Mercruiser Bravo Sterndrive Service and Maintenance

All of the boats I have owned since 2003 have had Mercruiser Bravo III sterndrives. I try to do my best to maintain them, and before creating this page I couldn't always remember all of the individual maintenance steps that needed to be done. Occassionally, I ended up making repairs that could have been prevented by recommended maintenance. So finally I decided to put this information on my website, where I could easily reference it from anywhere. I could also share it with anyone else who might find it useful, and invite comments to maybe fine tune the steps or add new steps that I hadn't thought about. This should give us all a great reference for what needs to be done to keep our sterndrives in great shape.

I started out by obtaining the Mercruiser Bravo Service Manual, also called Service Manual #28. The copy I used to develop this page was dated June 2003. I don't really expect anything covered here has changed, but if anyone can provide a newer service manual, or advise me of any changes, I would definitely welcome that. Also, since this manual covers all Bravo sterndrives, everything presented here also pertains to Bravo I and Bravo II sterndrives. This is all just routine maintenance, nothing that would be involved enough that the internal differences of these drives would come into play.

The sections of Service Manual #28 that I referred to are listed below, and each is linked to a PDF file of that section in case you would like to download it and review it:

Table of Contents / Notice to Users
Section 1B - Maintenance
Section 2A - Removal, Installation and Adjustment
Section 4A - Transom Assembly Service Procedures Requiring Minor Disassembly
Section 7A - Corrosion Protection

I'm not going to break the steps down into winterizing (layup) / de-winterizing (recommissioning) like they do in the service manual, but instead I'm going to list everything in the order I would do it, since I generally do all of this in the spring. It's too cold when I put the boat away for the winter to mess with this stuff. This first section deals with stuff that needs to be done from the inside of the boat. It can be done with the sterndrive on or off of the boat, but I think it's better to have the drive drained of gear oil and removed from the boat first. If nothing else, at least begin draining the gear oil before starting the steps inside the boat so that it will hopefully be done draining by the time you're ready for the steps outside of the boat. I know the stuff inside the boat isn't servicing the sterndrive itself, but it is servicing components that directly interact with the sterndrive, so I'm including them.

In order to keep this page from being incredibly long, I've shrunk each step down to display just the title. Click on it to show the details of that step. With all of the steps contracted, it's easy to take a look at the materials and tools needed, so that if you were planning to do all of these steps in one trip to the boat, you would be able to gather up everything you needed to bring with you.

Almost all of these steps are easier or more fun with someone to help, so try to recruit a friend for help doing this stuff!

From inside the boat:

Lubricate the Shift Cable (Click to expand)

Frequency: Annually
Materials needed: SAE 30W Engine Oil
Tools needed: None

  1. Lubricate the pivot points and the guide contact surfaces with SAE 30W Engine Oil. The picture below shows the 3 pivot points (a) and the 2 guide contact surfaces (b). I pour the oil into the cap from the oil can, and carefully pour a little bit onto all of the areas shown below, keeping a rag handy to wipe up any spillage.  Using some kind of dropper or something might be a less messy method, so let me know if you have any suggestions. This is an important step to keep your boat shifting smoothly and prolonging the life of your shift cables! (Reference: Section 1B, Page 10)
    Shift Bracket

Lubricate the Steering System (Click to expand)

Frequency: Every 100 hours or Annually
Materials needed: SAE 30W Engine Oil, Special Lubricant 101 (92-802865A1)
Tools needed: Grease Gun

