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Top dead center procedure.

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Bama91

Member
Would someone please explain the best method for finding top dead center on a 1993 Evinrude Ocean Pro 200 hp. I have tried the procedure from the seloc manual, but the 3rd mark is nowhere near the TDC mark cast on the flywheel.

Many thanks!
 
If I were you, I would just try to verify the setting as it is NOW.

First off, remember that when the flywheel shows ATDC, the piston is going DOWN in the cylinder, until it hits BDC. (Bottom Dead Center).
At that point, it starts to go UP in the cylinder, and is in the BTDC portion of it's rotation.

To do that, remove spark plugs. Turn engine clockwise manually til the pointer is on flywheel mark 18* ATDC. Do not allow engine to rotate.
Install piston TDC tool in cylinder #1, and adjust as necessary until it just barely touches the top of the piston.
Now, rotate clockwise manually, slowly, and the piston will travel down in the cylinder, reach BDC, and then begin to travel up in the cylinder.
Eventually the piston will hit (touch) the TDC tool "from the other side" so to speak, and that point should be at exactly 18* BTDC.

If your pointer is already adjusted right, the stopping place when piston is going UP as it approaches TDC will be 18* BTDC.

You understand? If it is, you need not adjust anything. And you will never need to adjust it again for the life of the motor. It is a one time and set adjustment.

If it is off by two degrees, for example, you only move the pointer 1 degree to adjust.
I will leave it to you to figure out which way to move it if you have to move it. Just use a little logical thinking.

The 18* starting point I mention is purely arbitrary. You could easily use 12*....whatever is more conveniently marked on the flywheel both before TDC and after TDC.
If for example, you start at 18* ATDC, and your piston stop tool will not adjust to even touch the piston, then you might have to go to 10* ATDC as starting point.

DO NOT TOUCH THE KEY FOR ANY REASON. I did so once, and when the starter rotated the piston one revolution, the piston stop tool punched a hole in the top of my piston. Still have the piston if you want to see pics.
 
It is called a piston stop tool be sure and disconnect the battery before installing the piston stop. Screw it down until it touches the piston and lock it in place then rotate the flywheel its easier with all the plugs removed just rotate clockwise until it touches the stop and make another mark on the flywheel True tdc is half the way between the two marks. You can use any point on the engine for easy reference put the flywheel on the half way mark and check the timing marks should be exactly TDC.
 
Remove "all" spark plugs.

Pick up a spark plug, even a junk s/plug that is too long for the engine, long enough to hit the piston, and screw it in #1 cylinder.

Turn the flywheel clockwise until #1 piston hits that s/plug. Mark the flywheel at the pointer.

Turn the flywheel counter clockwise until #1 piston hits that s/plug. Mark the flywheel at the pointer.

The halfway point between those two marks is TDC.

Use common sense to decide/figure "which" halfway point!
 
kimcrwbr1 said:
It is called a piston stop tool be sure and disconnect the battery before installing the piston stop. Screw it down until it touches the piston and lock it in place then rotate the flywheel its easier with all the plugs removed just rotate clockwise until it touches the stop and make another mark on the flywheel True tdc is half the way between the two marks. You can use any point on the engine for easy reference put the flywheel on the half way mark and check the timing marks should be exactly TDC.
Click to expand...

Thank y'all very much for the information. I will work on this tomorrow and post the outcome.
 
daselbee said:
If I were you, I would just try to verify the setting as it is NOW.

First off, remember that when the flywheel shows ATDC, the piston is going DOWN in the cylinder, until it hits BDC. (Bottom Dead Center).
At that point, it starts to go UP in the cylinder, and is in the BTDC portion of it's rotation.

To do that, remove spark plugs. Turn engine clockwise manually til the pointer is on flywheel mark 18* ATDC. Do not allow engine to rotate.
Install piston TDC tool in cylinder #1, and adjust as necessary until it just barely touches the top of the piston.
Now, rotate clockwise manually, slowly, and the piston will travel down in the cylinder, reach BDC, and then begin to travel up in the cylinder.
Eventually the piston will hit (touch) the TDC tool "from the other side" so to speak, and that point should be at exactly 18* BTDC.

If your pointer is already adjusted right, the stopping place when piston is going UP as it approaches TDC will be 18* BTDC.

You understand? If it is, you need not adjust anything. And you will never need to adjust it again for the life of the motor. It is a one time and set adjustment.

If it is off by two degrees, for example, you only move the pointer 1 degree to adjust.
I will leave it to you to figure out which way to move it if you have to move it. Just use a little logical thinking.

The 18* starting point I mention is purely arbitrary. You could easily use 12*....whatever is more conveniently marked on the flywheel both before TDC and after TDC.
If for example, you start at 18* ATDC, and your piston stop tool will not adjust to even touch the piston, then you might have to go to 10* ATDC as starting point.

DO NOT TOUCH THE KEY FOR ANY REASON. I did so once, and when the starter rotated the piston one revolution, the piston stop tool punched a hole in the top of my piston. Still have the piston if you want to see pics.
Click to expand...

Thank you.
Just to verify, the #1 piston is on the top left when looking at the back of the engine.

Thanks.
 
Bama91 said:
Thank you. Just to verify, the #1 piston is on the top left when looking at the back of the engine. Thanks.
Click to expand...

No, standing in back of the engine, facing the spark plugs, the cylinders are marked as follows below..... Observe the engine itself and you will see which spark plug is the highest which is always #1 cylinder.

2....1
4....3
6....5
 
joereeves said:
Remove "all" spark plugs.

Pick up a spark plug, even a junk s/plug that is too long for the engine, long enough to hit the piston, and screw it in #1 cylinder.

Turn the flywheel clockwise until #1 piston hits that s/plug. Mark the flywheel at the pointer.

Turn the flywheel counter clockwise until #1 piston hits that s/plug. Mark the flywheel at the pointer.

The halfway point between those two marks is TDC.

Use common sense to decide/figure "which" halfway point!
Click to expand...

what if the halfway point does not fall in the area of the cast degree marks on the flywheel?
 
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