1969 Johnson 85 hp cooling system questions

[Silly Seville]

Guys,

Before anyone suggests I get an OEM service manual...I have one on the way!

85ESL69E It starts, runs and idles nice and smooth. Electric shift works just as it should. I am mostly a happy camper. Last issue to tackle is the cooling system. Yes, I have read many threads about this, and yes, I have looked at the parts diagram. Yes, I have put a brand new water pump kit in it, and installed it correctly. I've done near a dozen water pumps on Mercruiser sterndrives, so I'm not new to that game.

Here is my specific issue that I would like to address with your collective help. The water is not getting past the thermostat/vernatherm apparently, as I have taken off the rotten cylinder head hoses, and there isn't a drop of water in the hoses, exits of the thermostat housing or the entrance to the heads. I have the lower unit submerged in a tub of water, so I know that isn't the problem. I have idled the engine until the heads were 165 degrees according to my infrared thermometer.

What temperature does it take to open the vernatherm?
Does it have a bypass that always allows SOME water to pass, or is it an off/on design only?
Does the vernatherm function just like a thermostat? Can it corrode and stick closed?

I'm asking these questions before I yank the thermostat off, since I know I will need several gaskets once I do that.

Final question: If I do tear into the thermostat housing and the vernatherm or the valves are indeed the culprit, can I just run without them; i.e. a wide open cooling system?

Thanks for your answers in advance!

 

[Joe Reeves]

Re: 1969 Johnson 85 hp cooling system questions

Here is my specific issue that I would like to address with your collective help. The water is not getting past the thermostat/vernatherm apparently, as I have taken off the rotten cylinder head hoses, and there isn't a drop of water in the hoses, exits of the thermostat housing or the entrance to the heads. I have the lower unit submerged in a tub of water, so I know that isn't the problem. I have idled the engine until the heads were 165 degrees according to my infrared thermometer.What temperature does it take to open the vernathermDoes the vernatherm function just like a thermostat? Can it corrode and stick closed? If I do tear into the thermostat housing and the vernatherm or the valves are indeed the culprit, can I just run without them?

You are thinking backwards.... The water DOES NOT travel to the vernatherm and then to the heads... the water travels to the block first, then to the heads, then to the vernatherm. I suspect that you do not have the lower unit submerged deep enough into the water to cover the water pump.

If the pump was functioning properly, water would be shooting out those hoses when you removed them from the cylinder heads. The water pump is not a self priming pump and must be submerged. Check to make sure that the water's surface is at least a couple inches above the water pump. If it is and the pump is still not functioning, I'd suspect that one of the copper water tubes was missaligned when the lower unit was installed and shoved upwards instead of being inserted within the water pump tube grommet.

The vernatherm is actually a thermostat by a different name and normally opens somewhere around 148 degrees, hence the engine would be running slightly higher than that. Notice the holes/slots just above and to the rear of the cavitation plate... those are the vernatherm/thermostat water outlets. Water will only exist at that area when the thermostat opens.

The engine demands that it be run with a thermostat present, otherwise piston and cylinder wall damage will take place in time.

 

[Silly Seville]

Re: 1969 Johnson 85 hp cooling system questions

Wow...Thank you Joe! I have just learned something very important. I'm glad I didn't disassemble the thermostat housing. What is the point of a thermostat if cold lake water is going to immediately course through the block anyway? I knew a 2-stroke was going to be different in the obvious ways (combustion cycles and no forced lubrication) but I just can't wrap my mind around the cooling system pathway.

I have the water line about an inch above the intakes. That isn't enough, is it?

 

[Bosunsmate]

Re: 1969 Johnson 85 hp cooling system questions

You need it much more than an inch. More like 6

 

[Silly Seville]

Re: 1969 Johnson 85 hp cooling system questions

Ok...well I guess that means I just finished destroying a brand new impeller since I've run the engine for a total of about three minutes. My only saving grace may be that I had put lots of assembly lube in the cup when I installed the impeller. Maybe that, and the bitter cold outside saved the impeller vanes. I have a pair of water muffs, just didn't want to use the hose outside while below freezing temps. :facepalm:

 

[Joe Reeves]

Re: 1969 Johnson 85 hp cooling system questions

Wow...Thank you Joe! I have just learned something very important. I'm glad I didn't disassemble the thermostat housing. What is the point of a thermostat if cold lake water is going to immediately course through the block anyway? I knew a 2-stroke was going to be different in the obvious ways (combustion cycles and no forced lubrication) but I just can't wrap my mind around the cooling system pathway.

I have the water line about an inch above the intakes. That isn't enough, is it?

The cooling system is similar to your automobile or truck. Water DOES NOT flow thru the 4 cycle vehicle's block until it reaches a certain temperature, then the thermostat opens and allow the water to flow past the thermostat into the top of the vehicles radiator.

Same holds true for the 2 cycle outboard. Water does not course thru the block... it is stopped by the thermostat unless the thermostat is in the open mode. The exception is that the bypass valve will allow a flow to exist if the rpm increase to a certain point.

A inch above the water intakes? No.... I said that the pump is not self priming. The water intakes are below the water pump and as such, the pump would simply draw air. You need the water level to be above the water pump by at least 2 inches.

 

[boobie]

Re: 1969 Johnson 85 hp cooling system questions

Back the boat in the lake once and see what happens. That's the normal level it runs.

 

[Silly Seville]

Re: 1969 Johnson 85 hp cooling system questions

UPDATE:

Good news Guys, she works great!

After soaking the garden hose in a bathtub of hot water for an hour, I was able to put the muffs on it and get it to circulate water. I don't know if the thermostat ever opened because the heads wouldn't get above 80 degrees since the water and outside air were so cold...but I got the idle adjusted nice and low, and water was shooting out the prop with the exhaust and several times it was spitting from the two exhaust relief holes. I may have not given it a chance to warm all the way up in just 5 minutes, since I ran out of premix and it was getting late, but it was running without choke and not smoking near as bad as it was in the beginning.

Thanks for all your help!

 

[boobie]

Re: 1969 Johnson 85 hp cooling system questions

The true test will be when you get it in the lake.

 

[Silly Seville]

Re: 1969 Johnson 85 hp cooling system questions

The true test will be when you get it in the lake.

That could be 6 months from now, since I don't even have a boat to mount it on!

 

[Joe Reeves]

Re: 1969 Johnson 85 hp cooling system questions

Just strap it on your back and hold on tight!

 

[boobie]

Re: 1969 Johnson 85 hp cooling system questions

Put on a pair of water skis first.:laugh: