mercury 135 stumbles/stalls when put in gear

[jrnewman67]

1991 mercury 135 - motor starts, idles perfect until you put it in gear. at that point it either stumbles or stalls and shuts off. i have rebuilt the full pump, checked the thermal air valve, check fuel hose for cracks or leaks. i have also set the timing to factory settings. any ideas?

 

[hkeiner]

Re: mercury 135 stumbles/stalls when put in gear

i have also set the timing to factory settings.

Perhaps your idle speed RPM is too slow and shifting into gear kills the motor because of the added load.

You probably already know this if you did a link and sync according to the shop manual, but idle speed timing is typically specified as a range (e.g., 0 - 9 degrees ATDC) and the actual idle speed timing should be whatever it takes to get the motor to idle within the proper RPM range (as specified in the shop manual) with the motor in the water and in gear. If idle speed timing is set with the motor in neutral, then idle speed is probably set too slow.



This is just one suggestion. Others on the forum may have additional or better suggestions.

 

[jrnewman67]

Re: mercury 135 stumbles/stalls when put in gear

thanks for your reply.

it is idling 1100 rpm in neutral, in the water. as soon as i try to put it in gear it instantly shuts down.

i am considering hooking up a portable (temporary) fuel tank/supply or rebuilding the carbs.

does it run on all (3) carbs when idling?

Thanks for your input!

 

[hkeiner]

Re: mercury 135 stumbles/stalls when put in gear

I think it is spinning plenty fast enough. It is hard to imagine why it would die placing the motor in gear with that rpm unless your lower unit is the problem. I am sorry but I'll have to leave this to other more knowledgeable and experienced persons on this forum to help you out. Good luck.

 

[Scaaty]

Re: mercury 135 stumbles/stalls when put in gear

I'd suspect you tach might be a touch off...crank the idle up and try it..major "clunk" into gear, then the idle is too high, and its something else