1992 Johnson 120 V4 idle issue.

whatley

Cadet
Joined
Jun 6, 2011
Messages
7
Having an issue, or perhaps not, and could really use some insight; greatly appreciated.

Cold start on land with "ear muffs" on over the intake the engine starts fine and runs around 1.2K RPM (give or take). After a short time she begins to creep, gradually, up to about 2K RPM. At this point she wants to back down to around 800 - 1K RPM but gets close to stalling and gradually raises back to 2K. She continues in this fashion.

Here is what I have performed:

Last fall:

1.) Winterized (fogged, checked/changed lower unit oil, stabilized fuel, stored full, etc., etc.)

2.) Replaced water pump over the winter

This spring:

1.) Took fuel sample. Fuel appeared free of water or contaminants.

2.) Replaced fuel filter/separator

3.) Took an oil sample. Found what appeared to be water in the bottom of the oil tank. I blame old gasket on top of oil tank. Installed complete and new oil tank assembly.

4.) Because oil tank was replaced I added 2-stroke oil into the fuel tank (pre mix). 5 quarts for a 62 gallon tank.

5.) Replaced thermostats. I hope I did this correctly, not sure how I could screw it up. Followed seloc and schematics.

6.) Fogged carbs again for good measure.


Some observations:

She is smokey, obviously from the pre mixed oil as well as the regular supply of oil.
Could this be the issue; too much oil? Buy why the high RPMs wouldnt she stall instead?

She is spitting water just fine, so the water pump install must be ok, but I noticed after running the engine for a short time then turning it off that the left cylinder bank
seemed quite a bit hotter than the right. Stuck or broken thermo?

This engine ran 100% without so much of a hiccup all last season and saw plenty of hours. Compression test read ~130 in each cylinder.

I have heard that without back pressure the engine can idle a bit higher. But why the up and down idle?

Appreciate any thoughts anyone may have.
 

whatley

Cadet
Joined
Jun 6, 2011
Messages
7
Re: 1992 Johnson 120 V4 idle issue.

Well...go figure. I threw the boat in the water and everything seemed fine. Ran the engine for a pretty good distance without hesitation or issues. So my note to any that stumble across this thread: The engine can run very differently when running on the muffs.
 
Top