3.7L rear main seal question
 

Hi,

I have a 1986 3.7L inline 4 cyl by Mercruiser. Just had all 3 bellows
and drive yoke replaced and now it appears I need a new rear main seal
on the motor (I know these aren't related repairs). It's leaking oil
out the back above the oil pan. Has anyone done or had this repair
done to theirs? I've worked on a few car motors and have friends with
extensive car motor rebuilding experience, and thought of possibly
tackling the job myself. Is the rear main seal a two piece or 1 pc on
the 3.7 Merc motor? Can the seal be replaced without motor removal?
If you paid to have this done, can you give me a ball park figure on
price, and other common repairs done with the seal?
Someone mentioned a "ready sleeve" to repair crank shaft sealing
surfaces.

Thanks
Ted

3.7L rear main seal question
 

1) Two piece seal.

2) Can't be replaced without removing motor.

3) A "Redi-sleeve" is used to provide a new sealing surface on a scored
shaft. It cannot be used for a rear main problem since it is one piece
and won't pass by the flywheel mounting flange.
Ted wrote:

Hi,

I have a 1986 3.7L inline 4 cyl by Mercruiser. Just had all 3 bellows
and drive yoke replaced and now it appears I need a new rear main seal
on the motor (I know these aren't related repairs). It's leaking oil
out the back above the oil pan. Has anyone done or had this repair
done to theirs? I've worked on a few car motors and have friends with
extensive car motor rebuilding experience, and thought of possibly
tackling the job myself. Is the rear main seal a two piece or 1 pc on
the 3.7 Merc motor? Can the seal be replaced without motor removal?
If you paid to have this done, can you give me a ball park figure on
price, and other common repairs done with the seal?
Someone mentioned a "ready sleeve" to repair crank shaft sealing
surfaces.

Thanks
Ted

3.7L rear main seal question
 

Thanks for the info Jim.

I only wish the Merc dealer, that just did the bellows 1 week
before, had mentioned the problem then. From reading my manual, the
outdrive must be removed before re-installing the engine, to line up
the spline shaft to pto, if they do have to replace the rear main
seal. The motor is 17 years old, but the rear main leak happened very
suddenly, possibly indicating a bent crank. I know the T.I.R. for the
crank is .001", but can this be measured with the motor in the boat?
Since the bellow were just done 1 week ago, can they be pulled free,
then reglued and clamped without damaging them?

Thanks again for any help,
Ted


Jim Kelly wrote in message ...
1) Two piece seal.

2) Can't be replaced without removing motor.

3) A "Redi-sleeve" is used to provide a new sealing surface on a scored
shaft. It cannot be used for a rear main problem since it is one piece
and won't pass by the flywheel mounting flange.
Ted wrote:

Hi,

I have a 1986 3.7L inline 4 cyl by Mercruiser. Just had all 3 bellows
and drive yoke replaced and now it appears I need a new rear main seal
on the motor (I know these aren't related repairs). It's leaking oil
out the back above the oil pan. Has anyone done or had this repair
done to theirs? I've worked on a few car motors and have friends with
extensive car motor rebuilding experience, and thought of possibly
tackling the job myself. Is the rear main seal a two piece or 1 pc on
the 3.7 Merc motor? Can the seal be replaced without motor removal?
If you paid to have this done, can you give me a ball park figure on
price, and other common repairs done with the seal?
Someone mentioned a "ready sleeve" to repair crank shaft sealing
surfaces.

Thanks
Ted

3.7L rear main seal question
 

Ted,
It would be very unusual for the crank to be bent enough in the area of the rear main
to cause a leak.
I do not believe that there is any way to get in there to take a run out measurement
without removing the engine from the boat. Are you sure that the problem is the rear
main seal? Have you checked the valve cover gasket and oil pan gasket for possible
leakage? Oil collects at the back of the valve cover and, if the gasket leaks,
sometimes seeps down and drips off the bottom of the engine below the rear main seal.

If it is in fact a rear main leak, you will have to remove the drive and pull the
engine. Since the bellows were just replaced, you should have no trouble removing
them and re-using. When re-installing the engine, the alignment should be checked by
inserting an alignment tool through the gimbal bearing into the engine coupler.
When replacing the rear main seal, the easiest way is to put the engine on a stand
and turn it upside down. Remove the oil pan and the rear bearing cap. Loosen the
other main bearing cap bolts so that the crank can be raised slightly at the rear.
Snake the top half of the seal out of the block and slide the new one in. The bottom
half is installed in the rear cap and the cap is installed. Torque all of the bolts
to specification and re-install the oil pan with a new gasket. Since this engine is
unique in that it has an alternator rotor directly mounted on the crank nose, be
careful to raise the crank only the minimum to just work the top half of the seal
out.

Ted wrote:

Thanks for the info Jim.

