Um.....yes! One of the best investments I have made to date.

I agree with every thing MikeScarab28 has stated, plus I would add the support from Bob is simply amazing. He was on the phone with me for an hour on a Saturday morning.

The software is easy to use, uploads fast IMO.

I got my AFRs in check for idle and no boost cruising, 13 at idle mid 12s cruising. I am still rich under boost running high 10s (stock). I know she has more, but time is a factor. Really should get my cruising in the high 12s and boost up in the 11s.

After playing with the cold start enrichment I simply wiped it out.....yep, wiped out! Starts perfect, runs great and doesn't turn the transom black or load up as it did stock. It still amazes me how rich this tune was from merc, dangerously rich IMO

I lost my o2 sensor last year leaving it in the boat in the water, maybe moisture. I never touched the tuning since that, but I am ready to go again. Waiting for slightly warmer temps to start

Quick ?....Was your Mefi3 locked? If it was does the software unlock it?

My MEFi3 was stock and locked with the merc code, MEFIburn provided the code to unlock. He also has the stock files if your ecm has been modified and locked with a unique code from the tuner. Basically just wipe it and start from stock as the only option if the tuner has locked the ecm.

By quick I meant uploads took seconds after files were modified. You can not write live unlike some aftermarket systems. Fastest tune would be a system that referenced an 02 and makes adjustments on the fly, like what haxby was recommending.

I had a stock tune to work from, the engines have been modified but not re-engineered completely. If I was building from scratch, or after huge power I would have went with a system like haxby suggested.

Great info 4bus...I changed the blowers out to Dyers 8-71's. Everything else is stock. I went up to 32 pitch props and hitting the ref limiter. I want to change the rev limit and also I want to use 120 degree thermostats. I will give Bob a call this morning and order. Thanks for all the useful info. Next winter I plan to change cam's to roller like yours and I might be getting with you as how you like your setup.

I think you are safe to spin those stock cams up to 5500 rpm and still make power. How old are your valve springs?

You have may have to change the bpw vs ect enrichment table slightly with the colder stats, I had to lean mine out a little. At 130 ect my afrs were in the low 11s no boost.

Can't say enough about the full roller conversion and upgraded cams, peace of mind full roller, and more air in/out is always a good thing. The stock merc cam is very conservative The sound at idle is noticeably more healthy next to a stock 575sci.

Talked to Bob this morning and ordered. Let the fun begin......

Get some o2 bungs welded in the exhaust, and buy a good wide band afr.

Ive been lurking on this thread 4bus and decided to buy MEFIburn a few weeks ago.I have an interesting project a 1968 vdrive flatbottom with a Mercruiser 7.4 MPI MEFI3. Bob helped me out unlocking it as well i was suprised to see only 13-15 degrees of timing at WOT and i hooked my LC1 wideband up was playing around in the driveway with water hooked up no water going through headers my AFR at startup was 17:1 for a good 20 sec before it trimmed down to 14:1 or so Did you zero out the cold choke tables??

I am testing out new version of Datamaster for MEFI3 pm me if you wanna check it out.

Does the software tell you what optimal setting are for each table? If not where can I find the info to educate myself?

I have 2 poker runs in June and after that I will send my tails to CMI to weld in the bings. On second thoughts I'll call them this morning to see what their turn around time frame is. 4bus where did you weld your bings at?