3.0L Mercruiser (GM) cross-reference

anesthes

Petty Officer 2nd Class
Joined
May 5, 2003
Messages
186
I just bought another boat. My first sterndrive.<br /><br />It has a Mercruiser 3.0/181 140hp alpha-1 setup. The guy who owned it had a head gasket problem, and rather than taking it to a mechanic attemped himself to destroy the motor.<br /><br />All the cyls are rusted now. Prolly froze. THe head he left _outside_ so the chambers are _ALL_ rusted. Valves do move, but it obviously needs work.<br /><br />Anyway. I spent the last two days trying to research this 3.0 block. Other than the fact that it is:<br /><br />181 Cid<br />9.25:1 compression<br />Uses 4.000 inch pistons (same as 350??)<br />Uses 1.94/1.60 valves (same as 350??)<br />Is 140hp in marine form, but only 88 in industrial<br />form.<br /><br />Since I can't seem to locate a local one used, at least for what I think is a resonable price for a long block (keep in mind I have everything else in perfect working order). I'm curious what automotive applications use the same basic "block". I know the cam is prolly different, and can re-use that but. There has to be SOME vehicles that use the same block/head design, even if the bore/stroke and valve sizes are somewhat different. <br /><br />What will bolt in? Get me through the summer anyway.?<br /><br />-- Joe
 

denniz

Senior Chief Petty Officer
Joined
Aug 21, 2002
Messages
743
Re: 3.0L Mercruiser (GM) cross-reference

I have a 96 model complete $1200. but im in Texas.ROAD TRIP!!!!!!
 

ODDD1

Lieutenant Junior Grade
Joined
Jan 23, 2001
Messages
1,054
Re: 3.0L Mercruiser (GM) cross-reference

Joe, there is no automotive equivalent. This motor is basically half of a 350 chev....industrial and marine use only...even if you do find a used one,there were many changes over the years, ie: 2 peice to one piece rear crank seal, with requisite crank change...a number of different cyl heads, differing comp numbers and different port/manifold hole sizes/locations....bite the bullet and buy a long block[by serial number] and you will have a shot at a reliable boating season.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,095
Re: 3.0L Mercruiser (GM) cross-reference

Take your's to a Machineshop,+ Have it rebuilt....<br />a .030 over-bore,+ 4 new pistons....<br />Then you'll be Boating......<br />I've got 3 in the garage in varying degrees of "ready to run".....
 

mlslocks

Seaman Apprentice
Joined
Mar 30, 2003
Messages
49
Re: 3.0L Mercruiser (GM) cross-reference

ODDD1<br />There are automotive equivalents. They are just old. 60? chevy II, early 70's GM products and Some mail jeeps came with the IRON DUKE block. This was the 2.5 liter engine. The 3.0 is a bored and stroked version of the 2.5, 120hp
 

anesthes

Petty Officer 2nd Class
Joined
May 5, 2003
Messages
186
Re: 3.0L Mercruiser (GM) cross-reference

I picked up a used one (1989) for 300.00 from a marine dealership. Its "as-is" but it runs, and may provide enough parts to make a "better than as-is" motor..<br /><br />Thanks for the responses.<br /><br />I'd love to get part #'s for the .030 pistons and rings. I can bore 'em to 4.030 in like an hour..<br />(I own a race shop). <br /><br />I guess I should dissasemble and see how close these pistons are in size, weight, etc to a sbc 4.00 piston. <br /><br />-- Joe
 

Bondo

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Staff member
Joined
Apr 17, 2002
Messages
71,095
Re: 3.0L Mercruiser (GM) cross-reference

NAPA lists Std., .020, + .030 over pistons for the 140hp,By serial #s.... Page 371, in catalog # MSP-7...
 

ODDD1

Lieutenant Junior Grade
Joined
Jan 23, 2001
Messages
1,054
Re: 3.0L Mercruiser (GM) cross-reference

yeah, the 2.5 /120 hp is the same as the old chev II motor....but is it the same as a 3.0? block the same? crank the same? head the same? just because it fits in the same space dont mean 'equivalent'...
 

mlslocks

Seaman Apprentice
Joined
Mar 30, 2003
Messages
49
Re: 3.0L Mercruiser (GM) cross-reference

as I stated bored and stroked 120/2.5. so stroked means different crank . Block is the same casting. Head may be different.
 
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