Johnson 120 v4 Looper, 1985, J120tlcos

[GeeTee]

Hi Guys - i have just recovered from a mid lower unit leak - where the powerhead meets the mid unit housing. New gasket etc. While i was at it i replaced the head gaskets, torqued the bolts, no leaks. When i run the engine i get a strong water stream from the pisser however, the starboard head gets extremely hot. The port head is cool - i can put my hand on it no problem, starboard not so much. I get no overheat alarm but can tell the head is hotter than what it should be. I have removed the thermostats and completely swapped them around, port thermostat to starboard and vice versa. Same problem. Its gets pretty hot pretty quickly, around 3-5mins and this is at idle.

Do i have water restriction or is there somewhere else i can look?

No ive not done a compression test, do i need to?

 

[boobie]

Did you run it with the thermostats removed ??

 

[GeeTee]

No i havent - guessing it`ll run cold then to verify whether or not the thermostats are working?

 

[GeeTee]

Boobie - took the thermostats out and tested them in very hot water, they opened so i can confirm they work. I put only the one back that i knew i was not having an issue with, the stbd head i left the thermostat out of. I ran the motor again and both heads stayed cool, the stbd without the thermostat actually ran cooler. Awesome. Given the above i can confirm that i don't have a blockage somewhere lower down and that i`m getting enough water to the heads which is great. So, while at idle or under 2000rpm i believe the water control valve is supposed to stay open allowing water to move into the stbd head through the diaphragm weep hole in the thermostat housing. Then, once the head is full of water it will spill over into the port side head cooling it. This did not happen. So while at idle i was not getting any water coming from the control valve into the thermostat housing.

I removed the water control valve, cleaned it and blew through it - didnt seem to have any issues. I did notice however that when i blew through it and it was at the throttle idle position it restricted more water going into it. When the valve was opened or accelerator was moved forward it allowed more water through. I think this is the way its supposed to work?

Anycase, still not sure if the control valve is working correctly. Tomorrow i`m going to bypass the control valve completely and see if the head stays cool while idling.

Any other ideas as to where my problem could lie?

 

[Faztbullet]

Change the diaphragms that the t-stats screw into.....the one thats cool is the bad one.

 

[GeeTee]

Fatz - Wow - i would never have guessed that, considering your experience i`m going to place an order for the diaphragms now, its a cheap fix. If you don't mind can you explain to me my why you`re saying the cold running head has a faulty diaphragm? How do you come to this conclusion?

 

[Faztbullet]

The water control valve shuts the water off to t-stat diaphrams and only water thru jackets are from t-stats slits and jackets run nearly dry on these models. When water control is opened with throttle the t-stats will come off the seats for full flow and jacket cools down.

 

[GeeTee]

So you`re saying that at idle i should not be getting any water going to the thermostat diaphragms from the water control valve? Only when the throttle is activated does water pressure push water through the slits in the diaphragms in the jacket in the head. How much water can really get through these slits?

Here is a link to the motor running showing that there is no water coming out of the control valve which is going to the stbd thermostat cover. you`re saying this will only increase if i throttle up? My question still is why is the cold running diaphragm faulty? Are you saying that the water is not going thorough the slit that it might be worn?

Youtube link - https://www.youtube.com/watch?v=47pSZmYi2Pw

 

[Strangeleak]

No Title

Maybe the internal part of the valve is installed 180? out or there is a blockage.

 

[GeeTee]

Strangeleak - thanks for the photo - not sure why my manual doesn't have that - mine is definitely configured like that so its right. Also, all the orifices are clean. Are we in agreement that i should be getting alot more water pressure from the control valve below 2000rpm or at idle?

 

[Strangeleak]

I remember reading in another post that you have a Seloc manual. This picture is from a factory OMC Manual.

From your video it appears you are get NO water pressure at all. So yes, you should be getting a lot more pressure.

What I meant by "installed 180? out" is the internals of that valve can be installed in the complete opposite orientation than it's designed to function.

Remove the valve from the engine and blow through the lower port while the lever is in the idle position. If air does not come out of the nipple that goes to the thermostat diaphragms, then carefully take the center section of the valve out and turn it 180? and retest.

 

[GeeTee]

Ok, so i decided that i was stuck with either thermostat or water control valve issues - i ordered new diaphragms, thermostats and a water control valve. In the interim i bypassed the thermostats and went fishing. Got the boat off the trailer, engaged the throttle and heard a dreadful loud knocking sound and remembered this was the reason i pulled the boat from the dock in the first place. I had since run it on muffs and with it not being under load or in gear it performed fine. As soon as i put load on the motor this "noise" showed up. I can rev it up in neutral while in the water, sounds pretty good too. Compression is 120ish on all cylinders. Some links to the motor running on the bayou today.

http://youtu.be/TCSKdhhzGpI

http://youtu.be/cbEUwMcjzmE

 

[Strangeleak]

Kinda hard to tell in a video, just sounds like a misfire. Does it still perform well or have you not pushed it beyond the "noise".

 

[GeeTee]

I have not pushed it beyond the noise - it does however rev and sound great when its in neutral, so when it has no load there is no loud noise. I`m going to put it into a large drum and run it again, see if i can isolate where the noise is coming from. Also, at idle speed merely in gear it sounded good.