Can the merc 250 v8 be remapped to a 300?
 

I think I read all the internals are the same that only the mapping was different between the two engines. Thanks in advance for any info, RM

Not legally.

Was it legal to remap the verado inline 6 engines? I saw numerous threads on remapping those. Thanks

What law is that??

For warranty sure , but not sure if a legal thing. Emissions maybe ? Are the emission police that bad ?

i want to do it after my 1,000 hour warranty expires which should be in 230-240 days from purchase.
who is offering this service? Thanks

Wish I knew. But none of the shops who used to be willing to flash Verados are willing to do it anymore. Mercury and the EPA have aggressively shut it all down and their effort seems to have been effective.

As noted above...very few mainstream shops will do anything like this now. Look what happened to Diesel Brothers, for example, in the truck world.
Many, many, years ago (think mid/late 70's) when cars were starting to be equipped with catalytic converters, there was a local shop that would install "test tubes" that replaced the cats for...you know...'testing' purposes. Guy made a name for himself until one day he gets busted, all assets (including his home) seized, fines and jail time ensued.
Point being, the risk outweighs the reward and especially these days, the government agents hang out on forums just like this, waiting to snare some poor bastard.

As for CAN it be done, i.e. make the tune deliver the ponies...I don't know, but if it's simply a matter of altering injector duty cycles and timing, etc...then it seem logical it COULD be done. If it HAS been done, and one can get one's hands on the tuning equipment, and do it himself...one would be golden, and unlikely to ever get caught in some random check...as long as that person was smart enough to NEVER say anything about it publicly.

Taking a 1,000 hour engine and increasing its power by 20% would surely put more stress on everything. I reckon you’d considerably shorten the remaining lifespan of many components. They don’t get stronger after 1,000 hours of use. 🙂

Could it be done….? Probably, but in commercial use, I think you’d regret it down the track.

RR

I thought both were NA, seems like a lot of HP out of just a tune.

From what I have ready the engines themselves are identical insofar as the powerhead is concerned...so yeah, Merc must be doing some 'black magic' on a normally aspirated engine to get 50 more ponies...either that or they radically DE-tune the 250 hp version.

One only needs to look at the MAX RPM Limits of the 250R vs the 300R to see how the "Black Magic" is done to make 50 more HP. I am certainly no expert on this, but it seems like that it how it is done.

Hmmm...I must be missing something? Because all the specs look to be exactly the same. From the Mercury website:

https://cimg1.ibsrv.net/gimg/www.off...5355db4a6a.png

I was looking at the "R" motors specs, they have different max rpms, for a 250R vs 300R, not the regular V8 motors. Sorry about that.

That is strange that they have same everything but HP rating.

Yeah...so it kind of implies that perhaps the 250 is a detuned 300? But how, exactly?

The PRO XS all rev to 6,200, the 250 Pro XS is the same as the 250R power wise (270 ish HP). The 300R has different cams, intake, ecu; makes significantly more than 300 HP. The regular four strokes have different exhaust and tuning. They may have different intakes but I don't know for sure.

The HP difference between a 250 ProXS and 300 ProXS is small, not worth messing with.

the 225 to 300 are all the same engine with the exception that the 225 has a smaller diameter airhorn on the intake to reduce power. The 300r has a lot of different parts. The 250 and 300!are identical. It’s 4.6 liter v8. So it’s a very mild state of tune @ 250hp. Hell most 1 liter sport bikes make 200 ponies lol

it’s a 4.6 liter v8. Only 250hp is weak af for that large an engine.

I’m in South America so I hope for export a remap is available

I know a lot of the smaller engines are identical except for restricting air flow.

I had a Yamaha 9.9 that I made into a 15 with just bending the Reed cage to let the reeds open more. After that instant 5hp.

Just bought a 20hp mercury 4 stroke. Both the 15 and 20 are the same except for air restrictor (washer) installed in air tract to restrict flow and a different programed ecu (efi). They charge quite a bit more for the 20 than the 15, but the cost of a new ecu was double what buying a new 20hp ecu was.

This is very common with out boards.

I could list a lot of engines which are just about identical with different hp ratings.

I don't know much about the engines you are asking about. I would post over on the hull truth. A lot of outboard guys there. I'm sure someone could give you the answer.

The real data is in the emissions reporting info. I remember seeing as high as 316hp, must have been the R.

I suspect the I6 may be on the way out and they go up to 350hp NA.

Yes, I agree, it’s pretty tame hp from 4.6 liter. On the up side, it may be more durable than its higher output brother……. (Lazy engine, nothing’s stressed, longer life)
Only guesswork, I’m not a mechanic. 🙂

RR