99 Outback LS stumbling issue

[SkiBoy]

My Outback is still not running right. Carb has been rebuilt, fuel pump checked and pumping plenty of fuel, fuel water separator changed, new plugs, checked compression, new cap and rotor, timing is advancing, still running poorly.

The boat idles perfectly. Revs up to 4 grand with no issue. Transmission and prop and shaft all checked. I put it in gear and as soon as I add throttle it stumbles and vibrates. Advance timing, no change, retard timing no change. 2 mechanics have looked at it and listened in the water. One doesn't know, the other thinks it could still be in the carb. I am stumped and frustrated. Only 200 hours since the engine was rebuilt.

[Stazi]

Either the timing isn’t advancing properly under load or the main jet(s) on the carb are not right.


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[parrothd]

Either the timing isn’t advancing properly under load or the main jet(s) on the carb are not right.


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Did you check the accelerator pump? Can you slowly get over 4000rpm?

[SkiBoy]

The timing is advancing. It will rev up to 5000 plus, just not under load. Carb was rebuilt, it idles better and runs smoother until you put it in gear.

All parts on the carb were replaced.

[parrothd]

The timing is advancing. It will rev up to 5000 plus, just not under load. Carb was rebuilt, it idles better and runs smoother until you put it in gear.

All parts on the carb were replaced.
Pour some fuel in the carb while it's stumbling.

[SkiBoy]

Will do that tomorrow. I have the carb off checking it over. Thanks

[parrothd]

Is the choke opening after starting?

[Stazi]

Hmm. Accelerator pump usually has a couple of settings you can select, try using the next one up that has a higher leverage and pumps more. But first see if you can sloooowly get up to 5000rpm under load. If yes then try the accelerator pump adjustment. If that still doesn’t help then the main jests may have been redone incorrectly or are not clean.


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[jtucker]

The carb rebuild kit I ordered came with the wrong power valve. So I had to buy the right one separately. Do you know if the correct one was installed during your rebuild? The wrong one could be causing your problems.

[SkiBoy]

Yes, I did get the correct power valve after calling Holley. Ordered it separately from the rebuild kit. I can't get past 1500 rpm without shaking and vibrations. I poured gas in the primaries and secondaries (just a little) and it wanted to stall. I retarded the timing it got worse...advanced....no change. Don't know if the choke is opening, it has always run rough at the start then runs better after it gets to 120 degrees or so.

[SkiBoy]

Hmm. Accelerator pump usually has a couple of settings you can select, try using the next one up that has a higher leverage and pumps more. But first see if you can sloooowly get up to 5000rpm under load. If yes then try the accelerator pump adjustment. If that still doesn’t help then the main jests may have been redone incorrectly or are not clean.

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Will check the pump when I get some help. Tough doing these adjustments alone in the boat. Better to have someone looking at the carb while it is not performing properly. Thanks

[SkiBoy]

I di some adjustments and got the stumble out up to 3600 or so under load. Still is not running right and sounds a bit off. I will get a timing light and get my mechanic to tweak the carb. I ski at 36 or about 3800 on my tach so I want to get this smoothed out before I ski with it. Most likely the timing is off a bit. I may advance it and see if that helps, or just try and find the sweet spot.

I will report back after that. Thanks for all your help and suggestions, I learned a lot about my boat.

[SkiBoy]

Added some fuel treatment and advanced the timing a bit. It seems to come out of the hole better than before. I think the last carb rebuild used the wrong power valve. Runs right up to 4000 now. Still a little skip and stumble and a fuel drop off, but then it comes back. Running much better every time I take it out. Carb tweaks should put me back behind the boat in a few days. Thanks for all the help.

[zabooda]

I went through two electronic ignition modules separated by a decade. The second one cost me a carburetor rebuild which was probably needed anyway. Both times mine ran very unpredictable.

[SkiBoy]

Thanks......I have a mechanic coming to tune the carb this week. I added sea foam and some heat to the fuel and it is running smoother up to 4000 + rpm. Slight stumble on startup....and the idle is tough to set. May need a timing check and a few tweaks. I will post again. Thanks

[ranger098]

Thanks......I have a mechanic coming to tune the carb this week. I added sea foam and some heat to the fuel and it is running smoother up to 4000 + rpm. Slight stumble on startup....and the idle is tough to set. May need a timing check and a few tweaks. I will post again. Thanks

Any update here? i have a similar issue that remains a mystery to me, im about in the same place as you. looking at the carb.