1991 XR4 150 Hesitates on Acceleration

[27739]

1991 XR4 150 (s/n 0D015295). When I “punch it” from part throttle to full throttle, it hesitates for a little, then takes off and runs fine. I’ve just rebuilt the carbs with new gaskets, and everything looked very clean. Unfortunately, the accelerator pump rubber part was not included in the gasket kit and is only available in a rebuild kit that’s $85 per carb and full of stuff I don’t need (springs, needles, etc.) Sierra gasket sets do not include this part. When I manually actuate the butterflies, I still get a healthy shot of fuel from the accelerator pumps into the carb throats.

Any thoughts to help cure the hesitation?

 

[andy6374]

Re: 1991 XR4 150 Hesitates on Acceleration

Could try a lync and sync.

 

[LubeDude]

Re: 1991 XR4 150 Hesitates on Acceleration

When I manually actuate the butterflies, I still get a healthy shot of fuel from the accelerator pumps into the carb throats.

Am I missing something, When did they start putting accelerator pumps on 2 cycle outboards? I`m not the sharpest knife in the drawer but I have never heard of this.:^

 

[27739]

Re: 1991 XR4 150 Hesitates on Acceleration

So far, this is the only outboard that I've worked on that has accelerator pumps on the carbs. I had a Yamaha 90, and several "off-brand" smaller outboards and none of them had this.

I don't know which years/models/etc. that Mercury installed them on, but I can verify that they're on a 1991 Merc XR4 150. One accelerator pump per carb, installed on the port side, feeds a shot of fuel into each throat on acceleration. Line items 18 thru 25 on the diagram shown on mercurypartsexpress.com.

 

[j_martin]

Re: 1991 XR4 150 Hesitates on Acceleration

I've found the trigger getting a little gummy and sticky on old V6's. Check to see that the timing advances fully and smoothly when you operate the throttle.

hope it helps
John