b79 Johnson 100 cooling questions

[Michael Weller]

" How does it work? I know th

" How does it work? I know the water pump pushes water throught the heads, but how? Which direction is water flowing through the two hoses connected to the thermostat housing and the exhaust ports on the heads? Does water come from the pump through the thermostat housing into the heads and then out the pee hole? Why are there 4 holes in the thermostat housing?

I question b/c my motor isn't peeing correctly. A couple of you got me through replacing the impeller, but still no luck. I thought the thermostats might be stuck, but they have already been removed. W/ the thermo housing removed, I put the hose up to the pee hole to see if I could see where water comes out, Not knowing if to expect to see it come from the exhaust ports or the therm. housing, but I never saw any water at all. Is there a blockage somewhere? Why isn't this motor peeing correctly? Please help...I can't find a mechanic who will work on a '79 (too old they say).

??????????????????confused!!!!!!!!!!!!!!!!! "

 

[joereeves]

"Michael.... Without going tho

"Michael.... Without going thoroughly into the water cooling system, the water leaves the water pump, goes up that water tube into the powerhead, heads first for the exhaust cooling area where the water outlet hose/elbow is for the water telltale outlet. The water circulates through the cylinder heads, and then goes into the hoses leading to the thermostat area.

That engine is not to be run without thermostats! It must run at a certain temperture or piston damage will absolutely result! Also, without the thermostats, there is no back pressure at various points that the engine demands. This lack of backpressure will also affect the force of the stream exiting the water telltale outlet.

Replace the thermostats first and make sure the water bypass valves/seats/springs are also installed. Then if you haven't already, remove and clean that plastic water telltale outlet.

After doing the above, if you still do not have water exiting that telltale outlet with a strong force, I'd suggest you reinspect the water pump.

Joe

"

 

[Michael Weller]

" Thanks Joe. Do you sell the

" Thanks Joe. Do you sell these parts? There is nothing in that housing...not thermostats, no valves...I need to find someone who can get me the right parts, and if possible so I can get out this weekend. I really would hate to spend my whole day off w/ my boat in the driveway!

If this condition causes piston damage, I fear that damage has been done. It appears to me that this has been the condition for some time...as in years. I don't know though, cause it seems to run pretty strong.

Would this create a scenario where it pees ok at higher rpms? Because that's what's happening.

Thanks so much for helping Joe...your time does not go unappreciated! "

 

[Michael Weller]

" In addition....
That makes

" In addition....
That makes sense that at lower rpms, w/o the valves/tstats that the water wouldn't be forced out the tell-tale port. Right? It would just exit through the bypass ports... "

 

[joereeves]

"Mike.... Sorry, I don't h

"Mike.... Sorry, I don't have those parts. Your local dealer should have the thermostats in stock, possibly even NAPA. The bypass valve assys might be available through any outboard dealer who would have some old engines laying around that are being used for parts.

The piston damage thing..... you may be one of the lucky ones (it happens). If the compression is in the range of 100+ psi and even on all cylinders, I wouldn't be concerned about it.

Joe

"