mercruiser 2.5 / 3.0 rebuild help question ?

[larryb1963]

I have two 1980's mercruiser motors 2.5 and a 3.0 the 3.0 has the #1 cylinder worn and is seeping coolant thru the cylinder wall is this engine able to be sleeved ??? to standard specs .
The other motor 2.5 needs to be rebuilt. Is there any parts from my 3.0 that I would benefit from like the crank or the cam for the 2.5 is there any simple mods I can do to the 2.5 to get more HP from it ? Thank you .

 

[Alpheus]

Re: mercruiser 2.5 / 3.0 rebuild help question ?

#1 cylinder worn and is seeping coolant thru the cylinder wall is this engine able to be sleeved ???

Thats a new one. That is allot of wear to go completely through a cylinder wall.

Do you have any pics of this?

Are you sure its not cracked, or something punched a hole through it?

is there any simple mods I can do to the 2.5 to get more HP from it ?

Other than upgrading to a 3.0. No...

 

[larryb1963]

Re: mercruiser 2.5 / 3.0 rebuild help question ?

The motor is a salt water open system Im being told the 151 block is the 3.0 block bored to its max leaving the cylinder wall thin but is there enough to sleeve it ??

 

[Alpheus]

Re: mercruiser 2.5 / 3.0 rebuild help question ?

I personally am not a big fan of sleeving cylinders. I googled "mercruiser 3.0 cylinder sleeve" and it seems some people have had it done with success.

I would try ebay for a good block or look for a boat for parts. It seems every Bayliner I come across rotting in someones back yard has a 3.0 stuffed in it...

 

[coheej]

Re: mercruiser 2.5 / 3.0 rebuild help question ?

The problem with sleeving that block is that the other 3 cylinders are probably just as thin. Also when you bore it out for the sleeve because of its thinness, you will probably bore all of the cylinder wall away. You will only have sealing at the very top and bottom. I wouldn't try it.

Check to see what the casting # on the 2.5 is. If it's a 2770087, those were used on both the 2.5 and the 3.0. Have a machine shop sonic test the cylinder wall thickness. Many of them (maybe all) were cast the same even though some were bored for the 2.5 and others were bored for the 3.0.
I bored a 2.5 (3.875" bore) out to a 3.0 (4.000" bore). The cylinder wall thickness after boring was just as thick as the 3.0 was. Again this was casting #2770087. Most of the older 2.5's are too thin.