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Mercruiser 5.7 - Hesitation on rapid Throttle opening

Hi Guys,

Just a quick question. I've got a 1996 5.7 litre Mercruiser with Carb. I replaced the ignition leads, distributor cap and rotor last night and the boat is now running much smoother than it was.

However, when I was testing the engine (without putting it in drive) I noticed that if the engine was throttled up at a slow/medium rate it revs smoothly. However, if the throttle is gunned, it bogs down for a moment and then revs up.

The above is what happens when it is warm. If the engine is cold you have to be really gently with the throttle or else the engine acts as if it is about to stall unless you throttle back quickly.

The flame arrestor is clean and all the filters are new. I'm fairly sure that it was like this before I replaced the ignition bits last night - it's just that now that the engine is running smoother it is more noticeable.

None of this really matters in the way I use the boat normally. I always leave the engine warm up before leaving the dock and I'm not heavy handed with throttle normally. I'd just like to sort this problem out is case it has any knock on effects on the engine down the line.

Is there any chance you could let me know the most likely cause of this is? Is it normal?

Thanks in advance for any help, Paul.

paul.rockley
Sep 5
2006
Second that, I was having a lot of problems with my 4.3, it acted the same way. BUT, when you look down the throat it did pump gas. On my accelerator pump, there are three different settings - tried them all - no real help but one was better than the other two. I knew my carb had to be re-jetted anyway, so when I opened it, I replaced the accelerator pump at the same time - problem gone. gorf
Sep 5
If the timing is set correctly the next thing I would check is the accelerator pump on the carb. Looking down into the carb with the engine off you should see it squirt gas into the throats when someone briskly pushes the accelerator.

paul.rockley@gmail.com wrote:

jamesgangnc
Sep 5
   

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