What is correct idle oriffice jet size-1988 johnson 48HP

[fisherman67]

I have had a nightmare of a time trying to get this motor to idle correctly without having to constantly push in on the choke. I have taken the carbs apart three times to make sure all small passages are clear, the last I even stuck a small piece of wire thru the passages to make sure there are no restrictions, but I did notice the idle orffice jet had 33 stamped on it and when I looked up what size oriffice should be in this motor it says it should have 36 jet. Could this small difference in sizes be causing the motor not to idle right?

 

[wilde1j]

Re: What is correct idle oriffice jet size-1988 johnson 48HP

You looked the jet number up in an OEM shop manual? If so, the book is right. BTW, the PL online calls for #36 idle jet. See BRP Evinrude website. How long have you owned the motor? Did it possibly spend time at high altitude before you got it? It may have been jetted for higher altitude. The jet size controls idle mixture.

 

[HighTrim]

Re: What is correct idle oriffice jet size-1988 johnson 48HP

Im not sure if the jet size is your issue or not, but I do know that you should physically remove the jet, using a home made special tool (see carb rebuild thread in Top Secret File) for cleaning. Youd be amazed at how many times people think the jets are clean, yet they are not. I like to completely tear the carb down, removing all jets, soaking overnight, blasting out with carb cleaner, washing with warm water, then drying/blasting with compressed air.

 

[boobie]

Re: What is correct idle oriffice jet size-1988 johnson 48HP

What's the compression like? When's the last time it was decarbed?

 

[Joe Reeves]

Re: What is correct idle oriffice jet size-1988 johnson 48HP

1988 48hp Johnson.

Idle air bleed jet = #36

High speed fuel jet = 50D

Dropping the idle air bleed jet down to #33 would result in a slightly richer fuel/oil mixture at the lower rpm range.