  1. These three steps are done behind the engine, near the transom. This first step only applies if your steering cable has a grease fitting. Turn the steering wheel until the steering cable is fully retracted into the cable housing. Apply approximately 3 pumps of Special Lubricant 101 to the grease fitting. The picture below shows the location of the grease fitting (a). My problem here is that I have only ever been able to find Special Lubricant 101 in a tube, not in a grease gun cartridge. I'm pretty sure I read that 2-4-C with Teflon is the suitable replacement for Special Lubricant 101, and it is available in a cartridge. If anyone can confirm this for me with a reference, that would be great. In the meantime I use 2-4-C for this despite the manual calling for Special Lubricant 101. (Reference: Section 1B, Page 22)
    Steering Cable Grease Fitting
  2. Turn the steering wheel until the steering cable is fully extended from the cable housing. Lightly lubricate the exposed part of the cable with Special Lubricant 101. The picture below shows the extended steering cable (a). I squeeze Special Lubricant 101 on the cable and smear it around with my fingers. (Reference: Section 1B, Page 22)
    Steering Cable Contact Surface
  3. Lubricate the steering system pivot points with SAE 30W Engine Oil The picture below shows the pivot points where the steering arm connects to the steering cable (a). (Reference: Section 1B, Page 23)
    Steering System Pivot Points
  4. This final step only applies to twin engine boats. Lubricate the tie bar pivot points with SAE 30W Engine Oil. I don't have a picture of this, but basically it's just the same thing on the steering arm of the other drive. (Reference: Section 1B, Page 23)

Lubricate the Engine Coupler (Click to expand)

Frequency: Every 100 hours or Annually
Materials needed: Engine Coupler Spline Grease (92-802869A1)
Tools needed: Grease Gun

  1. Lubricate the engine coupler splines through the grease fitting(s) on the coupler by applying approximately 8-10 pumps of Engine Coupler Spline Grease to the grease fitting(s). The picture below shows the grease fittings (a) on steel couplers (left) and aluminum couplers (right). Even though this procedure is recommended every 100 hours, replacing a worn out coupler is enough of a pain that greasing it every 50 hours or so isn't a bad idea. Note that this procedure actually makes the most sense when the sterndrive is attached to the boat, so you may want to leave this for the very last step. (Reference: Section 1B, Page 24)
    Engine Couplers

Clean the Gear Lube Monitor (Click to expand)

Frequency: Every 2 Years
Materials needed: Rag and/or solvent, or parts washer
Tools needed: Pliers

  1. If you've drained the gear oil from the outdrive, now's a good time to take a look inside the gear lube monitor for any sludge. If you haven't drained the gear oil, well, then try again next year. If there is some sludge in there, I like to remove the reservoir by unhooking the rubber strap that holds it in, disconnecting the two bullet connectors that go to the alarm, and removing the plastic clamp that holds the hose on. The pliers might come in handy here, as they will when it's time to reconnect the hose. I then use the parts washer to run some solvent in the reservoir, slosh it around, and empty it, until it looks pretty clean. You could also use a rag and some spray solvent to get the worst out of there, but be careful not to use a solvent strong enough to damage the plastic. Also rinse it with water afterwards and allow to dry completely or dry it off with compressed air. The picture below shows the gear lube monitor (a). (Reference: Personal experience)
    Gear Lube Monitor

From outside the boat:

Remove the Sterndrive (Click to expand)

Frequency: Every 200 Hours or Annually
Materials needed: None
Tools needed: 5/8" socket, swivel, extension, and 3/8" ratchet; 5/8" combination wrench

