Demolitron
Seaman Apprentice
- Joined
- Sep 17, 2007
- Messages
- 32
Mercruiser Serial #A396855
So I may be doing a reseal on a Mercruiser MR 205, I wanted to verify I am reading the manual & diagrams correctly. I am currently redoing the Driveshaft Housing yolk seal and U-Joints. I was going to pressure test the thing and see if it would hold but I also want to tear it down to look inspect the bearings. So, since I'm in there and resealing kits seem to be cheap, I thought I would do it. If anyone would weigh in on how hard a resealing job is it would help me make a decision.
This is a brain dump of how I understand the sealing systems to work on a Mercruiser MR 205. I know this post is long, but perhaps it can also help others to understand all of the sealing systems on these drives.
I may seem to make statements, but everything here is a question. If I am wrong please let me know,
Oil Seal operating assumptions:
?Oil seals are essentially unidirectional. The side of the seal that that lip is facing is designed to have a positive pressure differential referenced to the side the seal lip is not facing. With a positive pressure on the lip face it will expand the rubber bellows causing an increase in sealing pressure against the rotating shaft. Pressure on the opposite side does not expand the bellows, causing little or negative sealing pressure on the rotating shaft.
The presence of the spring on the inner face facilitates the initial weak seal and also provide some negative pressure sealing power.
Gear Housing
Essentially, there are four sealing areas to be concerned with
?Drive Shaft ? O-Ring #23 creates a static seal between the gear housing #1 and the Base Assembly #24. Oil Seals #25 & 26 create a dynamic seal between the base assembly and the drive shaft #14. Seal #26 is installed with the lip facing the wet side so it keeps water out. Seal #25 is installed with the lip facing the oil side so it keep oil in.
Question, Gasket #22, is this a critical sealing area or does it just help out O-Ring #23? It must also help guard against pressure/volume leakage of the water circulation system. If it leaks I don?t see water getting into the oil or vice versa.
?Shift Shaft ? Seal #48 is pressed into bushing #47 and forms the main moving seal. O-Ring #46 seals the bushing to the gear housing. I see it says the bushing and seal are replaced as one. Can anyone say why? Also, is washer #45 a mechanical support or does it contribute to the seal?
?Propeller Shaft Bearing Carrier ? O-Ring #21 Seals the bearing carrier #23 against the Gear Housing #2 to stop water/oil. Seals #26 & 25 serve as the moving sealing component from the shaft to the bearing carrier and are installed back to back to form a double lip seal keeping water out and oil in.
?Gear Housing Oil Seal ? Small O-Ring #5 seals the passage that allows oil to flow up from the Gear Case to the Drive Shaft Housing.
Drive Shaft Housing
Here there are three locations that are important for sealing
?Input Shaft & Yolk ? Here Seal #29 presses into seal carrier #30 for the dynamic seal on the input shaft yolk. Seal is installed with lip facing the oil side, so it will primarily keep oil in and less effectively or fail to keep water out. O-Ring #31 forms a static seal of the seal carrier to the drive shaft housing. This sealing system is designed to primarily keep gear oil inside, as there is only one seal and it is installed with the seal lip facing inwards.
?Top Cover ? Here O-Ring #4 forms a static seal.
?Driven Gear Seal ? Here Seals #13 & 14 are pressed into the drive shaft housing and without a seal carrier there is no need for any O-Rings. These form the dynamic seal around the driven gear shaft. This is a double seal and I am confused about the seal direction. It looks like the manual states that both seals should be driven with their lips facing up towards the top of the housing. Putting the emphasis on keeping oil in, rather than water out. Is this correct?
I think it would be that seal #14 would be installed with the seal lip facing towards the wet side to keep water out. And seal #13 would be installed with the seal lip facing the oil side to keep oil in. Reversed and there may be oil mixing in between the two seals.
?What about the water pocket cover gasket #41? Is this a critical seal, or is it there to keep water leakage at a minimum? From what I can see in the drawings, its failure won?t result in water intrusion into the gear oil.
?Regarding the shift-shaft here in the driveshaft housing, there isn?t any penetration into the gear lube cavity, so the bushings here are strictly for mechanical support, correct?
