Basic Bravo Drive Service / Volvo Duo Prop Service
Be sure to also read the Alpha Basic service blog as there are details that will cross over and apply.
Bravo drives are easily identified by their size, Bravo drives are much larger in size and are most identified with duo prop configuration. There are three common generations of Bravo drives. The first is the single prop bravo drive most common on boats from the 1980's, single prop drives are similar in service to the alpha drive only larger in size. It is the two Duo prop generations that we want to focus on in this service information. The reason why I have included the Volvo Duo Prop drive with the Bravo Three duo Prop are they are very similar to complete a basic service on.
There are some specialty tools you will need to purchase from your mercury or Volvo dealer to complete service. this is because the gear oil drain is located behind the props.
1- Prop Nut socket kit from Mercury Marine (Mercury will not fit Volvo)
2- Prop Nut Socket kit from Volvo Marine (Volvo will not fit Mercury)
3- Large straight screw driver for vent screw (Mercury)
4- Large set of metric Alan wrench's for drain screw (Volvo Marine)
5- 5 one liter bottles of High Performance gear lube (Mercury Marine)
6- Volvo synthetic Gear lube from Volvo, you must use the synthetic gear lube in your Volvo drive do not use Mercury High Performance
7- Mercury Zinc Chromate primer (Mercury Marine)
8- Mercury Phantom Black Spray paint (Mercury Marine)
9- Volvo zinc Chromate primer (Volvo Marine)
10- Volvo silver color match drive paint( Volvo Marine)
11- Anode replacement kit for either Mercury Bravo Three Drive or Volvo Duo prop drive( you may require the drive serial number to be sure you get the correct parts. For Bravo Three you will locate the drive serial number on the top motor cover. On a Volvo you will locate the serial number for the drive on the motor cover.
12- Mercury 2-4-c grease this can be used on either drive.
13- Grease gun with underwater grease by either Mercury or Volvo.
In either drive service case you will need a oil recovery container (oil drain pan). You will also need a one foot cut length of 2x4 to use as a prop wedge. The first step is to remove the props. Trim the drive down to a comfortable position to access the prop nuts and remove the props. Place the 2x4 wedge in between the edge of the large prop and the anti cavitation plate above the prop so the props cannot turn when you apply pressure with the correct prop nut socket on the small prop. These nuts may be very, very tight, they loosen by turning to the left. Once the small nut is removed you may find the prop tight to pull off, place a wooden block against the back of the prop on of the back of the blades and give the block a hit with a mallet, do not smash the block simply work your way around the blades until the prop pops off. Do not let the prop fall on the ground they are finally tuned stainless and can be bent with a fall onto concrete or hard surface. This will expose nut number two the large prop nut . Place the 2x4 in the same location between the end of the blade and the anti cavitation plate and loosen the same way. Once nut is removed take off the prop.
You will now be able to see the drain screw in the very bottom of the bullet or gear case facing you. You will now need to trim the drive all the way down with the oil change tray under the drive, with the skeg set over the middle of the pan. You will then remove the drain screw which will have a small ring gasket on it. Then you will remove the vent screw which will be on the side of the gear case up high on the right hand side of the case. If you have a Volvo Duo Prop drive you can also remove the dip stick which is in the top middle of the gear case it looks like a large bolt with a slot for a screw drive in it. Now you will need to leave the drive for a couple of hours to completely drain down, this will also drain the reservoir bottle on the engine at the same time. Do not rush this.
While this is going on its time to inspect the condition of the drive and the anodes. If the anodes show any bad break down or are missing install new ones, the kit will provide you with details of were to look for all the anodes that can be serviced. If you have areas were the paint is damaged then you will need to re spray and paint in these areas . Do not unless absolutely necessary sand and paint the whole drive. If you do this you are starting a process that will never end you will be painting the drive every year., the products that the drive was coated with from the factory are the best and are almost impossible to reproduce. Once you sand the drive you are immediately promoting corrosion. Do not paint any anodes they will not work if they are coated with paint. If you paint the anodes the props will become your anodes!
When you are sure that all the gear lube is drained it is time to refill. Hook the gear oil pump up to the drain screw hole and begin to slowly pump gear oil into the drive with the large duo prop drives stop every five minutes and let the air get on top of the lube, a two min break is good enough and then continue to pump slowly until the gear lube is showing at the vent. Now leave every thing hooked up and take a ten minute break, come back and pump a little more until the slow flow out of the vent screw hole is steady with no air sputtering. Now you are full. Grab the drain screw and install a new seal ring and do the same to the vent screw. Install the vent screw (and in the case of a Volvo put the dip sick back in finger tight). Now remove the gear lube pump and replace the drain screw.
and the vent screw. In the case of the Volvo Duo Prop you can confirm the gear oil level with the dip sick and then replace and tighten the dip stick.