  1. Disconnect the speedometer cable from the sterndrive. You may or may not have to do this if your speedometer is driven by a pitot or paddle wheel attached to the transom, or if you have two drives and the speedometer is connected to the other one. But you should definitely check before ignoring this step so that you don't end up having to replace some broken pieces. You will probably have to put the drive up at least part way, the higher the better. Then reach around to the side of the drive closest to the transom, turn the hose fitting about a quarter turn counter-clockwise, and pull the hose out. The picture below shows this process. (Reference: Section 2A, Page 6)
    Speedometer Hose Fitting
  2. Disconnect the trim cylinders from the sterndrive. To do this, put the drive down until the cavitation plate is level with the ground. This should be almost all the way down if not all the way. If you're using a drive cart, put the cart under the drive now, but don't tighten it up just yet. Remove the end caps (a) by turning them counter-clockwise, which you should be able to do with your hand. Next, hold the nut (b) on one side of the drive with the combination wrench, and unscrew the other nut (b) with the socket and ratchet. When one of the nuts comes off, remove the flat washer (c) and bushing (d) from that side. Then pull the anchor pin (the threaded rod the nut screws on to) out by putting the combination wrench on the remaining nut and spinning it both ways while pulling it away from the drive. Shaking the drive up and down a bit should help it come out more easily. Remember that when the anchor pin is out, nothing will be holding the drive up anymore, so it will want to fall against the transom. This is OK, just be sure to hold it and let it down gently instead of slamming against the boat. If you are using a drive cart to hold the drive, it will prevent the drive from dropping. Once the anchor pin is out, you should tighten up the drive cart.  (Reference: Section 2A, Page 6)
    Trim Cylinders
  3. Remove the locknuts that hold the sterndrive to the bell housing. Do this by using the socket, swivel, extension and ratchet to remove all 6 locknuts, (a) in the picture below. There will be 5 flat washers, remove those as well. The center nut on the port side will have a ground plate (b) under it instead of a flat washer. The ground plate does not get removed. (Reference: Section 2A, Page 7)
    Sterndrive and Bell Housing
  4. Remove the sterndrive from the boat. If you're using a drive cart, go ahead and tighten it up now. If not, have a strong friend handy for this part. Make sure the shift lever on your boat is in neutral. Pull the sterndrive away from the boat, but don't let it get more than about two inches from the bell housing.  Reach between the drive and the bell housing and make sure the shift cable linkage jaws (a) open up and release the shift cable end (b). Now pull the drive complete away from the boat. (Reference: Section 2A, Page 7)
    Shift Cable Linkage Jaws

Check the Gimbal Bearing and Bellows (Click to expand)

Frequency: Every 200 Hours or Annually
Materials needed: None
Tools needed: None

  1. Using your fingers, reach inside the bell housing and rotate the gimbal bearing (a). It should rotate effortlessly with no rough spots. Also push and pull on it to make sure it does not move in any direction, other than to rotate. If you feel any movement, or any roughness in the rotation, have the bearing replaced by a professional. Also note the condition of the bellows (b). The bellows should be flexible, not rigid, and have no tears or cracks. If the bellows are in bad shape, or there is any water in there at all (grease is OK), have them replaced by a professional. (Reference: Section 4A, Page 27)
    Gimbal Bearing

Grease the Gimbal Bearing (Click to expand)

Frequency: Every 200 Hours or Annually
Materials needed: U-Joint and Gimbal Bearing Grease (92-802870A1)
Tools needed: Grease Gun

  1. Lubricate the gimbal bearing through the grease fitting on the transom assembly by applying approximately 8-10 pumps of U-Joint and Gimbal Bearing Grease to the grease fitting (a). (Reference: Section 1B, Page 23)
    Gimbal Bearing Grease Fitting

Check Engine Alignment (Click to expand)

Frequency: Every 200 Hours or Annually
Materials needed: None
Tools needed: Engine Alignment Tool (91-805475A1)

  1. Attempt to insert the solid end of the alignment tool (a) through the gimbal bearing (b) and into the engine coupler (c) splines. It should slide in easily with no force required (slides in and out freely with two fingers), and bottom out in the coupler. If the tool does not easily slide all the way in and out, the engine alignment is off. Have a professional adjust the engine alignment. (Reference: Section 1B, Page 27; Engine Specific Service Manual)
    Engine Alignment Tool Engine Alignment Tool Cross Section

Torque Steering Nuts (Click to expand)

Frequency: Every 100 Hours
Materials needed: None
Tools needed: Torque wrench, 9/16" socket (standard gimbal rings) or 5/8" socket (magnum gimbal rings)

  1. Torque the two nuts (a) at the top of the transom assembly to 55 lb-ft. These nuts secure a U-bolt to the steering assembly. If this is loose, not only do you loose some steering ability, but very expensive damage can occur. Trust me, I've been there. (Reference: Section 2A, Page 2)
    Steering Nuts

Lubricate Sterndrive and Replace O-Rings (Click to expand)

Frequency: Every 100 Hours
Materials needed: Bravo Installation Kit (16755Q1), Engine Coupler Spline Grease (92-802869A1), U-Joint and Gimbal Bearing Grease (92-802870A1), 2-4-C Marine Lubricant (92-802859A1), Special Lubricant 101 (92-802865A1)
Tools needed: Rags; Wire brush; Grease gun; Needlenose pliers

