1977 evinrude 85 questions HELP PLEASE

[BradWhitehead]

Ok i have a 1977 evinrude 85. I have had the boat for aobut 8 years now. When i got it it ran like a dream and had zero prolems. Recently i let some family use it for the summer since i was away on business. I was going to take it out this weekend and was tuning it up and checking it out. Since this model does not have a tell tale on it ive always looked at the exhaust with the muffs on it to tell if the impeller was working. I noticed the exhaust coming out of the prop was only finely misting water. The two exhaust ports higher on the lower unit are not putting any water out. I couldnt decide if the impeller was working or not so i broke down and put a tell tale on it as described on these forums (by the way thanks alot). I cranked it and there was no water coming out of the tube. My questions are what are the two hoses coming off of the back of the bottom two cylinders that go into the lower unit. Are these water hoses or exhaust or something like that. My second question is how much water should be coming out of the prop and how much out of the top two exhaust ports on the lower unit. I also noticed when i tried to crank it up for the first time this year it would only run for about a minute or two on cold start and then it would just go dead. It did this a little last year but when i have it in the water i just pull the cold start and before it goes dead put it in gear and take off. After i stop it cranks right up and runs fine, or atleast it did last year. This is not a major concern but thanks if you could provide this info also. My main questions are above> any and all suggestions and coments are welcome. Thanks

 

[Joe Reeves]

Re: 1977 evinrude 85 questions HELP PLEASE

The slots/holes to the rear of the lower unit, just above the cavitation plate are water outlets for the thermostat flow..... when the thermostat opens.

The two holes at the top rear portion of the long exhaust housing are described as follows:

(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.

Time to install a new water pump assembly.

The die out when cold problem....... Usually due to a fouling carburetor. Time to clean and rebuild them.