?Also what is the splash plate and associated gasket and O-Ring?
Transom Assembly
Here I am using a exploded parts drawing I got from Crowley marine.
?Shift Assembly ? (Gimbal Housing Drawing) Here I see that the shift bellows #22 is sealed to the Transom Assembly using a Hose Clamp #24. The shift cable is threaded through the bellows and is sealed with clamp #23. This prevents water from entering the boat.
The threaded end of the shift cable screws into the bell housing and there forms a seal against water intrusion into the bell housing.
Now, water is prevented from entering the shift cavity in the bell housing by the main sealing gasket #2 (Bell Housing Drawing). This seems like it has a very thin gasket section on the starboard side of the bell housing, does this often leak? If it did it would let water into the shift cavity.
The upper shift shaft passes through the bell housing via the upper shift shaft bushing, my serial # drive does not have the integrated bushing/seal so I also have a seal above the bushing. Do I replace my upper shift shaft bushing with the integrated Mercruiser Part # 23-505041A2?
These parts should seal out any water regarding the shift systems in the transom assembly, correct?
? The exhaust bellows and system are wet, so no considerations need to be made, correct?
? U-Joint Bellows ? (Bell Housing Drawing) Bellows #14 seal against the transom assembly using clamp #16 and likewise to the bell housing. Inside the bell housing there is a large O-Ring #8, what does this do? I think it is a backup for the gasket #2, in case water gets in this O-Ring will seal around the driveshaft housing pilot keeping water out of the bellows. Can anyone confirm this?
? Coolant Water ? Here O-Ring #9 seals the water passage from the driveshaft housing to the bell housing cavity. Also a water hose and clamps seal on the bell housing and likewise to the transom assembly.
? Trim Sender Wires ? I am at a loss to see where the sending wires penetrate the transom assembly. Are there any rubber sealing components involved that need to be replaced to prevent water intrusion into the boat or outdrive?
? Gimbal Housing ? (Gimbal Housing Drawing) Gasket #31 seals the Gimbal Housing against the transom of the boat. Do these go bad often and need replaced? How can I determine if it is leaking?
Wow, that was long, but I hope complete.
Thanks everyone for reading through this thing.
So I may be doing a reseal on a Mercruiser MR 205, I wanted to verify I am reading the manual & diagrams correctly. I am currently redoing the Driveshaft Housing yolk seal and U-Joints. I was going to pressure test the thing and see if it would hold but I also want to tear it down to look inspect the bearings. So, since I'm in there and resealing kits seem to be cheap, I thought I would do it. If anyone would weigh in on how hard a resealing job is it would help me make a decision.
This is a brain dump of how I understand the sealing systems to work on a Mercruiser MR 205. I know this post is long, but perhaps it can also help others to understand all of the sealing systems on these drives.
I may seem to make statements, but everything here is a question. If I am wrong please let me know,
Oil Seal operating assumptions:
?Oil seals are essentially unidirectional. The side of the seal that that lip is facing is designed to have a positive pressure differential referenced to the side the seal lip is not facing. With a positive pressure on the lip face it will expand the rubber bellows causing an increase in sealing pressure against the rotating shaft. Pressure on the opposite side does not expand the bellows, causing little or negative sealing pressure on the rotating shaft.
The presence of the spring on the inner face facilitates the initial weak seal and also provide some negative pressure sealing power.
Gear Housing
Essentially, there are four sealing areas to be concerned with
?Drive Shaft ? O-Ring #23 creates a static seal between the gear housing #1 and the Base Assembly #24. Oil Seals #25 & 26 create a dynamic seal between the base assembly and the drive shaft #14. Seal #26 is installed with the lip facing the wet side so it keeps water out. Seal #25 is installed with the lip facing the oil side so it keep oil in.
Question, Gasket #22, is this a critical sealing area or does it just help out O-Ring #23? It must also help guard against pressure/volume leakage of the water circulation system. If it leaks I don?t see water getting into the oil or vice versa.
?Shift Shaft ? Seal #48 is pressed into bushing #47 and forms the main moving seal. O-Ring #46 seals the bushing to the gear housing. I see it says the bushing and seal are replaced as one. Can anyone say why? Also, is washer #45 a mechanical support or does it contribute to the seal?
