74 Johnyrude Question

[FordMan016]

I myself I'm more knowledgeable in vehicle engines then any other but all are similar with needing air/spark/fuel to run.

Cooling is what im wondering about since in a vehicle the thermo. opens when engine get to temp to cool engine.

with a outboard is that the same deal?

1974 Johnson 6hp
mine was not pumping very much then not at all when test running but ran perfect other than that

 

[F_R]

Re: 74 Johnyrude Question

I myself I'm more knowledgeable in vehicle engines then any other but all are similar with needing air/spark/fuel to run.

Cooling is what im wondering about since in a vehicle the thermo. opens when engine get to temp to cool engine.

with a outboard is that the same deal?

1974 Johnson 6hp
mine was not pumping very much then not at all when test running but ran perfect other than that

There are two water flow routes through the 6hp powerhead.

The first route is through the exhaust covers, through the cylinder head (the vertical tube past the spark plugs) and discharged out with the exhaust. This route flows any time the engine is running.

The second route is around the cylinders and edges of the cylinder head. This flow is presented to the thermostat, and a small amount bypasses the 'stat, but most of it is held back till the 'stat opens. Then the second flow also goes out with the exhaust, along with the first flow which, as I said, is any time it is running. The second flow comes and goes according to the temperature, but you can't tell.

Bottom line is, there is always a water discharge. You really don't know what route it is taking, nor should you worry about it unless it is plugged up or something and overheating.

 

[Joe Reeves]

Re: 74 Johnyrude Question

The thermostat on a outboard serves the cooling scenario but also has another function.

When the outboard is running, the piston/cylinder match distorts (piston/sleeve). The thermostat has the water running thru the external portion of the sleeve area to compensate (correct) that distortion problem. Removing the thermostat results in having a mismatched alumium piston running up and down that steel cylinder wall.