Mercruiser MAG 350 MPI Bravo to Alpha config swap

[ksliger]

Greetings,

I have a 1989 Arriva 2050 that I am restoring and repowering. I have removed the original Mercruiser 5.0 LX and purchased a 2002 MAG 350 MPI that I got a good deal on. The problem is that the new engine is setup for a Bravo drive. To keep my costs reasonable I am trying to figure out what all I need to do in order to change this setup from Bravo to Alpha so that I can utilize my current Alpha gen1.

So far I have figured out that I can remove the Bravo seawater pump and get the Alpha serpentine belt. After doing this I can get the water hose for the Alpha setup that goes from the transom to the power steering cooler. As far as I can tell these things will be all that is needed to change over the cooling system from Bravo to Alpha.

Also, from what I can determine, the Bravo coupler should work with the Alpha drive.

What I am stuck on and need guidance with is the shift interrupt configuration and the ecm. Is it possible to simply just change out the shift interrupt assembly from Bravo to Alpha or will my ecm need to be reprogrammed for Alpha? Are there any other solutions?

Finally, at the end of the day would it be cheaper to just find a nice used Bravo 1?

Thanks in advance for your replies!

Ken

 

[HT32BSX115]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

Finally, at the end of the day would it be cheaper to just find a nice used Bravo 1?

You can easily sell your Alpha. I don't think it would be "cheaper" but it would certainly be BETTER to get a bravo drive assuming you're getting the gimbal too. (if you do you may have to drill 2 more holes in your transom for the 2 additional studs in the Bravo gimbal. (A bravo drive WILL NOT bolt to an Alpha gimbal). If you have to buy a Bravo gimbal.....it will be more expensive

I see a LOT of Bravos on ebay and if I had a choice it would always be a Bravo.


Cheers,


Rick

 

[ksliger]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

Thanks for the reply. I am certainly considering this as an option. Right now just trying to determine if it is feasible and cost effective to change over the new engine to an Alpha setup.

 

[jtybt]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

Having done the alpha to bravo swap, I can tell you nothing is interchangable...except the coupler. It's an expensive and involved swap....but is worth the trouble.

The accepted rating of the alpha is 300 HP though I know people that have stuck a 383 in front . Just be care full going to full power. The biggest danger to the gears is shifting before the engine comes down to idle and really clunks the gears. These gears become compromised and are more susceptible to failure with the increased power of the mag engine.

 

[erikgreen]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

If you really have an alpha I gen I you can't use it with the bravo drive setup at all. Converting it to work somehow will NOT be cheaper or easier.

They're different enough in the small details that it's like trying to use an alpha drive on a Volvo Penta transom... it just won't work.

Sell the alpha and get a bravo type drive.. if you can find one to repair I think SEI can sell you a new aftermarket half to go with it, that's cheaper than a new or used mercruiser bravo.

Erik

 

[wca_tim]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

So your situation is that you've got the entire alpha drive and transom assembly working and in the boat, and you bought a 350 mpi that came from a different boat, but was set up for a bravo drive, correct? if that's the case, I'm not seeing how this is going to be hard. You have pretty much everything you need between what comes off the old 5.0 and what came with the new engine. the pulley and belt set-up from the old engine should work on the new one... and i would be surprised if there isn't a standard way to connect the shift interrupt mechanism you have to the new engine...

...Didn't the 350 mpi come standard in front of a lot of alpha drives as well? I would wager that the corresponding service manual will tell you most everything you need to know. I do know off the top that some bravo couplers will work with some alpha drive set-ups, but it depends on which belhousing? flywheel? coupler? combination (I don't remember right off the top). if it fits, it fits...

Don't know all the details, but that's where i would start...

 

[ksliger]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

Having done the alpha to bravo swap, I can tell you nothing is interchangable...except the coupler. It's an expensive and involved swap....but is worth the trouble.

The accepted rating of the alpha is 300 HP though I know people that have stuck a 383 in front . Just be care full going to full power. The biggest danger to the gears is shifting before the engine comes down to idle and really clunks the gears. These gears become compromised and are more susceptible to failure with the increased power of the mag engine.

Thanks, so are you saying that if I can get everything else working and changed over that I dont need a shift interrupter as long as I bring the engine down to idle before shifting?

If you really have an alpha I gen I you can't use it with the bravo drive setup at all. Converting it to work somehow will NOT be cheaper or easier.

They're different enough in the small details that it's like trying to use an alpha drive on a Volvo Penta transom... it just won't work.

Sell the alpha and get a bravo type drive.. if you can find one to repair I think SEI can sell you a new aftermarket half to go with it, that's cheaper than a new or used mercruiser bravo.

Erik

Erik, I think I have figured out all of the details except for the shift interrupter and how/if it interracts with the Bravo programmed ecm. I am trying to determine if there is an easy way to change this over to an Alpha perhaps by just adding the shift interrupter assembly from an Alpha. I just dont know if that will work on the current ecm.

