Hello,
I have two Mercruiser 377 Mag Mpi in my boat with imco Powerflow exhaust from 2015
Gived it opinium with little tuning this engine?

Can i change the rocker arms, from steel arm 1,5 to full rocker with 1,6 ratio? Will this work?
Or must i programming than my pcm?

Thanks
Patrick

It is essentially the same as going to slightly larger cam.
I don't think you will see any significant gains in power. Maybe 10-15 hp at most which equals about 1 mph.

Most likely you would need to have the ECM tuned. If you installed a wide band O2 sensor and guage, you could check the readings.

Do you have a PCM555 or MEFI ???

Okay, i have a pcm555

I'm pretty sure the only one who can even custom tune a PCM555 is Whipple. I would just leave the engines stock..

He will have ECM 555

PCM 555 was for the 496 Mercruiser Non Cat engines

Correct not worth doing anything to these stock 6.2 MPI and down MERC engines. one is longevity can be comprised and really sometimes no performance are gained either after all that time, effort and money.

I would play with props and take weight out of the boat if all possible. A very Clean bottom and clean water to the prop(s) plus a very straight skeg also helps as well.

Thanks to all. I Think the Stock Engines is than the best..