1975 70hp water jacket plugged?

[kds13007]

hows it going first post on this forum. i recently purchase a 1975 70 hp evinrude and have been trying to get it started. i got the motor running and put the ears on the water intake and saw almost no water leaving what i believe to be the water ejection ports (just a fine mistif that). i just replaced the water pump so that shouldn't be the problem, i was wondering if the cause of my problems is deposits in the water jacket not allowing for the water to p*** and is there anyway to clean out the system with out taking it all apart

[Joe Reeves]

That engine didn't have the small plastic water outlet telltale fitting so I a$$ume that you're speaking of water not exiting the two holes at the top of the long exhaust housing (see the explanation below).

Also, be advised that when running ahigh hp engine on a flushette, the water must be turned on full last.

(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 (different 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.

[kds13007]

*** this was the exact explanation I needed for my engine. You were correct there is no telltale water outlet so the small amount of exhaust and water coming out was probably from having the engine idling. One follow up question should there be water coming out of the backside of the exhaust housing?

[Joe Reeves]

Originally posted by kds13007 View Post

One follow up question should there be water coming out of the backside of the exhaust housing?

Are you speaking of the exhaust housing large plate on the port side of the engine... OR... the long exhaust housing between the powerhead and the lower unit?

As it stands, I have no idea of the exact spot you're speaking of.

Also, are you saying that water is exiting there... OR... that you think water should exit there and it is not?

[kds13007]

Not entirely sure the name of the part but I can describe where it is. When the motor is down there is a seam in the exhaust casing about an inch or two below the edge of the mounting bracket. I don't believe water should be coming out of this area. would it be helpful if I attached photos of the area I'm talking about

[Joe Reeves]

Yes, a photo would be a big help.

[kds13007]

I'll post them soon

[kds13007]

well if i did this right i should have an attachment with an image of the motor and the area i was referring to circled in red. when it is running water sprays from a whole in that area as well as a couple of joints in the metal. could this be casued by a bad connection from the water pump to the water tube or a poor gasket in the exhaust inner housing.

[Joe Reeves]

That's a water outlet to prevent water from flowing up the driveshaft tube towards the lower crankshaft seal. Don't be concerned about it.