Mercury 1500 150HP questions

novice boater54

Seaman Apprentice
Joined
Jul 20, 2008
Messages
42
Can someone possibly tell me where to find the thermostat (if there is one) on a 1976 Mercury 150HP outboard.
Can someone also tell me how expensive and difficult is it to replace rings and related parts on this motor. Motor has been sitting for a year or so, apparently it ran last year so we're told. I am the one who gets to work on this project because the young owner doesn't know much about mechanics or motors.
Compression is low or negligable in #1, and #3 which is 30lbs, #'s 2,4,5 are over 100ls and #6 was unreachable at this point due to removing lower shroud later but appears to have some pressure when finger is placed over the hole while cranking.
What would a preliminary diagnosis be on this motor?
The rest appeasr to be in fairly good condition except cleaing carbs. Can this be done without sacrificing carb sync settings as well?
Got a lot to learn with this baby I'm sure.
Thanks for any help.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,030
Re: Mercury 1500 150HP questions

There is no thermostat on that motor.

A new oversize piston and ring set for that motor is about $100. You need to strip the motor down to the bare block and bore out that #1 cylinder (~$50) and reasemble, using new gaskets. Normally this is a $1000 job at a shop.

Now you need to find out what the problem that ruined the cylinder and fix it, or it will happen again. Likely culprits are dirty carbs, bad cooling or overadvanced timing. unless you can do the work yourself, you might consider another motor.
 
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