1992 Johnson Evinrude 120 hp

[ezeke]

Re: 1992 Johnson Evinrude 120 hp

Did you replace the thermostats yet?<br /><br />Have you tested the recirculation check valves?<br /><br />Someone asked before if you are pre-mixing fuel??<br /><br />What is RPM at planing?<br /> <br />Top RPM? <br /><br />How long since the last De-carb?<br /><br />What size and pitch propeller?<br /><br />Can you post a picture showing how the motor is set in relationship to the transom?

 

[littlemac]

Re: 1992 Johnson Evinrude 120 hp

I have not replaced the thermostats yet. The machanic that i am using said he did not think it was the thermostat. I can't get the RPM because my tach. is not working. I am pre'mixing the fuel. What size propeller does it carry? I can post a picture of how the motor is set on the transom tomorrow. I do have a jack plate. Where are the recirculation check valves? I have given up on my machanic. <br />Thanks very much, <br />littlemac

 

[ob]

Re: 1992 Johnson Evinrude 120 hp

I'm still interested in knowing whether the last plugs that fouled were the QL77JC4 or the L78YC.

 

[marysboats]

Re: 1992 Johnson Evinrude 120 hp

If the engine is in sound condition, you could do as I discribed. A voltage running test would tell what component in the ignition system is breaking down if that is the problem. Doing cranking test's on the trailer may very well not show the problem. This test would show what component is failing, sensor, charge coil, power pak. You could then narrow it down to the ignition coils, or a faulty connection. If the ignition check's out, do a pressure, vacuam test on the fuel system. This is going to take the proper equipment, but without, you are groping in the dark. Tool's can get exspensive, but so can needless part's.

 

[littlemac]

Re: 1992 Johnson Evinrude 120 hp

Its fouled out both types of plugs I/ve bought nine sets of plugs since Feb.

 

[marysboats]

Re: 1992 Johnson Evinrude 120 hp

I think we can rule out spark plugs.

 

[littlemac]

Re: 1992 Johnson Evinrude 120 hp

Originally posted by ezeke:<br /> Did you replace the thermostats yet?<br /><br />Have you tested the recirculation check valves?<br /><br />Someone asked before if you are pre-mixing fuel??<br /><br />What is RPM at planing?<br /> <br />Top RPM? <br /><br />How long since the last De-carb?<br /><br />What size and pitch propeller?<br /><br />Can you post a picture showing how the motor is set in relationship to the transom?

 

[ezeke]

Re: 1992 Johnson Evinrude 120 hp

It takes 10 minutes to check the thermostats, just take the four screws out of the cover at the top of the cylinder head and see if everything is ok. <br /><br />It is a looper and they need to run at the temperature they were designed for or they will foul up. Been there, done that.<br /><br />Costs nothing to check the recirculation check valves. They should only allow one way passage. Just drop the lower cover down, pull the little hoses off, unscrew them, and blow a little carb cleaner each way.<br /><br />If the plug is fouled, so is the whole firing chamber. You cannot fix the whole problem with a spark plug. You have a pretty good shot at it if you de-carb and get the temperature right, though.

 

[marysboats]

Re: 1992 Johnson Evinrude 120 hp

If that engine will run normally for ten minutes, or more. It is not thermostats, check valves, prop. An ignition component is breaking down, or you have a fuel delivery problem. Have you checked for water, or debris in the fuel tank. I would go with an ignition break-down here. You could also have a anti-siphon valve in the fuel tank acting up. You have to check both systems end to end, then you know where you are at.

 

[littlemac]

Re: 1992 Johnson Evinrude 120 hp

I checked the thermostats one did/nt have one at all. the other side had broken spring.I ordered all parts maybe this will cure my problem. I will know by next weekend. Thank you all for your help...........little mac.

 

[marysboats]

Re: 1992 Johnson Evinrude 120 hp

The engine ran good before, and the thermostat was missing then. You say that the compression checks out even. The engine runs for a short time, then starts to die down. A thermostat is not going to cure this problem. Your groping in the dark here.

 

[ezeke]

Re: 1992 Johnson Evinrude 120 hp

Thought you might want to follow this thread: 1991 120HP Thermostats

 

[littlemac]

Re: 1992 Johnson Evinrude 120 hp

what are symtoms if the thermostats are not in....

 

[marysboats]

Re: 1992 Johnson Evinrude 120 hp

It may not idle smoothly, it would have poor throttle response from idle, it could lead to cold siezeing, and piston damage. At wide open throttle you would'nt know the difference.

 

[ezeke]

Re: 1992 Johnson Evinrude 120 hp

These opinions may help the discussion along:<br /><br />“RetNav.... I try not to ever criticize a fellow mechanic; however your mechanic's suggestion about the thermostats does raise some questions.<br />(Thermostat Purpose)<br />Many engines are considered high performance engines and demand a thermostat(s), and many smaller hp engines also require a thermostat for the following reason. The pistons actually distort/twist off round when running. The thermostat is required to keep the outer wall surrounding the steel cylinder, and the cylinder wall itself at a temperature to compensate for the distortion.<br />With the thermostat removed, the difference in temperature between the inside the cylinder and the water jacket quickly reaches a point whereas (in effect) you have a oblong piston running up and down a round cylinder. Bottom line is without the thermostat, the piston and cylinder wall could be damaged in a short period of time.<br />--------------------<br />ReevesJ32@aol.com<br />30+ Years With OMC” -- Joe Reeves speaking of a 1990 200HP Looper without t-stats <br /><br /><br />“The t-stats on that motor are part of the pressure control, it may be one side is stuck open, that motor should idle about 150-160*.at idle it uses water pressure to hold the diaphragms down to keep the stat seated, when the water control valve opens, its connected to the advance lever, it allows the stats to move off the seats as needed. Not only does that engine need lots of water pressure if you don’t have the stats it runs nasty and it’s possible to fry the water cooled regulator.” -- <br />Rodbolt Speaking of 1991 120HP Looper <br /><br />“It may not idle smoothly, it would have poor throttle response from idle, it could lead to cold seizing, and piston damage. At wide open throttle you wouldn’t know the difference.” -- <br />RJohnson Speaking of 1992 120HP Looper without t-stats

 

[littlemac]

Re: 1992 Johnson Evinrude 120 hp

thank you alot for the information when i finally get it running like it suppose to everyone will know what the problem was. I told the mechanic i didn/t want to even look at this boat&motor until it ran like a new one...thanks everyone.....

 

[littlemac]

Re: 1992 Johnson Evinrude 120 hp

I went ahead and tried the motor with the new thermostats. It made it about 200 yards and the alarm went off. The motor was hot. I had to take the thermostats out so I could drive back to the landing. Any suggestions?

 

[ezeke]

Re: 1992 Johnson Evinrude 120 hp

Less than 30 days ago you said this same motor was running at 60 MPH. <br /><br />Now you say it is overheating in 200 Yards. What are you leaving out of this thread? The thermostat didn't do that.<br /><br />When exactly did you perform routine maintenance on your water pump?

 

[littlemac]

Re: 1992 Johnson Evinrude 120 hp

I found out the motor had one thermostat in it and the spring was broken on it. I replaced both thermostats now it over heats within 200 yards.Explain why it runs hot with thermostats in it.

 

[ob]

Re: 1992 Johnson Evinrude 120 hp

Possibly wrong spring application on the t/stat assys.Possible debris in cooling sysytem that flows enough with T/stats out but is restricted to the point of overheat when they're in?Did you find any or all of any broken or missing parts from the original stats or what was left of them?