I have an old Mercruiser 140 in my boat. The last few times I have taken it out and the boat runs great but after a day (or even an hour or so) of running the motor has a rough idle, bad enough that it often dies. When this is happening you can rev it back up and the motor runs normal. It’s just becoming an issue when trying to get it back on the trailer. After I got it on the trailer this afternoon I came back home and cranked it up to flush the motor out and the idle had returned to normal. Its about 20 minutes from the ramp tp my house. Any ideas?
Have you decarb’d lately?
“I am constantly amazed at the stupidity of the general public.”
~my dad
Equipment:
190cc Sea Pro w/130 Johnson
1- 15 year old
1 - 11 year old
1 - wife (The Warden)
ECFC
As in sprayed carb cleaner down the bores? Yes, but maybe I didn’t do too good of a job at it.
you need a carbon treatment chemical like carbonfree or quickleen and spray it down the carb and let teh motor sit about 20 minutes, then do it again.
afterwards, you have to change the oil.
it could also be an issue with the auto choke.
if you need help with it, contact “spareparts” on here. he is awesome with I/O
thanks for the compilment Chris,
sounds like the carb needs to be gone thru, if thats not it, check the distributor for shaft wear, it could be changing the point gap when its running, which effects timing, making it idle different. I don’t like to use a decarb on I/O motors unless i know it has a carbon problem
I took the carb off the motor Saturday and went to town on it with the carb cleaner. Like I said it always idles great unless its been going for an extended period of time but it did seem to idle a little better after I gave it a deep cleaning. Also, when revving it up, there is always a little “dead” spot around 1700rpm that you have to accelerate through slowly but I revved the snot out of it and the motor responded great. Taking it out tomorrow so I will let you know how she idles after I run her all day.
did you dissasemble the carb? To rebuildone properlly, it will need to be taken aprt, cleaned thorghly, then reasssembled using a rebuild kit, that includes gaskets, seals and a new accelerator pump diaphram