So your situation is that you've got the entire alpha drive and transom assembly working and in the boat, and you bought a 350 mpi that came from a different boat, but was set up for a bravo drive, correct? if that's the case, I'm not seeing how this is going to be hard. You have pretty much everything you need between what comes off the old 5.0 and what came with the new engine. the pulley and belt set-up from the old engine should work on the new one... and i would be surprised if there isn't a standard way to connect the shift interrupt mechanism you have to the new engine...

...Didn't the 350 mpi come standard in front of a lot of alpha drives as well? I would wager that the corresponding service manual will tell you most everything you need to know. I do know off the top that some bravo couplers will work with some alpha drive set-ups, but it depends on which belhousing? flywheel? coupler? combination (I don't remember right off the top). if it fits, it fits...

Don't know all the details, but that's where i would start...

Tim, you have the situation correct. I have a working Alpha One Gen 1 drive and a 2002 MAG 350 MPI setup for a Bravo drive. I have figured out how to deal with the pulley situation. I am really just stuck on the shift interrupt and ecm part. I need to know exactly how to do this. I know that I can swap out the current Bravo ecm with an Alpha one but that part is 1800 bucks, ouch!

 

[Don S]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

It would help to have a SN for your 2002 engine, but here is a list that should be close to your range. As you my notice, those ECM's are designed for specific drives. I think there was a Service bulletin on them, but not sure what engines, that the Bravo ECM when used with an Alpha cause a problem of not getting over 3000 rpm or something like that.
Post your SN, then we can track down what will really work.

 

[ksliger]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

Thanks Don, the s/n for the 2002 MAG 350 MPI is 0M333397

 

[jtybt]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

You need the interrupt switch if you use the alpha.

 

[ksliger]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

OK , but if I just order that switch and add it do you know if the current Bravo ecm will work correctly with it?

 

[Don S]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

OK , but if I just order that switch and add it do you know if the current Bravo ecm will work correctly with it?

You need the correct ECM, (PN 865838T03). The Bravo ECM does not have any options to use the shift interrupt system.
The good news is the wiring harnesses for the engine is the same and used on both Bravo and Alpha drives. So there will be terminals for the switch.

 

[Fishermark]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

I did a similar switch a few years ago and decided to keep the engine mounted pump and install a through hull pick up. You will get more volume of water with the engine mounted pump and better cooling than with the pump in the alpha 1. If you go that route you can keep the pump in the outdrive (to help cool it) and simply re-route that water back through the back of the boat. Here's a pic of what I did - you can see the strainer on the left side of the picture - that hose leads to a valve and 1.25" thru hull fitting:

 

[ksliger]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

You need the correct ECM, (PN 865838T03). The Bravo ECM does not have any options to use the shift interrupt system.
The good news is the wiring harnesses for the engine is the same and used on both Bravo and Alpha drives. So there will be terminals for the switch.

Thanks Don. I was afraid that would be the case. Are there ways to just reprogram the existing Bravo ecm that I have? Also, if I decide to just upgrade my drive to Bravo (looking more like what I will do) will any year work with this engine?

I did a similar switch a few years ago and decided to keep the engine mounted pump and install a through hull pick up. You will get more volume of water with the engine mounted pump and better cooling than with the pump in the alpha 1. If you go that route you can keep the pump in the outdrive (to help cool it) and simply re-route that water back through the back of the boat. Here's a pic of what I did - you can see the strainer on the left side of the picture - that hose leads to a valve and 1.25" thru hull fitting:

Thanks thats a great idea! How did you deal with the switch interrupt issue that I am currently faced with?

 

[Don S]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

Are there ways to just reprogram the existing Bravo ecm that I have?

Nope

if I decide to just upgrade my drive to Bravo (looking more like what I will do) will any year work with this engine?

Yes, it should. Just remember one thing, you need EVERYTHING. Transom shield (inner and outer), Exhaust Y etc. Not just a drive.

 

[ksliger]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

OK Don thanks again! I have found a few deals already on complete used Bravo assemblies that include Inner and outer transom plate, gimbal ring, bellows, pistons and drive. I had thought that my existing exhaust y-pipe would mate up. Is that not the case?

 

[Fishermark]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

How did you deal with the switch interrupt issue that I am currently faced with?

Can you not simply use the shift plate from your current set up?

 

[Don S]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

Can you not simply use the shift plate from your current set up?

That is not the problem, the problem is the ECM will not understand what a shift interrupt switch will do. Bravo's don't have them, so the ECM isn't set up for one.

 

[Fishermark]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

Ah - got it.

It's funny, but I seem to remember that the engine I have pictured above was set up for a Bravo drive when I bought it. It has the engine mounted pump with the Thunderbolt V ignition. I bought it as a complete bobtail package. I told the company I bought it from what I intended to use it for... I never thought about the interrupt switch situation. They must have done whatever modifications were necessary for me when I bought it.

 

[Don S]

Re: Mercruiser MAG 350 MPI Bravo to Alpha config swap

They must have done whatever modifications were necessary for me when I bought it.

No, you don't modify if OEM, you just ask for what you want and they give you the proper engine.