Quote:
Originally Posted by Montauk17
Mercury's mexican electronics are known for giving problems as well. Makes sure everything is firing properly before you start running it again after you rebuild it. Some people don't agree with gutting the thermostat but IMO you don't need one in south LA on a carb 2 stroke. Gut the thermostat and let it flow. If you plan on doing the rebuild yourself get a mercury service manual and makes sure everything is within specs.
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It's difficult for most folks to understand the purpose of the thermostat in an outboard. It is not to make the engine run cool, it is to insure the engine block runs at the optimum temperature for performance and parts expansion. It is actually to make an engine run warmer than it would without a thermostat. Mercury is notorious for galling pistons when folks do not allow the engine block and pistons to warm properly. Most Mercury outboards use forged pistons. Forged pistons have a greater expansion rate from a cool state to their heated state than cast pistons. This means that when you first start that Mercury in cool weather, the piston is much smaller than the cylinder bore. By allowing the engine to warm before takeoff, you allow the pistons to grow and properly fit the bore. If you just start the engine and blast off, piston slap will eventually cause the piston to gall aluminum and stick it to the cylinder wall.
As for the port job, there is more science to it than just grinding 1 port. If it were that simple, everyone would be QUALIFIED engine builders. There are several excellent engine builders in this area. Each usually specializes in one or two brands of motor and only certain sizes of those motors. It is a time consuming task to map out the ports and enter all the data into a good port mapping program and come up with the correct sizes to make ALL ports in that cylinder, intake, transfer, and exhaust ports work together PROPERLY! To modify one port in each cylinder is like putting a 20" wheel on one corner of your vehicle and 15" wheels on the other 3, it will roll, just not correctly. All ports must be properly and proportionately sized to work together.
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