Bravo 2 water pump impeller

[woodguy81]

So I just purchased a boat with twin 5.0 mpi engines with bravo drives. My other boat has the same engine with an alpha one. Does the bravo drive have an internal impeller like the alpha one or is it just the water pump on the engine that needs service? What differences are there between the alpha and bravo drives? I was told the boat has bravo 2 drives. I’m not sure how to tell.

 

[achris]

Bravos only have an engine driven seawater pump (which isn't the engine water pump). No impeller in the drive.

Go to Mercs website and read the sales blurb on the different drives to give you an idea of the differences.

Internally, put simply, an Alpha shifts in the gear housing, a Bravo shifts in the drive shaft housing.

Chris....

 

[woodguy81]

Thanks. So the water pump mounted to the bottom left of my engine serves the same purpose as the impeller in the alpha drive. then it also has the circulation pump that is part of the motor. These also have the closed cooling system. Not sure that’s the correct term but it’s got a sort of heat exchanger with antifreeze in the engine. Can you direct me to a cooling and electrical diagram for this motor? Both engines need some work.

 

[Bt Doctur]

If the engines are original there is a small aluminum tag just above the starter
post that number so we can figure out the year at least.

 

[achris]

Thanks. So the water pump mounted to the bottom left of my engine serves the same purpose as the impeller in the alpha drive.

Yes. But use the terms 'port' and 'starboard' rather than 'left' and 'right'.

then it also has the circulation pump that is part of the motor. These also have the closed cooling system. Not sure that’s the correct term but it’s got a sort of heat exchanger with antifreeze in the engine.

Yes, it's called 'closed cooling'.

Can you direct me to a cooling and electrical diagram for this motor? Both engines need some work.

With an engine serial number, yes. (Read BT's reply above.)
If you're not sure where to find the serial number, look through the stickies at the top of this forum and you'll find a document on where to look.

Chris......

 

[Scott06]

So I just purchased a boat with twin 5.0 mpi engines with bravo drives. My other boat has the same engine with an alpha one. Does the bravo drive have an internal impeller like the alpha one or is it just the water pump on the engine that needs service? What differences are there between the alpha and bravo drives? I was told the boat has bravo 2 drives. I’m not sure how to tell.

In addition to other comments main difference between bravo and alpha drives is the shifting mechanism. alpha uses a dog clutch which produces a clunk when it shifts into gear. Bravo uses a cone clutch which will provide smoother operation.
also bravo drives are heavier and can take more strain than an alpha. Generally are used on heavier boats with larger engines as the bravo can handle more power and boat weight than an alpha.

bravo two has a straighter and deeper lower unit than the other bravo units to allow for larger diameter propellers

 

[dubs283]

I was told the boat has bravo 2 drives. I’m not sure how to tell.

There are four different fundamental styles of bravo drives. Bravo 1, Bravo 2, Bravo 3, and Bravo 4S.

Bravo 1 and 2 drives have one propeller, 3 and 4S have 2 counter rotating propellers. Bravo 3 props are aft facing and 4S props are fwd facing.

The main difference between Bravo 1 and 2 drives is the size of the gear case. Bravo 1 gear cases are smaller than Bravo 2 gear cases and the later style Bravo 1 has a raked shape to the exhaust housing as in the angle of the case on the trailing edge above the prop to the cavitation plate angles aft ward.

Bravo 2 drives are mainly used for commercial heavy duty applications and on larger hulls with deeper drafts that are designed for a maximum speed of 40 mph.

It is In your best interest to obtain the correct oem manuals for your engine and drive. Bravo manuals are numbered 11, 28, 39 and the latest models are covered in the aptly named "Service Manual - Bravo Drives" As far as your engine, as stated above find and post your serial numbers and folks here can quickly guide you to the correct manuals for your setup

FYI I have yet to see a Bravo 4S in the field, however they are specifically designed for surf boats (hence the "S" designation) and most likely would not be used in a twin engine setup

 

[woodguy81]

Thanks for all the info. I’ll try to get serial numbers. Motors are 2005 according to the stickers on the ecu plates. Boat is a 95. So not original to the boat. I gambled I purchased in non running condition. I’m confident I can make them run. Just my other boat is an alpha drive with the raw water cooling system. Otherwise these are the same.