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78 Evinrude 85hp overheating

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Bucksevinrude

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First, I bought this engine new in 1978 and it only has maybe 75-100 total hours, if that, on this engine. Actually it still looks almost new. While it has set for most of its life I have occasionally operated it on my bassboat and have always maintained, serviced, and winterized. About three years ago I replaced the impeller and operated the boat a few times over the season and it runs like a charm. It sat idle since other than running it with muffs a time or two to clear out the carbs. Now I've decided to sell the boat and upon starting the overheat alarm buzzer went off. The sight stream was running strong but I thought I'd just replace the impeller again since I did it successfully once. Nada.....alarm buzzer still goes off. So I thought the next logical step was the crossover thermostat kit. The original 1978 thermostats actually appeared ok although there was some corrosion on one of them. Short story....after thoroughly cleaning and blowing out visible corrosion and replacing the thermostats the alarm buzzer is still going off. I've blown compressed air through the engine block and can feel it coming out the other side, no corrosion or blockage.....the sight stream is strong however it will be cold one second and very hot the next. The one thing I seem to remember that is different now is it seems I recalled seeing water coming out of the exhaust ports before......now there is nothing but exhaust. My question.....what other reason(s) other than the impeller and thermostats could cause overheating? Blockage?....such as not enough water in the pickup tube? It has never overheated before while using muffs. Any advice is very much appreciated.
 

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Thanks, Boobie for the response.....could you explain how to evaluate that and what the solution is? While I'm decent at basic mechanical skills such as replacing the impeller, etc., I am not a outboard mechanic however if steered in the right direction I can generally figure it out. Thanks for any info.
 
Have you checked the temp sensors? I think the 85 is a v4 so it should have a sensor in each head. You can just measure to see if there is continuity to ground. You could also have a short to ground in wire up to the horn. I've seen one that actually shorted the sensor wire inside the remote control box. There is a little horn in the control box that has engine power on one side and the other side goes to ground when hot thru the sensors in each head. You'll see a wire coming out of the outboard side of each head. This usually goes into a rubber cover that seals up the connector. This just slides off, maybe with a little wiggling... worst case you can use a pin type meter lead an pierce the insulation. With the switch off just measure to ground on the sensor wire. If you see continuity to ground, you can unconnect the sensor and see which direction it is grounded. It sounds like you are getting an alarm even when the motor couldn't be hot.

Next thing. the water coming out of the ports in the back. I've seen this a couple times. Especially after someone puts muffs on and turns the water on too hard. In the top of the water pump there is a seal to the cooling tube. The pump has about a 3/4 in output and the cooling tube to the motor is about 1/2 in. The seal is in that hole in the top of the water pump. If you replaced the impeller you know what I'm talking about. If you pump water in with muffs too hard, it can push that seal up the cooling tube and basically you loose the seal on the pump to the motor. The water pump is pumping water in the cavity along the exhaust tube until it fills up the center section. This can make the motor hot too since it isn't getting enough coolant. You might get enough water to pass the pee test but not enough to cool the motor. Just a couple thoughts. Good luck with that shift linkage bolt...
 
Thanks, applegam1 for a lot of good info. At this point I'm thinking the alarm buzzer is functioning correctly as it takes 4-5 minutes before going off. I will definitely check the sensors and any potential short to ground. Tell me about that dang shift linkage.......geezzzzz.....what a pain! I did get kinda good at it last time as it only took about 45 minutes to get it to line up....lol.

A question I have......can anyone give me the torque specs for the head bolts? I'm going to replace the water deflectors and head gaskets next.
 
Hi. If i look at my old manual i get 18-20 ft.lb for the heads.

As a suggestion you may also want to remove the cylinder head covers and confirm those passages are clear. Go slow as these little bolts like to snap off. I had similar problems on a 81 90Hp with a lot more hours. See my posts for info that might help.
 
the water coming out of the ports in the back. I've seen this a couple times. Especially after someone puts muffs on and turns the water on too hard.
Click to expand...
You would need some really good muffs and strong street pressure to see this happen!!!Water only exits these ports when t-stats and poppet valves open....
The pump has about a 3/4 in output and the cooling tube to the motor is about 1/2 in. The seal is in that hole in the top of the water pump. If you replaced the impeller you know what I'm talking about. If you pump water in with muffs too hard, it can push that seal up the cooling tube and basically you loose the seal on the pump to the motor
Click to expand...
Cant happen......
 
I have a 78 Johnson 85 horse with the alarm going off after 60 seconds of full throttle. I had a new water pump kit installed and have removed the thermostats. I have a new thermostat kit to install but read that it was ok to temporarily run it open.
The problem is that the alarm goes off after running wide open for any length of time. I believe the alarm is working properly and not defective or shorting out. Just wondering what to dismantle next? Why this common problem with this V4?
 
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