89 Johnson 70 hp idle question

[ASwan73]

I have a 1989 Johnson J70TLCEM 70 hp that idles at around 1000-1100 on muffs but put it in the water and it drops to 750-800. How do I get this so it idles at 1000-1200 rpms in the water? It will stall out of the rpms get too low. Replaced all filters and lines yesterday and check spark air gap is good and carbs are good. Do I adjust the idle screw while on the water or can I do it on muffs and take it up to about 1400 on muffs and it go down to the desired area while in the water since the water adds back pressure to the exhaust system.

 

[boobie]

Do it in the water.

 

[ASwan73]

Ok thanks. Should I adjust the screws or the adjust for all three plates that run off the lever?

 

[WernerF]

Do not adjust the three plates. The three carb plates must be absolutely closed at idle. It's the spark timing what determines idle rpm.
The throttle cable's travel is limited with two screws at the big lever on starboard side. The lower screw sets idle rpm.

 

[ASwan73]

Ok thanks. I'm gonna go through my service manual and do a link and sync on the whole thing so I can rule that out.

 

[Sirrobin53]

Ok thanks. I'm gonna go through my service manual and do a link and sync on the whole thing so I can rule that out.

Link and sync is a good place to start. Controls wear a little at a time causing all kinds of problems.

 

[ASwan73]

Did the link and sync and seemed to help a little but still stalls out and quits when I shut it down after a run so not sure what is going on with it. Will read through service manual some more to try and figure out.

 

[racerone]

Working on a like (1990 ) motor now.----stalled when put into gear.---Did compression test and determined the center piston was scored even at 110 psi on my gauge.----Bored and honed the center cylinder out myself and waiting for parts to re-assemble it.