  1. Remove old O-rings and clean surfaces. The Bravo install kit comes with 6 O-rings. There are three on the shaft at the top of the drive (two thick and one thin), a thick round one around the shift cable linkage jaws, a funky shaped one around the water passage on the drive, and a small one on the bell housing (the part still attached to the boat) around the gear oil check valve. Find all of these and remove them. Try to remember what went where. As you remove each one, wipe off as much of the old grease in that area as you can, and then use a wire brush to clean up any corrosion in these areas. (Reference: Personal Experience)
    Bravo Installation Kit
  2. Grease the U-joints with a grease gun loaded with U-Joint and Gimbal Bearing Grease. There are two grease fittings (a), and they are a little tricky to get to. Apply approximately 3-6 pumps of grease, until a small amount of grease begins to push out of the bearings (b). (Note that "heavy duty" U-joints do not have grease fittings, so you cannot do this step.) (Reference: Section 1B, Page 26)
    U-Joint Grease Fittings
  3. Grease the O-ring areas (a). Using U-Joint and Gimbal Bearing Grease, grease the circle groove around the shift linkage jaws and the funky shaped groove around the water passage. Press the new O-rings into these grooves, and smear the grease onto the exposed O-ring surfaces. (Reference: Section 2A, Page 30)
    Sterndrive O-Rings
  4. Grease the shift linkage. Hold the shift linkage assembly (a) out as far as it will go with a pair of pliers. Grease the underside of the lower lip (c) with Special Lubricant 101. The jaws need to remain open (b) in order for the shift cable to reconnect when you reinstall the drive. (Reference: Section 2A, Page 31)
    Open Shift Cable Linkage Jaws
  5. Grease shaft splines (a) and the grooves (b) for the new O-rings with Engine Coupler Spline Grease. Don't be shy with the grease, you want the new O-rings to be able to slide all the way up into their groove, and you want plenty of grease on the splines for when it engages with the engine coupler. Slide the new O-rings onto the shaft one at a time, until they are all in place. Two identical O-rings slide all the way up to the top of the shaft (b), while the third goes right behind the splines (a). (Reference: Section 1B, Page 26)
    Shaft Splines And O-Rings
  6. Install the gear oil check valve O-ring. Press the new O-ring into place around the gear oil check valve (a). There is probably a little bit of gear oil in the groove that will hold the O-ring in place. (Reference: Personal Experience)
    Gear Oil Check Valve
  7. Grease bell housing studs. Using the wire brush, clean off any corrosion around the studs, and clean any dirt out of the threads. Rub a light coat of 2-4-C Marine Lubricant on the exposed area of the bell housing studs (a). This will help the nuts go on and off without difficulty, and help prevent corrosion. (Reference: Section 2A, Page 2)
    Bell Housing Studs

Install The Sterndrive (Click to expand)

Frequency: Every 100 Hours
Materials needed: 2-4-C Marine Lubricant (92-802859A1)
Tools needed: 5/8" socket, swivel, extension, and ratchet; 5/8" combination wrench; Torque wrench

