78 Evinrude 115 thermostat

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ken_kaniff

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Re: 78 Evinrude 115 thermostat

I'm assuming the thermostat sits right below the power head? is that correct?
 
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rockyrude

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Re: 78 Evinrude 115 thermostat

A model number would go a long way in getting you the correct answer, but I'd also check the temp switch on the head. If the alarm is sounding when the motor is cold, the switch would be my first guess. The thermostat is at the rear where the two hoses are. If you want to go after the thermostat, you need to drop the "pan" the cowl is attached to to get access to the thermostat.
 
iwombat

iwombat

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Re: 78 Evinrude 115 thermostat

Sounds like your switch or switch wire is grounding. Check the temperature of the motor when the buzzer goes off. If it's within spec it's the switch.
 
iwombat

iwombat

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Re: 78 Evinrude 115 thermostat

Those switches are about $50 and you've probably got two - one in each head. It's just as likely to be a bad wire as a switch though, or even a bad buzzer. Turn the ignition on and start jiggling the wire harness around and see if you can get the buzzer to go. Likewise, if the buzzer is going try and disconnect the switch at the head (there's a connector under a rubber boot) and see if the buzzer stops.
 
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emdsapmgr

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Re: 78 Evinrude 115 thermostat

Your engine is a flatback model, so access to the thermostat housing is not so bad. I have a 79 85 hp and do not need to pull the powerhead to get into the thermostat housing. You should be ok. If it is tight, you can loosen the lower cowling pan (tray) as rockyrude indicated and it will move downward an inch or so, permitting better access to the thermostat housing.
 
iwombat

iwombat

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Re: 78 Evinrude 115 thermostat

I guess I'm not sure why you're even going after the t-stats at this point. I thought we'd isolated it to something electrical.
 
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emdsapmgr

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Re: 78 Evinrude 115 thermostat

Two things that may help you. You can look at factory exploded parts diagrams online at: epc.brp.com. You can see how it goes together from these diagrams. You can get an original factory service manual from Ken Cook, in Milwaukee. You can call them or contact them on line. The factory manual is the best to help you when working on the engine.
 
iwombat

iwombat

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Re: 78 Evinrude 115 thermostat

The way the overheat sensors work is that they ground out to the block when they get too hot. The buzzer is powered off the ignition circuit in the remote and when ground contact occurs in the sensor it goes off. If the leads from the sensors are shorting anywhere it'll trip the buzzer as well.

Next time the buzzer goes off, just disconnect the sensors (they're in the head and have a brown wire) at the connector near the heads. I think you have one on each side, but some models only had a sensor on one side. If the buzzer still sounds after disconnecting the sensor, then it's either the brown wire or your buzzer that's malfunctioning.

If your buzzer is sounding, and you're certain the block isn't getting too hot, then replacing the thermostats will not fix your problem.
 
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ken_kaniff

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Re: 78 Evinrude 115 thermostat

took the boat out all day on sunday. Put in around 9 took out around 8 pm. The buzzer did not go off at all. Everything seemed to work great, although at times it didn't want to start. I think this will be worked out with use, although I am buying a second battery just to be safe. I already carry a portable jump starter. I don't worry that it won't start, just that the battery could be drained before it starts.
 
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