OVERHEATING? Still pumping water.

ECHOSIDE

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Kinda a newbie to large outboards, but auto mechanic for 16 years now. I was putting around the lake for about an hour and an alarm started to sound by the key. The engine is a 1989 Evinrude 90hp VRO. Now the VRO has been removed and disabled since refurbish was done. The alarm was constant even when the motor was off if key was on. Im assuming this was overheat alarm? Now the engine was still pumping water perfectly, why would this be overheating if its still pumping.

THANX IN ADVANCE JASON
 

Bosunsmate

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Yes thatl be the overheat, Is it still going off now with the engine cool?
It might be a blocked thermostat or one thats failed and is staying shut
 

emdsapmgr

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Probably want to start with the thermostat housing. That engine will still overheat at idle if the incoming cooling water can't get out of the block. (can't circulate) as Boson indicates. One thermostat for each head. If one sticks shut-that's an overheat. Also, the small bleed hole(s) in the thermostat valve body could be restricted. (sand, weeds, etc.- If the warm water can't get to the back of the stat, it can't heat up enough to open.) You may want to test further by renting or borrowing a laser temp gun.
 

racerone

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Water diverters / deflecters out of place.-------Cylinder heads need to come off to inspect those.
 

ECHOSIDE

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What should the temp be at the head i do have a infrared temp gun. Can i run without thermostat like i do with some cars and machinery?

Thanx
 

Bosunsmate

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What should the temp be at the head i do have a infrared temp gun. Can i run without thermostat like i do with some cars and machinery?

Thanx
not sure on temp probably around 173 max
no running without a thermostat will cold seize and carbon it up, it will also idle poorly and starting will be hard
 

ECHOSIDE

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So im waiting for my manual to show up is there any way of confirming or testing the thermostats?
THANX jason
 

emdsapmgr

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The thermostat opens at 143 degrees. Will idle between 143 and maybe 155. That's normal. If it heats to 212, you will get a hot horn. The horn silences when it cools to 175- which is still way too hot for normal operation. You need a stat in order to keep the temp up in the block. As was mentioned, cool running occurs with no stat. That promotes poor combustion, and may cause carbon to accumulate around the pistons rings. So-run stats in that engine.. Since you are working on this engine, you may want to invest in a real factory service manual-see: outboardbooks.com
 
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Fed

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After putting around for an hour before the alarm went off I'd be thinking I picked up a plastic bag or something.

Assuming the VRO alarms have been disconnected properly.
 

ECHOSIDE

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I just got my factory service manual from OMC. Unfortunatly it does not give a trouble shoot for cooling system. I did not pick up anything that's the first thing I checked. I thought the VRO was a intermintant alarm not constant? Is there anything I can do to check if it is thermostats before taking them out?

THANX
 

emdsapmgr

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The factory test for stats is with them removed from the engine. I'd be inclined to do some laser gun temp testing first-before pulling the thermostat housing apart. To see just what temps the two heads are running at idle. Compare the readings as detailed in response #9, above. That will give you some indication if they are working or not. Also, when running on plane, the engine temps will go down up to 20 degrees from normal idle temps-when the pressure relief valves open. That's normal. So you can test idle and planning temps before pulling the stat housing apart. Overheat alarms are constant. VRO (oiling) alarms are intermittent. Since your VRO has been removed, the oiling alarms should be disabled. (not necessary.)
 

emdsapmgr

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Yes. They are actually on the midsection exhaust adapter, not the powerhead. While pretty tricky to remove on the bubble back exhaust 115's. The flatback exhaust model you have is much easier to access.
 

ECHOSIDE

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Ok so I did some temp gun testing today. The right bank is definitely the hot side. The left bank was at about 115 deg. + or -. The right bank was at 160 to 170 deg + or - when I shut it down. The water temp was 48 deg. So thermostats? or what. any help
 

Fed

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When you tested with the gun was that in the water or on the muffs?

FWIW when I was looking for an overheat reason I ran mine on the muffs with the 2 head to thermostat housing hoses disconnected so I could gauge the amount of water flow & feel the water temp.

I was trying to decide between a plastic bag, blocked diverters, blocked head covers or a thermostat problem.

By disconnecting the 2 rubber hoses you by-pass the thermostats completely.
 

ECHOSIDE

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t was in a bucket with cold water filling it. If I disconnect the hoses wont the water fill up the engine housing? Do I block the hoses off or just let them flow?

THANX
 

Fed

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You do realise the water in your bucket has to well & truly cover the water pump, you'd want to be at least 6" above the AV plate.
Could be you weren't getting a full supply of water from the bucket.

I let the water flow, it just sort of disappeared out of various gaps around the pan area.

I suppose if you didn't want to get it wet you could connect a couple of temporary hoses to the heads and let it flow outside the pan, I didn't give it a thought.
 
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