"The engine has a warning horn
"The engine has a warning horn that should sound off before the engine is hot enough to do any damage, as follows.
(Testing Warning Horn)
(J. Reeves)
On VRO equipped engines where the VRO automatic fuel/oil setup is still being used, make sure that all components are connected as required. This would include the VRO pump wiring harness itself, the oil tank wiring, the overheat sensor(s), and if so equipped.... the vacuum switch that is standard to many V6 & V8 engines.
If the VRO automatic setup has been eliminated and has been disconnected properly, and the fuel and oil is being premixed, make sure that the overheat sensors are still connected, and the vacuum switch if the engine is so equipped.
On engines prior to 1984 which have no VRO setup, ignore the instructions pertaining to the VRO components, etc above.
Turn the key to the ON position (Engine Not Running). Find the TAN wire at the cylinder head(s), then ground out the portion of that wire that is part of the engine wiring harness. If that Tan wire connector has the knife type connector where as it is exposed simply by sliding the rubber insulator back, it does not need to be disconnected.
Grounding that TAN wire should cause the horn to sound. If it does not, find out why as that's the only warning you'll receive should the engine overheat or have some portion of the VRO system fail, or have the engine encounter a fuel retsriction if it is equipped with a vacuum switch.
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That engine, unfortunately, does not have a water outlet telltale. One can be installed but the instructions will need to come from someone else.
Just above and to the rear portion of the cavitation plate (plate just above the propeller) are a few holes/slots. Water will flow out of them when the thermostat opens but not before.
The two holes at the rear of the engine and just below the powerhead are exhaust relief holes. Water usually flows out of them when the engine is in the water (or a tank/barrel) but not all engines have water exiting there when on a flushette.
On a flushette, the majority of the water is flowing out the center portion of the propeller.
(Exhaust Relief Ports - Exhaust Housing (Inner/Outer)
(J Reeves)
The long housing between the powerhead and the lower unit is called the exhaust housing. There is a inner housing within it that has a heavy duty seal around the bottom of it, or heavy duty seals around a inner extension between the housing and the lower unit.
The red hot exhaust travels down thru that inner tube and out the propeller with a somewhat supply of water to cool the propeller hub. A good amount of water surrounds and fills the space between the outer and inner tube, otherwise the outer housing would get so hot that the paint would burn off.
Some water pumps, for some reason (differing even when new) exert a great amount of water pressure, and if the exhaust housing seals are in perfect condition, the water fills the tube to a point of overflowing.
This brings into play those two holes or slots, whichever the engine might have, at the top rear portion of the exhaust housing just below the powerhead.
Now, if those two holes/slots weren't there, water would continue to flow up into the cylinders. Water not flowing out of those holes is no concern for alarm UNLESS that outer housing suddenly becomes extremely hot..... the warning horn should sound long before that happens.
The main reason for those holes being there (exhaust relief holes) is that when at an idle, there is an extreme amount of resistance encountered by the exhaust trying to escape due the fact that the outlet via the propeller is now blocked by a wall of water. The escape route in this case is for the exhaust to escape out those two holes, otherwise the engine would slow down quite quickly and die. If exhaust cannot escape, air/fuel cannot gain entrance to the engine.
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The large plate between the cylinder heads is a exhaust baffle plate, actually two plates exist there. Water is on one side of the plate and red hot exhaust on thre other side. It does get fairly hot when in normal mode BUT if a water pressure problem exists, it will get so hot that it will be impossible to touch it. This plate pretty will well tell you if if the engine is running too hot. BUT check that waring horn."
