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Mercruiser 5.7L Roller VS Flat Lifters ECM Diff?

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fd0110

New member
Hi, Desperately need some advice.
Old engine is flat lifters, bought a new one with Roller Lifters. Doing research online I see that there's two different ECM's that year 96/97. Each ECM for either Roller or Flat Lifter type. Do I need to buy a new ECM now? I'm sure there's a difference since they have one for each but, what happens if I just keep the one I have? Don't want to take chances with my new engine but a new ECM is $1,600.00
Boat is a 96 Sea Ray 215 Express Cruiser, Engine is a 96 (although by the serial number comes up as a 97) Serial number is K007163. It has EFI/TBI 2 bbl.
 
I just checked this site's parts pages for a '96 350. The various ECM's are tied to the out drive type (alpha or bravo) engine model (lx, magnum, etc.) or the combination of the two. Lifters don't enter into it, unless they're tied to LX, Magnum, etc. The two lifters are also shown here, but no model differentiation called out.

My air-grab would say run it with the controller you have. Since the engine is EFI with a knock sensor & module (right?), I don't think you can hurt it. The Thunderbolt V timing advance curve adds up to 15 degrees over the non-EFI Thunderbolt IV's curve (up to 37 deg. BTDC), and the knock sensor and module keep it from blowing its head(s) off. If you have a Thunderbolt IV on an EFI, I think you will be even more safe, 'cause the max advance is only 22 deg BTDC. Very safe, but maybe a little less acceleration performance and cruising fuel economy.

http://www.marineengine.com/parts/m...9999/wiring-harness-and-electrical-components
 
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Please note:
Ignition advance degrees are absolutely meaningless without an associated RPM.

As for Roller cam followers -vs- flat tappet cam followers, I see little to no difference if the profile is extremely similar.



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fd0110 said:
Hi, Desperately need some advice.
Old engine is flat lifters, bought a new one with Roller Lifters. Doing research online I see that there's two different ECM's that year 96/97. Each ECM for either Roller or Flat Lifter type. Do I need to buy a new ECM now? I'm sure there's a difference since they have one for each but, what happens if I just keep the one I have? Don't want to take chances with my new engine but a new ECM is $1,600.00
Boat is a 96 Sea Ray 215 Express Cruiser, Engine is a 96 (although by the serial number comes up as a 97) Serial number is K007163. It has EFI/TBI 2 bbl.
Click to expand...



Ok, UPDATE!

I had the flat tap type but following my mechanic's recommendation I purchased a roller type. Then doing some research I found a site with parts list for my engine which lists two different ECM for either the Roller or Flat tap lifters. I freaked out and started this thread looking for advice, and thanks so much for all who replied
.
The next day I drove to the marina to look at my ECM and it turns out that I do have the one listed for roller type engine although I had a Flat type. Go figure, I guess it doesn't make much difference anyways or perhaps it was replaced by a previous owner. I'm also told on those years 96'/97' Mercruiser was going through a lot of changes and did some odd things.

Again, thanks to all for the help!!!
I can't wait for next week to get my boat in the water and enjoy the rest of our short season.
happy boating everyone,

site where I found the details.
http://www.marineengine.com/parts/mercury_marine_parts/sn/0K007163/457B101KS/2338_60
 
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