  1. Install the sterndrive. Make sure the shift lever on your boat is in neutral. Lift the trim cylinders so that they stick stright out from the boat. With one hand, hold the shaft and guide it into the gimbal bearing. As you slide the sterndrive on, make sure the shift cable (b) engages with the shift linkage jaws (a). Make sure the trim cylinders stay on top of the cavitation plate as you slide the drive on! If they fall down you will have to pull the drive back off. As you get the drive almost all of the way on, you may have to rotate the propeller in order to get the shaft splines to align with the coupler. Once the sterndrive is in place, spin the prop to make sure the drive is in neutral. If the prop doesn't spin, the shift cable didn't engage the shift linkage jaws, so you need to pull the drive back off and try again. Once the drive is firmly in place, put the 5 washers and 6 nuts back on the bell housing studs. Remember that the center stud on the left side has a grounding plate (c) and doesn't get a washer. Starting with the center two, torque the 6 nuts (d) to 50 lb-ft. (Reference: Section 2A, Page 29-32)
    Shift Cable Linkage Jaws Bell Housing Nuts
  2. Install trim-in limit insert. There is a white nylon piece call the "trim-in limit insert" in the hole that you removed the anchor pin from. It may have moved around, so you need to check its position before reattaching the trim cylinders. On Bravo One and Bravo Two drives, the insert (a) goes forward, toward the transom. On Bravo Threes, it goes aft, away from the boat. (Reference: Section 2A, Page 33)
    Bravo One And Two Trim-In Limit Insert Bravo Three Trim-In Limit Insert
  3. Grease trim hardware and attach trim cylinders. Take the 4 black rubber bushings (b) and apply a liberal amount of 2-4-C Marine Lubricant to them, and insert them into the trim cylinder pivot ends (a) with the smaller diameter going inside the pivot ends. Apply a liberal amount of 2-4-C Marine Lubricant to the anchor pin, including the threads. Line up the trim cylinders with the hole that contains the trim-in limit insert, and begin inserting the anchor pin through one of the pivot ends. Apply a coating of 2-4-C Marine Lubricant to the 2 flat washers with the large holes. Place one washer between the bushing and the trim-in limit insert, and push the anchor pin through the washer and into the hole. As it emerges from the other side, place the other washer on that side. Center the anchor pin. Apply a coating of 2-4-C Marine Lubricant to the remaining two washers (c) and the two nuts (d). Place a washer and nut on each side of the anchor pin. Holding one nut with the 5/8" combination wrench, use the ratchet and socket to tighten the other nut. The nuts will bottom out when they reach the ends of the threads, so tighten until they stop. There should be plenty of thread left exposed to attach the 2 trim cylinder caps (e). Thread the caps on by hand. (Reference: Section 2A, Page 34)
    Trim Cylinders Installation
  4. Hook up the speedometer. If you had to disconnect the speedometer earlier, now is the time to reconnect it. (Note: If your speedometer had not been working previously, the passage in the drive may be clogged up. You can blow some compressed air into the passage (b) before hooking the speedometer back up to make sure it is clear of mud or debris.) Trim the drive way up, reach behind it, and insert the plastic fitting (a) into the hole it came out of (b). The fitting only goes in one way, so don't force it if it doesn't feel right. Once it is seated, rotate the fitting about a quarter turn clockwise so that it points toward the transom (c). This locks it into place. (Reference: Section 2A, Page 35)
    Speedometer Hose Fitting Installation

Paint The Sterndrive (Click to expand)

Frequency: Annually
Materials needed: Mercury Light Gray Primer (92-802878 52), Mercury Phantom Black Spray Paint (92-802878Q 1), Mercury Corrosion Guard (92-802878-55)
Tools needed: Wire brush

  1. Paint the sterndrive. I won't go into a lot of detail here, because the process could be very different depending on the condition of your drive. Assuming it is in good shape, with minimal corrosion, here is the minimum you should do. Take the wire brush and remove any corrosion you find, until bare metal is exposed. This usually happens first near the props and where the trim hoses connect to the trim cylinders. Anywhere that the paint has been scraped away may have some corrosion too. When this is all cleaned up, spray Mercury Light Gray Primer on all bare metal (but not the props). (Note: If you do not plan on replacing your anodes, be sure not to get any paint on them.) Then spray Mercury Phantom Black Spray Paint over the primer until the drive looks as good as you want it to. Follow the directions on the cans for temperature requirements and the amount of time required between coats. Apply as many coats as needed to get the drive looking good. Finally, spray Mercury Corrosion Guard on the entire drive to help prevent corrosion and keep the drive shiny. Again, read the directions on the can. (Reference: Section 1B, Page 8)

Grease The Propshaft (Click to expand)

Frequency: Every 2-4 months
Materials needed: 2-4-C Marine Lubricant (92-802859A1)
Tools needed: Wire brush

