I'm trying to make some minor cheap upgrades to my 2007 Chap 256ssx.

It currently has ECM# 3885461, which is correct for the 380hp 8.1, Gi-H package.

I managed to find a complete wiring harness and ECM from a VP 8.1 GXi which is supposed to be a 420hp combo and compatible with Raylar kits. This ECM is number 3883664 and I *believe* is from 2005.
I also have a few new 420hp HO camshafts under my workbench... so that is a cheap option as well.


I'm curious what issues I may encounter and if this 3883664 ECM will plug into my existing 2007 harness, or if I will need to swap the entire mess. I dont know what years the 3883664 ECM was used and if it's compatible with my 2007 drive by wire throttle. I have no problem swapping to a cable throttle if thats the only issue... but it would be eff'n wonderful if it would just plug and play.

I spent $500 for this used harness and ECM so I dont want to just jam connectors together and brick the ECM.

Thanks in advance !

Reach out to John Mosetti (BUP) at Boats Unlimited - he's in the Houston area. He's really good with the factory ECM thing. Not sure about Volvo specific, but I know that he is able to repair the GM ECM at the board level. Worth a shot.
https://www.boatunlimited.com/

What exactly are you trying to achieve??

Sounds like he's turning a 8.1 GI into a 8.1 GXi with a cam and ECM change.

Be warned that GXi ECM tune is one of the worst running and bad behavior inducing software programs ever. I don't know what they were thinking when they programed it. During the time they were for sale, the dealer I worked with actually wouldn't order the GXi's because they were just awful and the Gi's were fine.

Another reason the Merc 496's were better IMHO. Smooth......

Where you been Griff?

I just cant leave anything alone !!!

PSI 8.8 liter / 550ci ???

Mo powa

Whats Larrys take on this? I know Ray wasnt big on them at all... I know its money, but its money well spent. In a HP application, like what you are going after I dont know if its worth messing with the volvo ECU.

Per email from Larry Hofer, the GXi ECM works well with his 525 and 600hp kits.

I do have a local guy that swears he can hack the ECM... but I havent connected with him yet on this.

I'd like to try running one of these 8.8's on a test stand using the VP ECM if possible... just to experiment and play around with tune/software before it gets anywhere near the boat.

Problem is, much of this depends on this garage im trying to build and it's already a month behind schedule.
I cut a check for $44,500 back in December and all I have to show for it is a big hole in the yard. I may own a Kubota skidloader too if they dont soon get back out here for it.

Just sent him a message.

Thanks!

Im trying to keep it simple and avoid running aftermarket engine management if possible...

Larry Hofer says the GXi ECM is the way to go with his 525/600hp kits... so I assumed it wasnt too horribly bad.