Alpha To Bravo Conversion
After grenading two alpha's on my stock powered 18 Donzi I had enough. I wanted to regain the strength and smooth shifting I had with my original Volvo yet retain the modern power trim, power steering and parts availability of the Alpha. With everything on hand this is a long weekend project but yields great results. In this page I will outline the specific Alpha to Bravo conversion issues. This page will NOT cover mercruiser basics such as engine removal and alignment.
The first thing you need to do is remove the alpha one and then take out the engine. Then remove the intermediate housing. The alpha uses 6 bolts/studs that go through the transom. The bravo requires two more holes to be drilled in the transom. To locate these holes you need the mercruiser template or if you do not have this ( as I did not) it is easy enough to make your own cardboard template off the Bravo intermediate housing.
After drilling these holes the intermediate housing can be mounted. After bolting the inner plate to the intermediate you can re install the alpha steering ram. The ram from an Alpha application is the same ram as it is for a Bravo application.
The bravo, unlike some alpha's, has an inner drive oil bottle. This will need to be mounted on the transom or engine.
Also the Alpha has an internal raw water pump. The bravo does not have this pump and while then engine is out you are going to have to add either a crank driven or a belt driven one to the front of the engine. Also keep in mind that the inlet diameter of the Bravo water line is 1 1/4". That alpha is 1". the inlets on the raw water pump you just added are most likely 1 1/4". The only problem created is that if you engine has an oil or power steering cooler the inlet and outlet will be the 1" originally from the Alpha. You can either chose to reduce the raw water line into the cooler and then step up in size after but I personally do not think that is the correct way to do it. I would recommend after going to all this effort and expense to get the appropriate diameter cooler.
The wiring for the trim switches remains the same. The wires that go the the shift plate can now be disconnected as the Bravo does not need the shift interrupt to come out of gear. If you have added the drive oil bottle the two wires that come out of the bottom of it are a low level indicator. You can either chose to hook these up or go without the low level warning.
That should be the majority of it. It is a very simple swap with no custom fitting, grinding or machining needed. All that is needed to do the job is the most basic hand tools and a Mercruiser alignment tool.
I have been very pleased with the swap and so far the drive has been bulletproof. I am very pleased with it's overall performance and recommend it highly.