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40HP 1971 Johnson Outdrive OverheatingPlease help

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chuck27

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"Hi, fist time boat owner! 197

"Hi, fist time boat owner! 1971 40HP Johnson MOD # 40E71G. Engine overheating while testing with both hose and later in large tub. I followed online instructions and here is what I've done so far: Replaced needle and seat in carb, installed water pump kit,replaced soloneid, checked pressure to make sure the gasket wasn't blown,checked OK.This engine is just not pumping,had at running this mornig submerged in large tub,a lot of water motion water "seems" to get in up to a certain point, but no water out of exhaust.Engine ran,got hot and then started knocking or made a sound similir to someone tapping metal on metal.Shut it off restarted couple of hrs later, still overheating,shut it off and at this point I'm "lost" I don't know what else to check. Please help.Thank you"
 
"In a barrel, the water must b

"In a barrel, the water must be about 3" above where the top lower unit surface bolts up to the long exhaust housing, submerging the water pump.

Drop the lower unit again. You've either had the water pump key slide out of the impeller.... OR one of the water tubes has grabbed the side of the rubber grommet and folded it over. This would effectively create a shut off valve.

Another common problem is a slightly blown head gasket (have you checked compression?). This would allow the combustion to enter the water passageway which would create a stalemate with the upcoming water pressure."
 
"gday mate,just read your post

"gday mate,just read your post.I had the exact same problem on my 35hp johnson 78 mod,it broke my b...s for months,put a complete knew water pump kit through it,knew thermostat and to no avail,i literally went mad and didnt no what to do.Do yourself a favour and replace the cylinder head gaskit,thermostat.The problem i found was my head gaskit was upside down and the plastic impeller key had snapped....Hope this helps"
 
"Joe, will drop unit again and

"Joe, will drop unit again and follow your suggestion.I did test compression and seems ok, any chance that gasket is blown even though there is compression?What should correct reading be?Thank you very much for your help"
 
"Compression is usually 100&#4

"Compression is usually 100+ psi and close to even on both cylinders. What readings are you getting?

A slightly blown head gasket would allow the combustion to enter the water passages creating a stalemate with the upcoming water pressure.

A head gasket blown moreso would allow water to enter the cylinders. Engine would miss, water would show up on s/plugs, etc.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"
 
After all that.....It was a ba

After all that.....It was a badly and completely plugged weep hole. I said I was a "Novice"....! Thank you all so very much!!
 
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