Black scorpion ecm modifications?
 

I have a 2007 tow sports 5.7 black scorpion. I bought it with the engine block cracked and put a 383 in it. Motor is in and running.
only mods were the cam (xm270hr) and the displacement.
Do I need to tune it, or will the computer make it run well enough? If I need to tune what's the best way to do that?

Don't see a motor serial number so I'll guess it has a 555 ECM. Merc tunes all motors fat and it may be ok but would need to get AFR readings to determine if a retune is needed. With out AFR readings or lots of plug analysis, then it needs to be retuned

The motor is from 07 so I'm pretty sure it's the 555.
I'm pretty sure it has 02 sensors and cats.
I hadn't thought of checking afr. What are mechanics on doing that? Imagine that I want to be able to have the O2 sensors working properly so I guess I'd have to drill another hole?

Accidental double post, sorry.

I'm looking up on BAM's site and last 350 MAG MPI had 555 but did not have CATs. CAT's came to Merc town in about 2010

If your motor does have CAT's then it has at least a PCM09

While reflashing a 555 is hard and not many can "actually" do it, no one can do a PCM09 that I've heard of

To measure AFR it requires as you say O2 probes installed in the exhaust and see what's going on with AFR meters

New ECM is $2300

Whipple can do both.....

I would get current real time wide band readings and see what your existing AFRs are doing. If within limits run it. If not then get it tuned as mentioned above.

They say they can, but talk is cheap

I called Whipple a couple of years ago and they told me they could reprogram PCM 0905. But I would have to run 91 octane and I didn't go through with it.
NOW YOU'RE SAYING THEY LIE TO ME? Do you work there? I'm curious to know how you know their talk is cheap.

Nothing of the kind, you believe them I don't. Prime example, would have to run 91 octane easiest way to do nothing when reprogram is required, say use higher octane fuel so if it runs lean there will be less chance of damage. A Merc 383 only needs 87

Another thing is Only whipple can do it, if it was do-able others would also

You may be correct and they are the only ones that can do it, I just don't believe it

I didn't know that I had to explain myself when I said Whipple could program the CAT. PCM. Normally I wouldn't explain myself to you AllDodge. I do so for Chrisut so he doesn't get the wrong idea.
The reason why I mentioned 91 octane is because I wanted them to do a whole remapping of my PCM-0905 for top performance. Instead of the laid-back original mapping from MerCruiser. I decided not to do it.
Whipple has been in business for roughly 43 years. Annual sales about $5 Million. Their products are on top fuel funny cars and dragsters to the common car. You don't get that way, that far, by lying to people. THE END.

What engine platform with PCM-0905 were you asking them about having re-tuned? Heres something else to consider:, if they have re-tuned a BIGGER engine with that PCM BUT dont have a DEVELOPED tune for the OP's engine, its possible they still might not be able to help him, the answer will be a simple phone call though to see, Smitty

Anybody know for sure? They have basically stopped everybody from tuning ECU's for outboards. Arent these governed the same way? Isnt tuning kinda gone now for all merc platforms or only outboard?

I don't for sure as never needed it.
FWIW
But I remember awhile ago there was a thread on here where the poster said he called Whipple and HE claimed Whipple told him they received a cease and desist
from Mercury regarding tuning the catalyst engines and told him they wouldn't tune his.

sorry to resurrect this, but I’m in the exact same situation. What did you end up doing, and how did it work out?

I havent done anything yet. I've been too busy and this one has been on the back burner.

well since that’s the case here’s what I found out today.
I called a bunch of performance boat shops. Seems like the common answer is that is “should” be fine as long as the cam profiles are similar.

The issue I’ve now run into is that after calling mercruiser… they don’t know/won’t tell me the cam specs because the guy claimed they are all made in-house and won’t give out that information…. He then referenced me to part number ( 8M0187372 ) which is the new 383 replacement engine they sell…. I’ll save you some time.. it’s $11,000…… so I called the guys over at ATK high performance and they sell a 383 that’s a direct replacement for our engine (it’s the HP105)… it’s still $6200.. but that’s a hell of a lot better than $11k