350 mpi rebuild questions

[vroom ZOOM]

Well, I tried communicating to the cooked ECM through K-TAG, but no luck, I think its really toasted. I guess I will keep it around for spare parts. On the positive side, I bought a whole box of 350 mpi ECMs with some good ones to use and some bad ones to tinker with. When digging through them, I realized another fact. That is, they are not all the same.

So it turns out that 2002-2004 ECMs use only two injector drivers that fire four injectors each. They also run only one knock sensor. Some 2004 and up use four injector drivers and two knock sensors. The ECM and wire harness on these two versions is different. So it seems like the harness that survived in my boat is the older type and the ECMs I have are the newer type, so I will have to either trade it for a newer type harness or modify the old one with a couple of wires to the injectors and knock sensors.

On a positive note, I finally got the longblock put together. Its still missing the core plugs and the heads haven't been torqued down yet, but its getting there. As per recommendation from my machine shop, I bit the bullet and installed stellite exhaust valves.

Also the machine shop guy said not to bother getting marine head gaskets, as apparently he called manufacturers and they couldn't tell him what the difference was between the regular and marine versions. I am kind of on the fence about this, but to check this theory I will take a new blue stripe gasket and one from the "mercruiser built" motors and soak them with all sorts of stuff to see if they rust at the same rate. Then I will know! Anyways, here are some pics of the first motor going together, pls ignore the organized mess:

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[Scott Danforth]

Marine MLS head gaskets are stainless, including the fire ring
Automotive have mild steel

 

[Scott06]

Marine MLS head gaskets are stainless, including the fire ring
Automotive have mild steel

Exactly while many on here have said they used automotive gaskets successfully not sure why you would screw around over $100 cost diff being this deep into it.

 

[Scott Danforth]

Last I checked, the difference in cost was only $6. the felpro head gasket set is $130, the felpro marine head gasket set is $136

 

[Scott06]

Last I checked, the difference in cost was only $6. the felpro head gasket set is $130, the felpro marine head gasket set is $136

Ok eve more so I just pulled a number out of my azzzz

 

[vroom ZOOM]

Well, you internet warriors have convinced me to grab that stainless head gaskets. Got the marine 17030 felpro gaskets for 29 bucks each, so not too bad. Non marine were 15 bucks but its not too bad of a price diff. Picked up new crab caps and belts while I was at it. Hopefully I can get the motor finished by the end of next week.

Meanwhile I was busy cleaning up all the accessory brackets, motor mounts etc. Current method is to get them hot with a big blowtorch to burn the grease off and flaking paint, and then hit them with the sandblaster loaded with steel shot. Problem is, this takes a while. I tried to construct a vibrating tumbler loaded with crushed glass but it didnt do squat. Maybe a rotating one is better, or I need different media?

 

[Scott06]

Well, you internet warriors have convinced me to grab that stainless head gaskets. Got the marine 17030 felpro gaskets for 29 bucks each, so not too bad. Non marine were 15 bucks but its not too bad of a price diff. Picked up new crab caps and belts while I was at it. Hopefully I can get the motor finished by the end of next week.

Meanwhile I was busy cleaning up all the accessory brackets, motor mounts etc. Current method is to get them hot with a big blowtorch to burn the grease off and flaking paint, and then hit them with the sandblaster loaded with steel shot. Problem is, this takes a while. I tried to construct a vibrating tumbler loaded with crushed glass but it didnt do squat. Maybe a rotating one is better, or I need different media?

Never used steel shot in the blaster always used white play sand. If you are going to last the just blast with sand. Wire wheel on grinder works well too does make as much mess as blasting

 

[Scott Danforth]

Degrease in heated solution of simple green and water. Let sit for a day. Hit with electric pressure washer. Then toss in oxalic acid bath for 2 days. Hit with electric pressure washer. Dry off, prime and paint

 

[vroom ZOOM]

Never used steel shot in the blaster always used white play sand. If you are going to last the just blast with sand. Wire wheel on grinder works well too does make as much mess as blasting

gotta be careful as play sand will create nasty silica dust in the blasting cabinet. Usually I use crushed glass that is specially made for blasting and doesn't create silica dust.

 

[vroom ZOOM]

Anyways, one down. Still a couple of hoses left to connect when I get the manifolds, but the motor is otherwise complete. Now for the second motor!View attachment DSC_0783.JPG