1979 55hp Evinrude water pump issues...

[newfiez]

Hey all,

I have a 1979 Evinrude Model 55975C, that I recently lost the water pump, and as a result, the head gasket (or I believe the gasket blew at the same time). I just replaced the head gasket, thermostat, pressure relief valve and put a new water pump kit in it. When dry running the motor on land (hooked up to the adapter/garden hose), the water was shooting out the water tube (I'm guessing tap water pressure helped here). After a few runs in the lake, I noticed the water was coming out less and less, and now it just dribbles (at all engine speeds). The head is hot to touch, but not unbearable. There is slight suction at the water intake, and the water that is dribbling out is luke warm.
Has anyone seen this happen before, and am I going to run into overheating problems again?

 

[Joe Reeves]

Re: 1979 55hp Evinrude water pump issues...

The thermostat opens up at around 148?, somewhere in that area, so the engine's cylinder head will be somewhat hot to the touch. You should be able to hold you finger on it for a few seconds or so....... also on the large exhaust baffle plate on the side of the powerhead.

When you say "the water was shooting out the water tube."

I assume that you're speaking of the exhaust relief outlets at the rear portion of the engine just below the powerhead? If so.........

(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.

 

[newfiez]

Re: 1979 55hp Evinrude water pump issues...

The tube I'm talking about is the water indicator that comes out of the side cover (which I believe is called the engine exhaust cover). There is only steam exiting the 2 exhaust holes, not water...atleast not all the time. I did replace a new inner exhaust gasket while I had it apart (but that should have nothing to do with it).

 

[James R]

Re: 1979 55hp Evinrude water pump issues...

When you run a motor on the hose the hose is providing the water pressure not the pump. Either the pump is not performing, the tube is not correctly fitted or you have a blockage. Did you ensure that the drive shaft was being rotated clockwise from the top when the new impeller was being fitted. If not the blades could be any old way round and no pumping.

 

[Joe Reeves]

Re: 1979 55hp Evinrude water pump issues...

The side plate you speak of is called the exhaust baffle plate assembly. The hose that is attached there leads to the water telltale outlet, a small plastic fitting that clogs easily.

If shoving a piece of single strand steel wire up that fitting when the engine is running does nothing, I would strongly suggest that you drop the lower unit to inspect/replace the complete water pump assembly.

When running a engine that size on a flushette, always have the water turned on full force.

James..... One could install the impeller backwards and it would create no problems. As soon as the engine cranked over, even one revolution, the impeller blades would face properly.

 

[newfiez]

Re: 1979 55hp Evinrude water pump issues...

I'll give it a try and let you know

 

[newfiez]

Re: 1979 55hp Evinrude water pump issues...

For sure there is nothing in the tube, but I couldn't get past the 90* fitting at the motor. I will remove it tomorrow to see if something is hiding in there. I did notice some watter spitting out of the two holes in the exhaust.

 

[newfiez]

Re: 1979 55hp Evinrude water pump issues...

Problem solved...there must have been something trapped on the engine side of the tube. I put some compressed air in the tube, and what ever was there blew out! I now have no issues (for over a month) with the water system. Thanks for your help guys!