Converting engine from Bravo setup to Alpha setup
 

Considering repowering my boat with a 350 MAG MPI. I know these where typically used in a bravo applications. What would need to be changed to make it work with an alpha setup, I know the engine driven impeller needs removed but is there anything else that needs changed? What's the best way to delete the bravo style impeller without screwing up the belt routing?

I would leave the belt driven raw water pump on the engine and remove the impeller from the Alpha's pump. It's a much larger and better pump than the Alpha pump.

oh, convert engine, not boat. the easiest way is to use the brackets, alt, pwr steering from your old motor. I assume it is also small block. is your current engine MPI? if boat is not MPI, did engine come complete with ecu and harness? otherwise swapping to your carb is easiest way to go. if you run the bravo raw pump, the hose from the transom to pump MUST be changed. it will suck an alpha hose flat. they are not made to handle suction.

I didn't realize that was an option, makes things much easier. Does the inlet hose need changed for that to work properly?

Why not keep the bravo and have a bullet proof setup?

^^^I thought the same...but now thinking he has an alpha on the boat already and is putting in the 350MPI. The 350 MPI came with Bravo equipped boats.

correct. I currently have a carb 350 mag and alpha gen 2. Don't want fool with changing the drive out but would like to swap the engine to 350 MAG MPI.

Okay, did some digging, the 350MPI's could come with Alpha's.

Looking at pic below,For Bravo equipped, #27 hose is from transom to Bravo sea water pump. #26 is from Bravo sea water pump to the inlet of oil cooler.
Direct link with part #'s, prices, and the diagram: Genuine Mercury & Mercruiser parts. STANDARD COOLING SYSTEM

For Alpha's, since these drives have pump in the drive and do not use a engine belt driven sea ater pump, #10 is hose from transom assembly to front of oil cooler.

I'll look for belt difference between Bravo and Alpha in a minute.

http://www.mercruiserparts.com/Merc/...MMON/35471.gif

Okay, on Genuine Mercury & Mercruiser parts. WATER PUMP AND FRONT COVER they list 3 different belts. 1 is for Alpha and 1 is for Bravo and why a 3rd ? However, it doesn't say which belt is for what drive.

Cruising thru other look-ups:
Loks like #57-861758A1 is for the Alpha equipped.
Looks like #57-861757A1 is for the Bravo equipped.
Looks like #57-861049A2 is for 4.3L v6 boats...why this is on that page as an option I don't know.

So....I did this quickly and it's your boat not mine, so please do your homework still and don't 100% go by what I found.

most definitely. Thanks for the help. You got me going in the right direction.

Also not opposed to running the bravo impeller pump on the alpha if it's possible. What would need to be changed other than the inlet hose mentioned above? I'm also assuming you have to remove the impeller from the housing within the alpha itself

Yeah remove the impeller in the alpha and route a non collapsable hose from the transom to the sea pump intake.
Also need to use the shift interrupter from the alpha setup. The older ones ground the coil, newer one may be different, cant remember, but you will need it.

Does the 350 MPI have a provision in the ecm for shift interrupt switch?

Chris

Take a look at the little magnifying glass, there are notes describing the application for each one.

The bravo version does not, that is one of the obstacles. Mercury does offer a 350 MPI Alpha engine as part of the reman program.

Awesome ! Thanks. You learn something new everyday. :)

If you are going to use an ALPHA GEN 2 outdrive you can NOT use a bravo impeller set up unless using a water pick up instead of the drive water inlets.

., And for all --- the Gen 2 Alpha impeller and housing is more bullet proof than any bravo housing and impeller. The alpha gen 2 impeller is called a floppy vane impeller and I have seen people never change it with the darn engine still pumping water like crazy. The longest alpha gen 2 impeller and housing ( in which is heavy duty stainless steel with a pretty thick wear plate on the bottom ) in use was 12 years straight. I could not believe it if I did not see with my eyes. I do not recommend ever doing that period. Just saying.

The Alpha impeller set up does not pump as much water volume as the Bravo set up,

Lots of good info here. Thank you everybody. I did find the Alpha and Bravo versions of the 350 Mag Mpi on mercs reman website. To me, it seems easier just to buy the engine for the correct application instead of trying to change things and make it work. If decide to do it I'll keep everybody posted through the transition process. Now for the most important question, how much speed will be gained from the old engine to the new? Boat currently runs a best of about 57mph with a carbed 350 Mag.

The interrupter switch can be added to use the Gen 2 provided your using the EST distributor. Need to change the switch from a NO to a NC switch. If motor has the HVS distributor, don't think it will work, but might, I would need to dig some more.

As for speed, it takes a lot of HP to increase above boat efficient plane speed, and will leave that to others

Play with this, it has been quite close for a few boats I work on. Single engine.

Desired Speed² / Current Speed² = Y

Y x Current HP = HP needed to go Desired Speed.

My guess is 60 ish

I'm guessing 63-64. Guy I know has a boat same as mine and he runs 64.7 with a 350 mag and bravo

changing over to a alpha from a bravo then using a good matched prop with the alpha Gen 2 will be fast 2 mph faster min than a Bravo.

Possible I am not reading some of these posts correctly but I will add correct info to clearify. There is 1000s of ECM 555 -- MPI 350 MAG with HVS ignition set up with shift interuptor switch using an Alpha GEN 2 outdrive in OEM stock form. sold brand new from 2001 to 2010 NON Catalyst engines.

here is just some of the serial numbers runs of the 350 MAG MPI Alpha GEN 2 in the link below as an example --- also there is the MPI 5.0 and the MPI 4.3 with the HVS ignition and shift interuptor switch using an Alpha GEN 2 in the 1000s as well.

MerCruiser 350 Mag MPI Alpha / Bravo Engine & Stern Drive by Component

and here is the more current serial number runs NON Catalyst MPI 350 mag with HVS / ecm 555 Alpha gen 2 outdrives. Like I said there is 1000s of them out there

http://www.marineengine.com/parts/me...vo/1a611928-up

so you have a 350 carb alpha boat that currently runs about 57 mph? and you want to do all this converting and replace the engine for a couple 3 mph more? what is this engine gonna cost? 3 to 4 k? and as soon as you have enough power to hit mid-60's you are gonna wish that alpha was a bravo. but if you really want to hop up that boat, I would consider a re-ring on that block and upgrade heads-intake-exhaust-cam on it. fuel injection is not by definition faster or more powerful than a carb.

wont have to convert anything now that I know they make an alpha ready version if the MPI. I built a carb 350 for my last boat. While it would be cheaper it's a lot of work, same as if I tear mine down and re ring it and freshen it up. Wife is also showing interest in driving the boat as well and the idea of hit the key and go is appealing.