in Canada out there this weekend working on their boats!
Four bolts, a coupla cables then you can come back in and spread it out all over kitchen table!
:)
:)
:)
 
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