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8v71 overheat problem

T

Travis Handy

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"I have a 2 stroke DD 8v71 in

"I have a 2 stroke DD 8v71 in a commercial fishing boat. My water pump went out on me and i had a mechanic replace it($2,600. before he replaced it I think my brother overheated the engine. Now the engine can be run all day @ 1800rpm's , but if I go over 1950 to 2000rpms it overheats in about 1-3 minutes. I havent checked the thermostats- they are brand new. There is no coolant in my oil. This boat has a heat exchanger and is keel cooled. I was told I should flush the cooling system, change thermostats, or i might have a air lock in the cooling system? I keep hearing from mechanics that I have a blown head gasket(they haven't looked at it) how much do you have to heat this thing up to blow a head gasket? I got a quote for over $5,000 to change the head gaskets and have a opertunity to buy a RTO for 2,000. I'm thinking I might buy the other engine and exchange it if thats my cheapest option. Does anyone have an easy fix for this overheat problem?"
 
"WILL IT DONT SOUND LIKE A HEA

"WILL IT DONT SOUND LIKE A HEAD GSK PROBLEM OR YOU WHOULD BE BLOWING WATER OUT OF HEAT EXCHANGER SYETEM.SOUNDS LIKE AIR LOCK IN SYSTEM, CLEAN SYSTEM AND PURG AND TRY."
 
"The problem started with the

"The problem started with the water pump leaking coolant, then after the mechanic replaced the water pump the engine started overheating. how would you recomend purging the system?"
 
"THERE SHOULD VALVES WERE THE

"THERE SHOULD VALVES WERE THE KEEL COOLER PIPES GO THR THE HAUL AND WERE THEY COME BACK AT, AND ALSO THERE IS A BLEED VALVE AT THE BACK END OF THE COOLER. WHAT YOU MIT IS FIND BLEED VALVE, START ENGINE AND OPEN VALVE AND LET RUN AND SEE IF AIR COME OUT AND THEN AT THR HUAL AND THEN ON ENGINE BEFOR STATS. NOTE DO NOT SHUT ENGINE OFF WITH ENY VALVES OPEN."
 
I was told by an old DD mechan

I was told by an old DD mechanic that the mechanic probebly smeared RTV over the air relief hole in the thermostat when he changed it possibly causing the air lock. Is this a likely senerio? He also said that if their is no oil in the heat exchanger or coolant in the oil and no bubbles present when I look in the heat exchanger that the thermostat is the next place to look. I am hopeing to get away with just changing a thermostat and not a head.
 
Re: "I have a 2 stroke DD 8v71 in

"I have a 2 stroke DD 8v71 in a commercial fishing boat. My water pump went out on me and i had a mechanic replace it($2,600. before he replaced it I think my brother overheated the engine. Now the engine can be run all day @ 1800rpm's , but if I go over 1950 to 2000rpms it overheats in about 1-3 minutes. I havent checked the thermostats- they are brand new. There is no coolant in my oil. This boat has a heat exchanger and is keel cooled. I was told I should flush the cooling system, change thermostats, or i might have a air lock in the cooling system? I keep hearing from mechanics that I have a blown head gasket(they haven't looked at it) how much do you have to heat this thing up to blow a head gasket? I got a quote for over $5,000 to change the head gaskets and have a opertunity to buy a RTO for 2,000. I'm thinking I might buy the other engine and exchange it if thats my cheapest option. Does anyone have an easy fix for this overheat problem?"
Just went through same issue. Engine driven keel cooling pump. Lock nut came loose on the impeller causing thermostat failure symptom. Lucky, never messed up the water seal. Tighten with Loc-tite and add washer to ensure the shaft threads ok. Runs mint now. To check your head gasket. Place a plastic bag with elastic over your rad cap or vent tube on your header tank if you have one. (engine warm) and test run. If bag gets bigger, head gasket, if not, check your new water pump. Not the first new part that does not work. Good luck.
 
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