thermostats for johnson 140hp 1991

[boating maniac]

Ok I have a 1991 johnson 140hp, the model number is VJ140LEID. This engine has two thermostats. I replaced both. The engine still runs cold in cold water. Takes twenty 10-15 minutes of cruising before it kicks out of the cold start mode and starts to run nice and smooth. It will even go back into cold start mode where the rpms will go back up to 1500 or so in neutral if you let it idle in gear for a while say idle through a no wake zone for 10 minutes. Don't know why it does this or if it's normal, but I was wondering when installing the thermostats if you screw them in all the way until they seat on the diaphram? This engine has the plastic 140 degree thermostats. I read a post that says that the thermostats are supposed to screw and unscrew themselves to seat and unseat on the diaphrams. I don't know if that person was correct or not. That was a different motor.

 

[boating maniac]

Re: thermostats for johnson 140hp 1991

Basically my question is do you screw the thermostats all the way into the diaphram or do you leave them loosely screwed in?

 

[clanton]

Re: thermostats for johnson 140hp 1991

Screw them all the way in. Look at diagram of hoses and water valve in service manual, if correct engine will warmup.

 

[boating maniac]

Re: thermostats for johnson 140hp 1991

That's the way I have them. The only thing left is the water control valve. I guess the engine is still messed up then.

 

[boating maniac]

Re: thermostats for johnson 140hp 1991

Is it possible that the water control valve could be bad? What is there to go wrong with it? Is that a part I can just put on there. I think someone mentioned that it had to be synchronized.

 

[boobie]

Re: thermostats for johnson 140hp 1991

The water control valve keeps pressure on the thermos so the mtr heats up at idle to about 2000 rpm. If that valve is messed up your mtr won't warm up.

 

[boating maniac]

Re: thermostats for johnson 140hp 1991

it takes about 15-20 minutes of cruising at 3500 rpm for it to kick out of cold start mode where it runs smooth to the point that you can hardly feel it running and the idle goes all the way down. At this point the temp gauge has only moved a tad and it stays at the bottom. The guy at the outboard shop said if it gets out of cold start mode then that's all that matters. But the engine still isn't running at 143 degrees or whatever the thermostat is set at. I need to find a new mechanic. The guy said they don't work on motors as old as mine that often anymore, which I thought was odd cause most of the parts were old carbureted motors! Don't know what their deal is. The place has been their for twenty years.

 

[archcycle]

Re: thermostats for johnson 140hp 1991

I have the thermostats screwed all of the way down on the diaphragms on my 1990 J140.

Did you notice the pinholes in the corners of the diaphragms which match up to the covers? I assume they're there to equalize pressure. Could that have anything to do with it?

 

[clanton]

Re: thermostats for johnson 140hp 1991

There should be a hose/s from the thermostat cover/s to the water control valve. The valve located on starboard side of engine, valve is connected to throttle arm. When idling the valve is closed holding water pressure on the diaphram, which cause the the plastic housing of the thermostat to set on its seat blocking water flow. Somewhere above idle the water control valve will start dumping water pressure allowing the thermostat plastic housing to unseat allowing more water to flow.

Your problem is to much water flow at idle. Caused by bad diaphram in photo of other poster, thermostat seat in cylinder head, leaking hoses to control valve, or control valve broke/leaking.

 

[boating maniac]

Re: thermostats for johnson 140hp 1991

I've replaced every part their is to replace except the water control valve. i replaced the water pump impeller, new thermostats, new seals, and new diaphrams. I took the boat out yesterday and it never got out of cold start mode. It ran rough anytime below 1800rpm. But smoothed out and ran good above that. So my question now is, is this water control valve a part that needs to be synchronized? Somebody on here told me that it needs to be synchronized by the book. I don't know if this is true or not.

 

[clanton]

Re: thermostats for johnson 140hp 1991

I will get you a diagram of the hoses and valve, by late tomorrow. I think the valve is just connected to throttle, if link/sync is correct valve will be correct. At idle there should be very little water flow thru the valve.

You could pinch the hoses from the thermostat housings, stopping the water. temp should go up at idle, overheat at high speed.

 

[clanton]

Re: thermostats for johnson 140hp 1991

There is a different method to make the thermostat, but you should try to get the valve working, unless you want to spend more money.

 

[boating maniac]

Re: thermostats for johnson 140hp 1991

If that's all I have to do is buy and install the new valve then I may be willing to do that. Then after that I'll just assuming, well that's just how they designed it to run. Basically anytime the water is below say 70 degrees or so it never gets all the way up to temp. Right now the water temp is at 60 degrees and the temp gauge doesn't even move. So if that's all I have to do is throw on another valve then i guess i will be willing to spend the 70 bucks for the valve. I already spent like 80 on the thermostat kit and then 100 bucks at the dealer having them remove that stainless thermostat ring that I could never get out myself. If you have a diagram that would be awesome so I could see if the hoses are messed up and where exactly the valve is.

 

[boating maniac]

Re: thermostats for johnson 140hp 1991

Thanks for all your help also.

 

[boobie]

Re: thermostats for johnson 140hp 1991

If you have an OEM factory service manual the diagram for the water control valve hose routing should be in there.

 

[archcycle]

Re: thermostats for johnson 140hp 1991

Instead of throwing $70+ in parts at more guesswork why not throw $71 at a service manual AND a used part? What are the odds of your control valve being bad and this one being bad too and thus leaving it unresolved? You really do need the original factory service manual to work on your motor.

Your genuine factory manual for $35.99 shipped. This is a steal at 35.99:
http://www.ebay.com/itm/1991-OMC-JO...ture&vxp=mtr&hash=item5199db1159#ht_500wt_720

Your used water control valve for $35 shipped:
http://www.ebay.com/itm/Johnson-Evi...Gear&vxp=mtr&hash=item2569beb04d#ht_987wt_703

Buy both of those then consult the OMC factory instructions for installing the replacement part. When you see what's in the factory service manual you won't believe you tried to do anything without one.

 

[boobie]

Re: thermostats for johnson 140hp 1991

Well said Archcycle !!

 

[clanton]

Re: thermostats for johnson 140hp 1991

I have the diagram, but can not down load and post to forum. I can send it to you by PM.

 

[boating maniac]

Re: thermostats for johnson 140hp 1991

That will work. Just PM it. Thanks.