does 115 Merc rebuild need new jets?

[h2oTherapy]

I noticed a comment in one of the earlier posts regarding rejetting when an engine is over bored (hopefully not overboard) as part of a rebuild.<br />I am rebuilding my '90 Mercury 115 (4 cyl). 2 pistons are getting replaced and they are .020" oversized (per machinists suggestion). Per manufacturer manual I am only replacing the bad pistons, and just replacing rings (and honing the cylinder) on the 2 good ones. I haven't finished the power head assembly yet, but have not planned on doing much carb work aside from general cleaning and lub. Is a re-jet something I should consider or should I wait and see how it runs and then decide.

 

[Red De Braal]

Re: does 115 Merc rebuild need new jets?

Hi : H2O You should keep the carbs sicronized (same) or you will have problems like two different motors in one block.

 

[ODDD1]

Re: does 115 Merc rebuild need new jets?

H2o..when I looked at your post, I assumed a inline 6...and would have said yes, bump up the mains .002"....the 4 cyl motors were more tolerant of a lean mixture, but if you scored two cyl from heat, a 2 thou bump in main would be a little insurance for the effort you are putting forward....

 

[h2oTherapy]

Re: does 115 Merc rebuild need new jets?

ODD1, yes, the cylinders were scored from heat, but I don't think it was because of an oil shortage (I assume that is what you meant to indicate the reason for adding more fuel, thus more oil, thus less over heat), After taking the water jacket cover off, I found enough sand inside too make me want to dig my toes in and take loooong sips off a cold one.<br />Or were you refering to the over heat for a different reason?<br />h2o

 

[ODDD1]

Re: does 115 Merc rebuild need new jets?

H20, if you have nailed down the cause of failure to an external reason [blocked cooling] i would not change what you have now....it worked before, it will work again.....