Mercury 2.5 liter interchangeability

[Bgbbgb246]

Ive seen variations of this question asked but i cant seem to find a concrete answer. My question pertains to the interchangeability of 2.5 litre mercs from the late 90s and early 2000s. Specifically my scenario is that i have an xr6 150 with a blown powerhead. I havnt had a lot of luck in the used outbord market lately but i just recently found a nice complete 2001 150 efi for a good price. The problem is that the shaft length is 25” and i meed a 20” motor.

Can this powehead go on my midsection and lower end? If so, do i need to buy any parts? (Ive seen an adapter plate mentioned in some forums). Is there anything i should be worried about with this type of project?

 

[Dukedog]

get yaself a new power head gasket (for either one, xr6 or efi) and get after it.....

justa a reminder.. be sure ta disconnect (one 7/16's nut) the "sliding" part of tha shift linkage at tha anchor bracket before ya pull tha ph!..

 

[Bgbbgb246]

So it sounds like no adapter plate is needed. If its the same exact gasket then i suppose all of the ports are the same size and shape. Is it safe to say, just for my own knowledge, that all 2.5 motors and midsections are interchangeable or is this not necessarily true?

I will also need to to buy a lower unit because the one that was on my xr6 was “borrowed” and never returned. I found one locally for $500 that looks nice. Its from a 1982 mercury 200 which i believe is a 2.4 motor. Are 2.4 and 2.5 lowers compatible as well?

 

[Dukedog]

justa 'bout all 2.0, 2.4, 2.5 are interchangeable with a few things that need ta be done in some instances.. knowing what comes witha lotta experience 'cause there isn't any thing published ta tell ya what goes with what...

that gear case is ok for a spare but its whats called a "pre-load case".. its tha weakest of tha v6 cases... 'bout same as tha small dia XR4/6 as for strength.. don't remember for sure when tha pre-load went away.. maybe '87? anything after that will suffice.. don't know what props ,props ya have but gear ratio's can be different.. small dia XR4/6 will be 1.78 ta one.. standard size will be either 1.87 or 2 ta one's....

 

[Bgbbgb246]

Alright that makes sense. I guess i should specify. The guy thats selling this lower unit bought it for his 82 merc but the motor “lost cylinder 2” about 2 weeks after installing so he decided to sell the lower unit that he just bought. Ill attach the picture of the listing. Ive heard that whether it has 4 or 6 water pickup holes means something? Ive also heard that the numbers stamped on the lower unit dont provide much helpful information. Can you tell whether this is a pre load case from a picture?

 

[Dukedog]

can't tell from that angle.. pre-load has a "pin" stickin' outta tha top of tha driveshaft.. can't see either slots or anode right above tha cav plate either.. 4 hole inlet is on small dia. XR4/6 case only..

 

[Bgbbgb246]

well, i dont see a pin in the top of the drive shaft so it seems like its not a pre load

 

[Dukedog]

yeah.. thats a lot later model.. '95 or better.. think '94 and older had exhaust slots where that one has anodes....