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1983 Mercury 150 Overheating

J

John Rabalais

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" Hello Guys, I am new to the

" Hello Guys, I am new to the board. My question is I have a 1983 Mercury 150 V6. The motor runs hot at full throttle. I replaced the Water Pump, thermostats, and the pressure valve. The timing is correct, but the water pressure is between 12-15 at full throttle. The Carbs have been cleaned and checked. The problem is still there. Any Ideas? "
 
" HOW HIGH UP ON THE TRANSOM I

" HOW HIGH UP ON THE TRANSOM IS YOUR ENGINE MOUNTED? WHATS WATER PRESSURE LOOK LIKE AT OTHER RANGES BESIDES WOT? IF THE ENGINE IS MOUNTED OR JACKED TO HIGH ON A JACKPLATE , THAN YOU WONT GET ENOUGH WATER IN THE PICKUPS TO COOL IT.YOU MIGHT WANT TO MAKE SURE THAT THERE IS NOT SOME KIND OF TRASH IN THE TUBE FROM PUMP TO POWER HEAD OR THAT YOU DONT HAVE AN INTERNAL LEAK. CHECK PLUGS IF THEY ARE REAL CLEAN, MIGHT BE GETTIG WATER IN A CYLINDER. HOPE THIS HELPS. MIKE "
 
Motor is not on a jack plate.

Motor is not on a jack plate. Head Gaskets were changed and no water was found in cylinders. All areas are clean including between the block and lower unit. All new gaskets were installed. Water pressure fluctuates between 5 to 10 at idle and 10 to 15 on the way to WOT.

Help Please!!!
Thanks
 
" John, You are mixing your fu

" John, You are mixing your fuel-oil to correct mix. Were jets in carb's in anyway changed . Maybe lean at high speed "
 
I changed the Jets from .064

I changed the Jets from .064 t0 .066. This helped a little. My Tach was set up incorrectly. It was fast. I reset the tach and found out that I was only getting 4200 rpm at wot. I changed the prop from 21 to 17 pitch. Problem solved. I would like to say thanks to everyone who helped.
 
" John,

It sounds like the

" John,

It sounds like the pressure relief valve is not working properly. Remove it and see if the engine cools at full throttle.

Tony "
 
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