I only wish the Merc dealer, that just did the bellows 1 week
before, had mentioned the problem then. From reading my manual, the
outdrive must be removed before re-installing the engine, to line up
the spline shaft to pto, if they do have to replace the rear main
seal. The motor is 17 years old, but the rear main leak happened very
suddenly, possibly indicating a bent crank. I know the T.I.R. for the
crank is .001", but can this be measured with the motor in the boat?
Since the bellow were just done 1 week ago, can they be pulled free,
then reglued and clamped without damaging them?

Thanks again for any help,
Ted

Jim Kelly wrote in message ...
1) Two piece seal.

2) Can't be replaced without removing motor.

3) A "Redi-sleeve" is used to provide a new sealing surface on a scored
shaft. It cannot be used for a rear main problem since it is one piece
and won't pass by the flywheel mounting flange.
Ted wrote:

Hi,

I have a 1986 3.7L inline 4 cyl by Mercruiser. Just had all 3 bellows
and drive yoke replaced and now it appears I need a new rear main seal
on the motor (I know these aren't related repairs). It's leaking oil
out the back above the oil pan. Has anyone done or had this repair
done to theirs? I've worked on a few car motors and have friends with
extensive car motor rebuilding experience, and thought of possibly
tackling the job myself. Is the rear main seal a two piece or 1 pc on
the 3.7 Merc motor? Can the seal be replaced without motor removal?
If you paid to have this done, can you give me a ball park figure on
price, and other common repairs done with the seal?
Someone mentioned a "ready sleeve" to repair crank shaft sealing
surfaces.

Thanks
Ted

3.7L rear main seal question
 

Thanks again Jim. I had the repair done by mechanic. As suggested,
the crank T.I.R. was fine but the rear main seal needed replaced. He
did have to remove the out-drive as there wasn't enough room in front
of motor to pull it forward enough to clear the spline coupler.
Removing the drive didn't affect the bellows. He also replaced front
main seal and cam shaft driven water pump seals. Cam shaft was
somewhat scored so he didn't press them in as far, so the ride in a
different area of the cam shaft. New oil pan gasket while he was in
there. Valve cover gasket was ok. So far no coolant loss or oil
leaks. Haven't got a exact total other than 9 hrs x $50 labor + parts

Ted
Jim Kelly wrote in message ...
Ted,
It would be very unusual for the crank to be bent enough in the area of the rear main
to cause a leak.
I do not believe that there is any way to get in there to take a run out measurement
without removing the engine from the boat. Are you sure that the problem is the rear
main seal? Have you checked the valve cover gasket and oil pan gasket for possible
leakage? Oil collects at the back of the valve cover and, if the gasket leaks,
sometimes seeps down and drips off the bottom of the engine below the rear main seal.

If it is in fact a rear main leak, you will have to remove the drive and pull the
engine. Since the bellows were just replaced, you should have no trouble removing
them and re-using. When re-installing the engine, the alignment should be checked by
inserting an alignment tool through the gimbal bearing into the engine coupler.
When replacing the rear main seal, the easiest way is to put the engine on a stand
and turn it upside down. Remove the oil pan and the rear bearing cap. Loosen the
other main bearing cap bolts so that the crank can be raised slightly at the rear.
Snake the top half of the seal out of the block and slide the new one in. The bottom
half is installed in the rear cap and the cap is installed. Torque all of the bolts
to specification and re-install the oil pan with a new gasket. Since this engine is
unique in that it has an alternator rotor directly mounted on the crank nose, be
careful to raise the crank only the minimum to just work the top half of the seal
out.

Ted wrote:

Thanks for the info Jim.

I only wish the Merc dealer, that just did the bellows 1 week
before, had mentioned the problem then. From reading my manual, the
outdrive must be removed before re-installing the engine, to line up
the spline shaft to pto, if they do have to replace the rear main
seal. The motor is 17 years old, but the rear main leak happened very
suddenly, possibly indicating a bent crank. I know the T.I.R. for the
crank is .001", but can this be measured with the motor in the boat?
Since the bellow were just done 1 week ago, can they be pulled free,
then reglued and clamped without damaging them?

Thanks again for any help,
Ted

Jim Kelly wrote in message ...
1) Two piece seal.

2) Can't be replaced without removing motor.

3) A "Redi-sleeve" is used to provide a new sealing surface on a scored
shaft. It cannot be used for a rear main problem since it is one piece
and won't pass by the flywheel mounting flange.
Ted wrote:

Hi,

I have a 1986 3.7L inline 4 cyl by Mercruiser. Just had all 3 bellows
and drive yoke replaced and now it appears I need a new rear main seal
on the motor (I know these aren't related repairs). It's leaking oil
out the back above the oil pan. Has anyone done or had this repair
done to theirs? I've worked on a few car motors and have friends with
extensive car motor rebuilding experience, and thought of possibly
tackling the job myself. Is the rear main seal a two piece or 1 pc on
the 3.7 Merc motor? Can the seal be replaced without motor removal?
If you paid to have this done, can you give me a ball park figure on
price, and other common repairs done with the seal?
Someone mentioned a "ready sleeve" to repair crank shaft sealing
surfaces.

Thanks
Ted