[Blu_Lunch]

After starting the thread about T-stats, there was talk about running/not running T-stats I ran across this it make a ton of sense.


1) A outboard motor does not warm up very fast if at all at an idle in cold water.
2)Thermostats can only help it warm up so fast if you have 40 +/- deg. water running through your power head.
So how do you run a Opti or other outboard under these conditions?
1) Idle at least 3-4 minutes minimum.
2) Take off easy.....Do NOT hammer down from an idle while still cold. Take it easy for a ways. Increase the RPM's gradual.
3) Make sure your thermostats are working properly!
* This one is very important ... (I had this happen to me) I was running a 2004 225 Opti in 40 deg. water, motor was running at 130 deg range it picked up a pebble and stuck it in a thermostat (held it open) I had Smart Craft gauges and always have it on eng. temp in cold weather/water..
When the thermostat got stuck open it cooled the motor down to less than 80 degrees!...It would NOT go above 80 degrees even at WOT!
So what's the problem??
First you have a certain amount of clearance between the piston and cylinder wall.
example... cyl bore on a 200/225 Opti is 3.6265 in. (std.) The piston has approx. dia. of 3.6210... So you have approx. .0055 piston to cylinder wall clearance...
Now when a motor heats up it expands...So when it's up to normal operating temp. the piston and cylinder wall are both a larger diameter.
When you run a cold motor hard or up to WOT real quick what happens is the piston gets hot much faster than a cylinder wall that has cold water against the outside of it....The hot piston expands but the cylinder wall hasn't yet....What happens from there is called a Cold Seize.. The expanded piston don't have the .0055 clearance needed and it will seize or stick to the cylinder wall. If it seizes/sticks running @ 5500 RPM + it just rips the wrist pin/connecting rod right out of the piston...The connecting rod will go out of control and end up out through the side of the block...At this point the power head is destroyed...This is one of biggest failure issue of a Optimax and one that can be avoided by just following the above info. by making sure it warms up and has time to warm up right ........