Mercruiser acceleration issues

Perkzk

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Jul 8, 2019
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Ive searched a lot but cant find a thread with my exact symptoms. I suspect carb/fuel but i would appreciate any other input. 2001 tahoe 220 deck boat. 5.0 mercruiser 2 bbl carb. Alpha 1 gen 2 outdrive (i believe). My main/most consistant issue goes like this...Engine generally starts pretty easy with a pump or 2 of the throttle. I believe the choke is electric and was unhooked by previous owner. Maybe a slightly rough idle during warmup but seems to smooth out. Warms up and idles out to the no wake buoy. Most times if you ease into the throttle the boat will get almost to the tipping point to get on pad and it starts to cut out. I can pull back just a bit for a split second and start back in throttle and it will pretty much pick up slowly and run on out...for the most part not giving it any more throttle. This usually around 1800-2200 rpm id say. I can not just slam the throttle ever. It will just fall on its face and eventualy die if you dont let out of it.

Whats been looked at...the fuel water separator is new, then tested, new filter dumped into jar to inspect, no issue, pulled filter at fuel line into carb and cleaned what little stuff i could see. Accelerator pump confirmed is squirting (first one ive ever looked at so i cant say its working like it should but it does squirt 2 streams). Tried all 3 settings on the linkage. One seemed a little better so i left it. It was originaly in the center. Boat has been ran with gas cap off to check vent issue.

Other things it does...
1. when loading on the trailer you have to baby it just the same as take off but seems a little more magnified.
2. It has “ran the bowl empty” running down the lake a time or 2 out of many long runs.
3. At one point it seemed to surge a bit at WOT but that has gotten better over a few trips almost to the point id say it has went away
4. Last season i had a time or 2 that i got a hard miss or backfire as i was running on pad down the lake. Not a normal thing and have not seen that this season.

Thanks for reading and any input.
 

alldodge

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Mar 8, 2009
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40,582
I'm seeing the need for a carb rebuild
Does it have a regular 2bbl carb or a TKS?

This is a TKS, note the larger connector
s-l640.jpg
 

Perkzk

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Nevermind the red circle this is just the pic that i had onhand
 

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alldodge

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OK, its a regular 2bbl
I would pull it apart and rebuild. Pay close attention to cleaning the channels in the carb. Look for some very small wire to try and clean them out the internal channels.
 

wellcraft-classic210

Master Chief Petty Officer
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Sep 22, 2010
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839
Agree on carb cleaning. The fuel must pass through some relatively small holes ( about 1/8 in dia ) and if thier is any blockage that will reduce max flow.

If you see any debris in the float bowl you will know your on the right path for trouble shooting. Replace the small fuel filter at the carb inlet as well.
 
Joined
Jun 9, 2019
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Mine did something similar to yours at low rpm. I am terrified of taking apart carbs so I looked at the timing and sure enough it was off 3deg. I set it correctly and the trouble went away. I have the TKS carb and 3.0L engine. It is at least something you can look at without taking anything apart. Good luck.
 

JASinIL2006

Vice Admiral
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Feb 10, 2012
Messages
5,525
My 350 Mag did this. A carb cleaning helped, but adjusting the timing is what cured it.
 
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