  1. Grease the propshaft. Remove the propeller(s), paying careful attention to how the nuts, washers, and spacers were installed. Apply a liberal amount of 2-4-C Marine Lubricant to the entire propshaft(s). (Note: if you have a Bravo I, do not reinstall the prop at this time, since it needs to be removed in order to change the gear oil in the next step.) Reinstall the propeller(s), replacing the hardware in the same order it was removed, and securely tighten the nut. Lots of people skip this procedure and don't perform it unless they have a real need to remove the prop, but as you can see above, this procedure is recommended every 2 to 4 months. Keeping up with this keeps your propshaft free of corrosion, making the prop(s) easy to remove when you have to, and also makes sure that the prop(s) are securely attached to the shaft and won't pop off when you least expect it. Either of these things could be really expensive and are easily preventable. (Reference: Section 1B, Page 24)

Change The Gear Oil (Click to expand)

Frequency: Every 100 Hours or Annually
Materials needed: Mercury High Performance Gear Lube (92-802854A1)
Tools needed: Large flat-head screwdriver, Gear Oil Pump

  1. Drain the gear oil. If you have a Bravo One, make sure the drive is trimmed all the way down, otherwise trim the drive all the way up. With the screwdriver, remove oil fill/drain screw (a). On Bravo Ones, this is on the aft end of the drive, beneath the prop. On Bravo Two and Three drives, the screw is near the bottom of the drive at the forward end. There is a washer (b) along with the screw. Sometimes it stays attached to the screw, and other times it stays in the hole. Keep track of it, you must reinstall it along with the screw or water will get into your drive. The top of the screw is a magnet. Inspect it for any metal. If there is a lot of metal stuck to the magnet, you may have an internal problem that needs to be checked by a professional. As the oil begins to drain, watch for water or milkiness in the oil. If you see any, have a professional test your drive for leaks and repair it. There is a vent screw and washer at the top of the drive. Remove this so that the oil drains faster. (Reference: Section 1B, Page 21)
    Bravo One Oil Fill/Drain Screw Bravo Two And Three Oil Fill/Drain Screw Oil Vent Screw
  2. Fill the gear oil. Once the gear oil is completely drained, make sure the drive is raised or lowered so that the propeller shaft is level. Hook up the pump to the oil fill drain hole, and pump until an air-free stream of oil flows from the oil vent hole at the top of the drive. At that point, install the washer and screw in the oil vent hole. Continue pumping until gear oil appears in the gear oil reservoir in the boat. Disconnect the pump and replace the washer and screw in the oil fill/drain hole. Top off the gear oil reservoir. Later, after running the boat in gear, be sure to check the reservoir and top off if necessary. Gear Oil Capacities are as follows:
    Bravo One: 88 oz - 2.75 quarts
    Bravo Two: 104 oz - 3.25 quarts
    Bravo Three: 96 oz - 3 quarts
    If you pay someone to do this for you, and they try to charge you for 4 quarts or more, they're ripping you off! (Reference: Section 1B, Page 3, 20-21)

Replace The Anodes (Click to expand)

Frequency: When existing anodes are corroded to 50% of their original material.
Tools needed: 5/16" socket, 7/16" socket, swivel, extension, and 1/4" ratchet; 3/8" allen wrench

  1. Replace the anodes. I'm not going to go into a ton of detail in this final section, because the procedure is pretty self-explanitory, and varies among drives. Basically you want to remove your old anodes (a) and replace them with new ones. Be sure to use new screws and don't forget to use the star-shapred continuity washers as well. There is debate about what anode material should be used, and it varies based on the salt content of the water your boat is in as well as other factors. I prefer Aluminum anodes, but Magnesium is very popular, with Zinc being the third option. All Bravo drives have a plate anode on the forward end of the drive, a round anode underneath the cavitation plate above the prop, and one on each trim cylinder. Bravo One drives also have an anode behind the prop, and the prop must be removed to replace it. Bravo Three drives manufactured from 2003 on have an additional anode on the end of the prop shaft. The props do not have to be removed to replace this one. Following are pictures of the anodes that are common to all Bravo drives. (Reference: Section 7A, Page 7-11)
    Anode Plate Trim Cylinder Anodes Cavitation Plate Anode Bravo One Anode