?Propeller Shaft Bearing Carrier ? O-Ring #21 Seals the bearing carrier #23 against the Gear Housing #2 to stop water/oil. Seals #26 & 25 serve as the moving sealing component from the shaft to the bearing carrier and are installed back to back to form a double lip seal keeping water out and oil in.
?Gear Housing Oil Seal ? Small O-Ring #5 seals the passage that allows oil to flow up from the Gear Case to the Drive Shaft Housing.
Drive Shaft Housing
Here there are three locations that are important for sealing
?Input Shaft & Yolk ? Here Seal #29 presses into seal carrier #30 for the dynamic seal on the input shaft yolk. Seal is installed with lip facing the oil side, so it will primarily keep oil in and less effectively or fail to keep water out. O-Ring #31 forms a static seal of the seal carrier to the drive shaft housing. This sealing system is designed to primarily keep gear oil inside, as there is only one seal and it is installed with the seal lip facing inwards.
?Top Cover ? Here O-Ring #4 forms a static seal.
?Driven Gear Seal ? Here Seals #13 & 14 are pressed into the drive shaft housing and without a seal carrier there is no need for any O-Rings. These form the dynamic seal around the driven gear shaft. This is a double seal and I am confused about the seal direction. It looks like the manual states that both seals should be driven with their lips facing up towards the top of the housing. Putting the emphasis on keeping oil in, rather than water out. Is this correct?
I think it would be that seal #14 would be installed with the seal lip facing towards the wet side to keep water out. And seal #13 would be installed with the seal lip facing the oil side to keep oil in. Reversed and there may be oil mixing in between the two seals.
?What about the water pocket cover gasket #41? Is this a critical seal, or is it there to keep water leakage at a minimum? From what I can see in the drawings, its failure won?t result in water intrusion into the gear oil.
?Regarding the shift-shaft here in the driveshaft housing, there isn?t any penetration into the gear lube cavity, so the bushings here are strictly for mechanical support, correct?
?Also what is the splash plate and associated gasket and O-Ring?
Transom Assembly
Here I am using a exploded parts drawing I got from Crowley marine.
?Shift Assembly ? (Gimbal Housing Drawing) Here I see that the shift bellows #22 is sealed to the Transom Assembly using a Hose Clamp #24. The shift cable is threaded through the bellows and is sealed with clamp #23. This prevents water from entering the boat.
The threaded end of the shift cable screws into the bell housing and there forms a seal against water intrusion into the bell housing.
Now, water is prevented from entering the shift cavity in the bell housing by the main sealing gasket #2 (Bell Housing Drawing). This seems like it has a very thin gasket section on the starboard side of the bell housing, does this often leak? If it did it would let water into the shift cavity.
The upper shift shaft passes through the bell housing via the upper shift shaft bushing, my serial # drive does not have the integrated bushing/seal so I also have a seal above the bushing. Do I replace my upper shift shaft bushing with the integrated Mercruiser Part # 23-505041A2?
These parts should seal out any water regarding the shift systems in the transom assembly, correct?
? The exhaust bellows and system are wet, so no considerations need to be made, correct?
? U-Joint Bellows ? (Bell Housing Drawing) Bellows #14 seal against the transom assembly using clamp #16 and likewise to the bell housing. Inside the bell housing there is a large O-Ring #8, what does this do? I think it is a backup for the gasket #2, in case water gets in this O-Ring will seal around the driveshaft housing pilot keeping water out of the bellows. Can anyone confirm this?
? Coolant Water ? Here O-Ring #9 seals the water passage from the driveshaft housing to the bell housing cavity. Also a water hose and clamps seal on the bell housing and likewise to the transom assembly.
? Trim Sender Wires ? I am at a loss to see where the sending wires penetrate the transom assembly. Are there any rubber sealing components involved that need to be replaced to prevent water intrusion into the boat or outdrive?
? Gimbal Housing ? (Gimbal Housing Drawing) Gasket #31 seals the Gimbal Housing against the transom of the boat. Do these go bad often and need replaced? How can I determine if it is leaking?
Wow, that was long, but I hope complete.
Thanks everyone for reading through this thing.
