Overheating 1977 Evinrude 85HP

I put in a new water pump about 3 weeks ago. It ran okay and the cylinders were cool to the touch after serveral minutes. I changed to a new prop from a 13x19 to 13 3/8 x 17 to get out of the hole better to pull grandkids. This may not have caused the problem.

First day out ran great. Second day suddenly lost 3/4 of the power and the flywheel was really hot. We eased back to the dock about a mile with the reduced power.

I took it out today and it ran ok for about 5 min then lost the power and the flywheel and cylinders were real hot.

How do I check the waterpump with water mufflers? I had a terrible time putting the lower unit back on and gave up and hired someone for $150. So I was hoping to check without removing the lower unit again. I am 67 and don't have the strengh to do it.

Can I disconnect the hose coming out of the cylinders and test?. There are two of them.

Re: Overheating 1977 Evinrude 85HP

The telltale did not come out till the 1978 model year, so it is somewhat difficult to determine the condition of the water flowing thru the block on that engine. You have two thermostats on that engine. Each controls the water outflow from one half of the block. (each controls the temp in one head.) If the stats do not open properly, the engine can overheat at idle. (no water can excape out of the block, causing a quick overheat.) It is a good test to remove the two hoses which go from the head to the thermostat housing. If you have good water flow from each, likely the impeller is ok. I'd have a look inside the thermostat housing and probably replace both stats. Check for sand or other debris inside the housing. There are two pressure relief valves inside the housing also. They open when the boat is planing and provide much more cooling water flow in addition to that which comes thru the stats. Check those nylon valves to make sure they are not heat deformed and that the rubber seats are ok. You should also be able to determine when the stats open. Start the engine when cold. Hold your hand behind the two exhaust relief ports at the top of the midsection. After about a minute, the stats will open and you will get water droplets coming out of the ports-forming on your hand.

Re: Overheating 1977 Evinrude 85HP

I purchased a themo-gun at Lowe's for less than $20. The temp is 105 to 107 everwhere I checked. I checed the Flywheel, next to the spark plugs, water at the prop and all were in that range.

It hicups about ever 5seconds and blue smoke comes out the exhaust when it does. I rebuilt the carbs about 3 weeks ago and it ran but even then it had the hicups. Could it be the coils? All the plugs were new, now they all are a dark tea color.

Re: Overheating 1977 Evinrude 85HP

Sounds like the engine is running cold. The stats will open at 143 degrees, so your current temps are pretty low at idle. I don't know if you have been into the thermostat housing, but you may want to consider replacing the stats-they may be stuck open. You want more heat out of the powerhead to keep carbon buildup at a minimum as you run the engine and for good fuel economy. The hiccups you refer to are probably a lean sneeze. That's a carb issue, not ignition. If the small, dedicated idle passages in the carb have any dried fuel restricting them, they won't flow fuel and the engine will occasionally miss at idle. That miss usually goes away as soon as you open the throttle and the engine starts to draw extra fuel from the high speed jets.

Re: Overheating 1977 Evinrude 85HP

Is this where the sats are located?

Re: Overheating 1977 Evinrude 85HP

This does not appear to be the thermostat housing for a 1977. The 77 housing is longer (wider) than this one pictured. This one looks more like the older style housing, used up through 1976. This housing should have only one stat, called a vernatherm. I believe the vernatherms ran somewhat lower temps than the dual stat setup, which would explan some of your lower temp readings. Still may be worthwhile to replace that vernatherm and visually check inside, since it may be running cold.

Re: Overheating 1977 Evinrude 85HP

I have the same motor and the thermostat housing looks like this. Also my service manual and parts list look the same and it's the vernatherm setup. I wonder if '77 was a 'crossover' year as I think the XL model t'stats are different.