2004 merc 250xs

[Jiggumup]

What can you guys tell me about this motor? Looking for all the good/bad you can get me. Familiar with Merc EFI's as that is all i've ever ran.

I think I saw somewhere that this requires premium/91 octane...true? What happens if lower octane is used? Wouldn't plan on it but it is on a boat I am looking at and can't guarantee that its never had anything different

also heard you could run lower octane through if you put additives in it? any truth to that? And what additives would you have to add?


Thanks

[gambler1]

I've got that same motor. Min. 91 oct. has been a very good motor. only downside it has a 5850 rpm limiter. Butttt a Verrrry Strong motor that is great on fuel. I always run a min 91 oct I think the way motor is setup you could screw it up running less than 91. I think it's a timing issue

[John Jackson]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by gambler1 &raquo;</td></tr><tr><td class="quote">I've got that same motor. Min. 91 oct. has been a very good motor. only downside it has a 5850 rpm limiter. Butttt a Verrrry Strong motor that is great on fuel. I always run a min 91 oct I think the way motor is setup you could screw it up running less than 91. I think it's a timing issue </td></tr></table>

Ditto. That's what I run on my Stroker. LImiter is listed as 5850. In reality, alarm is 5850 and limiter 5950.
Makes it hard to prop on a fast boat.

[EuropeanAM]

Good engines. Above info is accurate... you MUST run 91 or higher octane. Anything less CAN result in POWERHEAD FAILURE.

This engine's PCM can be reprogrammed.... to achieve the same results as a 2005 250 XS (contact Eric Simon @ http://www.simonmotorsports.com for information).

[canadabullet]

I have the same 2004 250 xs on my 21 XDC Bullet and it has been perfect.... No issues with the motor at all , you must run 91 min. octane ... I have lots of hours on mine and I am not exactly timid with it ... The low rev limit does make it a bit hard to prop... There are two options that I know of to fix this ; you can retrofit the ECU from a 2005 model 250 xs with the high rev limit which is what I did , or, like Don says have your existing ECU reprogrammed ....