300 powerhead on 250 mid?

[rstanley]

What is needed to do a complete swap from a 250xs to a 300xs? I’m guessing adapter plate, but any help would be appreciated.

thanks Robbie

[EuropeanAM]

Please review the Forum Announcements and Required Info. Thanks!

If we're talking "fully dressed" powerhead (with fuel system, electronics, PCM, etc), you would need:

-Adapter Plate

-Exhaust Tuner

-Gaskets, Clamps

Of course, doing so is technically illegal.

[tlt20xd]

Why is that illegal. Coast guard didn't say anything to me about a 225 pxs swap to a 300 xs. But they did write down the 300 serial # from the block. Just wondering!

[JOE54]

check emission ratings

[tlt20xd]

I don't. By the emissions thing. If the 300 was changed fully dressed and the exhaust can was changed. The 300 had pass emissions as manufactured it is just on a different center clam bracket. Name plate serial number would be my guess.

[Savage]

The clamp bracket has the serial number for a 250HP, so you motor is a 250HP.....You install a 300HP powerhead, and have thus changed the emissions for the 250HP, which is illegal.

[tlt20xd]

Sorry for jacking the post and I'm not trying to argue but up until just a couple years ago you could by a whole power head from and have installed by mercury authorized dealer. With emissions standards changing every few years how did they do powerhead replacements on motors that were a few years old. You can change motors in cars and as long as the pass emissions test for the new style and are factory with out upgrades it's legal. Even in California. So a 300 as manufactured that passed as is and that is not being hidden under a 250 cowel is still illegal. Don't make sense but I'm no lawyer.

[EuropeanAM]

According to the EPA, any change to the HP or Emissions footprint (outside of it's original disclosures) is a violation, with some potentially hefty fines.

That's the simple legality of it. When someone asks the question, they will get this as part of the answer.

[tlt20xd]

Government at it's best. Guess I'll let it lay.

[lpugh]

According to the EPA, any change to the HP or Emissions footprint (outside of it's original disclosures) is a violation, with some potentially hefty fines.

That's the simple legality of it. When someone asks the question, they will get this as part of the answer.

I do not know about marine, but I do know about autos. Regulations do state (If it was offered from the manufacture in that configuration it is permissible to replace it). That is California's interpretation, keep in mind even the feds are less stringent than Ca is.
I know the state requirements very well and used Instruct classes in preparing Techs for their Test and Repair Smog license. It may be a different deal with outboards since the boat and motor manufactures are not the same.

Here is some thing else to think about, in some cases for various reason we will fail vehicles with oversize tires! They will effect the emissions due to a different load being applied to the motor than designed just as the incorrect prop will to an outboard.

I am all for clean air, but this getting way out of hand

[rstanley]

Thanks for the input guys. I decided to go a different direction anyway but was intrigued with mercury offering the dressed powerheads. Just waiting on the 250R to come in now!