With the drive full of gear oil you must now go into the boat and fill up the reservoir on the engine . On the first trip you must recheck the level in this reservoir and if it drops some top it up. This is important and like the alpha reservoir there is a sensor and alarm on this bottle, if the gear oil level goes down to a low level it will send you a signal by providing a constant beeping at the dash when the ignition is on. I noted in the alpha service blog that the reservoir must be connected through the wire harness, if the sensor is not plugged in or the wires are modified get them fixed. Without this warning you will not know that the drive is consuming gear oil and the worst case the drive will blow up. If through the year you need to keep filling the reservoir then contact your authorized service provider and have them do a pressure test on the drive, and have the drive fixed if gear oil can escape then water can get in. This is a recipe for disaster.
On a Bravo Three Drive or the Volvo Duo Prop it is important that the trim up and down is smooth and even , If the drive trim is slow to react or the drive jolts on the way up or down you will need to grease the trim ram pins there are two one at thee front of the rams and one at the back, the way to do this is to remove the plastic end fitting on the ram pin, under this you will find either a nut or a clip remove one side and slide the pin out of one ram side only place some grease in the hole and slide the ram back in and reverse the procedure for the other side. try to do one side at a time if you remove the whole pin then you need to man handle the drive back into place to slide the pin through all the holes. In the case of a Mercury Bravo Three there is a yellow plastic spacer in the drive itself that must be re installed the correct way or your drive will not trim all the way down. In most cases this job can be a little intimidating and you may want to let your service provider handle this.
There is no sea water pump in a Bravo Three or Volvo duo prop. So gear oil change, placing some grease on the prop shafts, a little paint, anodes and your basic service is done. If you see any zirk fittings for a grease gun to hook on give them a couple of pumps of grease and away you go.
Things you must be aware of with Bravo Drives:
1- Do not operate the shift unless the motor is running, all you are doing is stretching the shift cable
this will cause shift problems.
2- If you have Bravo Three drives and are a fishing nut then you are likely stressing the universal joints and should have the drive pulled every year to keep an eye on the universal joints.
3- Gear oil changes are key to the drives ability to sift because of the cone clutch.
4- If you run fast a lot with the Bravo Drive the bearing at the very top of the drive gets hot and will burn up, there is a kit you can buy that pick up water and dumps it on the top of the drive to cool the housing and bearing, if you are running long distance it is a good idea to slow down and let the top of the case wet down and cool occasionally.
Example of a Bravo Shower
5- Keep your props in good shape if you run with banged up props it is hard on the prop seals.
6- Set out a service schedule were you have the drive pulled at regular hourly operation times or annually for drive shaft, bearing and bellows inspection and service.
7- If you have damage to the skeg or cavitation plate get this fixed, the aerate water around the props will be disturbed and you will loose performance (this is true for any drive)
8- If when you drain the gear lube the gear lube looks like a milk shake or has any water in it call your service provider and have them pressure check the drive.
9- Always replace the ring seals at the drain and vent screws after any service.
Mercury Duo Prop Tool
Things to be aware of with Volvo Duo Props:
1- You actually loose less horse power through a Volvo drive.
2- You have a dip stick in the top of the drive to check fluid level after you change the gear oil.
3- Under the front cap of the drive There is the shift shaft this are should be lubed up to prevent corrosion, as there is a seal here that can allow water into the drive and if it is not lubed can create stiff shifts.
4- You must use Volvo synthetic fluids appropriate for your application.
5- If you are buying parts for your Volvo Duo Prop be sure of the serial number, and only by genuine Volvo parts as after market parts quite often will fit but are not exactly right and you will be repairing again in a season,
6- Do not try to remove the props without the right tool if you knock off any of the raised bumps on the nut you will end up having to cut the nut off.
7- Arrange with your service provider regular dive pull service to inspect the drive shaft, bearing and the bellows this should be based on hours of operation or annually.
Volvo Duo Prop Tool
When we discuss service based on hours the standard is usually every 100 hours of operation or every year. A key fact is that most Inboard /Outboard boats that sink ,the cause is the bellows. The bellows are the rubber boots which surround the drive shaft and the shift shaft, some drives have exhaust bellows also. With age these bellows begin to crack and water starts to trickle in, a dead give away for bellows that are going bad is when the drive is pulled and there is water in the bellows and or the drive shaft is all rusty. Because of the proximity of the bellows to the water (under water) this is a repair you should have an insured and certified service provider complete the installation can be tricky and requires experience . Done wrong and your boat is on the bottom. This is why it is recommended not to store the boat with the drive trimmed up for long periods of time, if you have muskrats in your area they love to chew on the exposed bellows. So keep your drive in the all the way down position as much as you can.
Example of Bellows Kit
Never attempt a repair that you feel is over your head if you require detailed service information Email: boatnutmedia@gmail.com and we will help you with any questions you may have.
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