Poor idle/won't hold idle

[karlforester]

I have a 1998 mercury 175hp carb serial number 0g606952
Rus great at every thing but idle, at idle it will run ruff/stall in gear and in nutral, now if I bump it up just a bit it will be fine, makes it hard to dock and mauve when idling in gear or in nutral waiting to go to reverse,
Have had carbs cleaned and fuel pump rebult/tuned by merc dealer. I have put all mercury fuel lines and primer ball, new stator and trigger , still same problem all parts o.e need help figuing out problem and advice would help or if someone had same problem

 

[jjacobs007]

Check choke isn't sticking on,

 

[Dukedog]

do you know how to check/set idle timing?

 

[karlforester]

i dont think the choke is sticking but i will re check, i know when im idling and its about to die if i push the key in to choke it, it wll catch it and rrun normal for a short period of time not very long at all,

and yes i set the idle timing and the WOT timing after the trigger/stator replacement

 

[Dukedog]

did you set idle timin' "by tha book" or in tha water in gear under a load... sometimes tha book specs don't quite work out, 'specially with carbs.

a positive response to tha enrichner usually indicates a fuel delivery problem.. but you said tha fuel pump was rebuilt?

 

[flyingscott]

Have you done a compression test?

 

[karlforester]

I'm doing one ethir today or tomorrow depending on time, will post results when I do it

 

[karlforester]

Did it timing out of water and put it to what tag on motor said

 

[karlforester]

i was told to take all plugs out and ground wires, then using a starter jump tool crank motor and set the timing, idle and full throttle. is there a better way of doing it ?? also thanks for commenting in and helping

 

[karlforester]

sorry for the delay, so just did a compression tes, all cylinders were less than 5psi apart, average 2-4 so that can rule the compression out,

 

[racerone]

Post your actual compression numbers.

 

[karlforester]

3 pumps cylinders between 82 and 86psi ,
Continous 110 steady each cylinder, can find actual specs from mercry.. any idea what the spec is

 

[racerone]

I would pull one of the heads for a look see at the cylinder walls.

 

[karlforester]

Whats good compression for this motor? And is that very low

 

[Dukedog]

do you have access to another gauge ta do a comparison?... 110 so so, border line for me.. 115 (on "known" accurate gauge) or more will pass... that motor has compression relief slots.. merc is very vague on compression numbers..

idle timing/rpm.. set with boat in tha water, in gear (ok on tha trailer) to whatever makes you and motor happy.. don't worry 'bout what book says.

 

[karlforester]

I just redid the timing with motor running In big tank, won't have time to do it on trailer until next week, hopefully it runs a little better, and that was a brand new gauge from mac tools

 

[racerone]

I can not believe that folks will replace stators and triggers and then the $40 head gasket is a problem !

 

[karlforester]

The money is not a problem, it the time to do it, I'm going to get my bore scope and look at it that way for the moment, in a couple of weeks when I'm cought up on work I will take the time to rip it apart,

 

[karlforester]

so got a break from work today took boat out with some tools, checked cylinder walls with bore scope, did not see anything that jumped out. took timing light out and stared adjusting timing with boat in water brother at controls, i didn't do it by the book i did it until i got it to run the best... but timing off from what it says,
spec is "4 degrees after top dead" now its set idle in gear to about 4 degrees before top dead center. runs holds idle better and seems tp be smooth about 700rpm
question is will this hurt the motor?????
next i will pull head gasket next chance i get i ordered them already

 

[Dukedog]

idle timing is set ta whatever makes you and tha motor happy... don't worry 'bout what "book" says.