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Mercruiser MPI conversion 1991 305

B

bicounty

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I have a 91 Volvo Penta with a blown 305 with a 2 barrel carb . I want to re-power with a 350 vortec. I picked up a Mercruiser fuel injection set up off of a 2002 Mag 350. When I say fuel injection set up I mean I have a complete intake manifold with injectors,throttle body,tps sensor,distributor, coil, timing cover,crank sensor, wiring harness and a ecm555 computer. The only thing I don't have is the cool fuel pump and fuel lines. I am ready to order the motor and manifolds and try to put this Frankenstein together. I have found a few Merc Cool Fuel Pump setups on ebay but I am not exactly sure on how this should be set up. I am planning to have the stock Johnson raw water pump running off the crank then run the raw water to the fuel cooler then to the heat exchanger. As far as the fuel lines go, does the line from the fuel tank go to the fuel pump or to the water separator first. From what I understand Mercruiser Mag MPI have no return line to the tank but the return line runs to the water separator. Can I use the regular carb style water seperator or is there a special water separator mpi application. Looking at the Cool Fuel pumps on Ebay and looking at parts drawing it looks like the fuel pumps have a fuel inlet and outlet to the fuel rail and a return from the regulator to the water separator. The fuel rail on the intake manifold has fuel inlet and a return line fitting. That would give me 2 return lines (one from the pump and one from the fuel rail). Can anyone out there straighten me out on how the fuel lines are set up? Thanks
 
Re: Mercruiser MPI conversion

I don't believe that you will be creating a "Frankenstein" if you were to use and follow the Mercruiser design and use all of the Mercruiser components. Your Volvo Penta drive won't know the difference.

I don't know enough about this, but I'd make sure that there is no MPI system "interface" for an Alpha drive "SI" (shift interupt). It is unnecessary with Volvo Penta cone clutch gear engagement.

NOTE: Since M/C has many model changes and designations...., be sure to use the OEM Serial number from the engine that this MPI system was removed from.
You may want to permanently place this info somewhere on your engine.
Someone else may end up owning this boat some day, and it could be frustrating if they were not aware of the Non-Volvo Penta OEM system.

I'm thinking that the fuel cooler unit would be installed in the incoming "suction" side of the sea water path, rather than after the sea water pump.... Yes/No?
This is an Example ONLY for p/n's and parts description.
(see the correct OEM schematic by engine serial number)



It would appear that the fuel filter base would be a pretty standard four (4) port base.
Again, this is an Example ONLY for p/n's and parts description.
(see the correct OEM schematic by engine serial number)

I see nothing wrong with what you are doing if you were to bring it back to Mercruiser OEM original, or make changes that you know have been done successfully by others.
You've certainly asked the right questions. There may be a few more.

Have you thought of a name yet for this Bastard Child?
Merc-Penta?
Volvo-Cruiser?
Verc-Vruiser?

Ya gotta have a name for "Franky"! :D

Have fun..... and good luck! :)
.
 
Re: Mercruiser MPI conversion

I don't know what year all this cool fuel stuff started, but I have an 08 5.0 MPI with just the regular fuel/water seperating filter. and that is a good point about the shift interrupt switch.
 
The fuel injection is off of a Mag 350 with a Bravo drive so there is no shift interupt just a nuetral safty switch. Mercruiser puts the cool fuel pump after the raw water pump. I wonder if there would be a problem puting the fuel pump before the raw water pump. In the Seloc manual it shows a MPI system for a 5.7 with one fuel pump (in the cool fuel pump). It also shows another system with a low preasure booster pump before the high preasure pump. The later model Gen 3 cool fuel pump has both pumps built into one pump much like the volvo penta pump. I wonder if I should look for a Gen 3 pump set up. The other problem I have is I don't have a serial# from the donor engine. This make it hard to imposible to look up parts. I have a part number from the engine wire harness and I have part numbers from the ECM555. Is there a way to do a reverse lookup from these part numbers to put me into a serial number range?
 
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