I’ll save the sob story on how I got here, but… can you have a 555 ECU tune changed from a 496 MAG to a 496 HO?
Engine is an HO and I’m pretty confident the tune is a MAG. Previous owner had the long block replaced before I bought it. Rough idle, wants to stall out and a little miss under power.

From reading, seems Mercruiser is very much against tuning, but what about a base factory tune?

Thank you

Whipple Mercury 496 Magnum Stage 1 and 2 (whipplesuperchargers.com)

540,

I'd think Merc would reflash it to factory, wouldn't they? I don't know which would be cheaper. I can tell you that Whipple's stage 2 tune was $800 in 2021. I'm not sure what it is today, if otherwise. Website only give pricing for stage 1 at $695. I'm also pretty sure Whipple's "stage" tunings are upgraded tunings, not factory, even though stage 1 is only optimization for 89 octane fuel. Not that that would be bad thing....

Have you put it on a Rinda?

Thanks. Brad.

Whipple tune also cleans up the transom suit and tunes the motor from being so fat in the fuel curve. It will be an overall win if you choose that route. A little better fuel economy and pick up 1 or 2 MPH overall. GOOD LUCK

CigRocket,

Not to derail....

One of two things is true... Either there's still something wonky going on with our 496HO/M1 ProCharger/Whipple Stage 2, or that "cleaning up of the transom soot" thing is a myth. We go through about two bottles of Greased Lightening every season cleaning our transom after a day on the water, whether we run hard during the day or not. It is sometimes worse than others, but doesn't seem dependent on anything I've been able to narrow it down to.

Carry on....

Thanks. Brad.

Mercury had a recall to refresh the 496 ecu to clean up the tune. Mine had the recall done and did not get soot on the transome.

Going on Rinda this morning and really hoping this is the issue. They seem to be out of ideas short of really tearing into it.

A tune would be an easy fix. But, I’m never that lucky 😂

540Fever,

Read this.....

Since this could go one of two ways....

If you have the ECM sent out (wherever), I would have a look at the injectors while you're down.

If you find the ECM is up to par, have a look at the injectors. You don't have to tear too far into it to get to them.

Either way, you have cheap insurance that the injectors won't be a problem moving forward. Get ahold of Smitty (ArcticFriends).

Thanks. Brad.