Replacement block for 3.0 from GM?

Scarebird

Scarebird

Cadet
Joined
Aug 31, 2007
Messages
12
First post here :p

I bought a 1988 17' Bluewater with 3.0 Alpha that was more of a fixer-upper than I thought. After repairing the ignition, installing a rebuilt starter, freeing the stuck trim cylinders and rebuilding the trim pump - I tossed on the muffs and ran it to set the carb. I was cheerfully greeted after 5 minutes by some chocolate milk coming out the valve cover (so much for taking my daughter out on Lake Washington this weekend :mad:). After checking this and other online forums, a sound guess would be the block is cracked. I will need to drain the oil/water out today and pressure check it later, but in the meantime does GM offer new bare blocks? If so,what part number?
 
180shabah

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: Replacement block for 3.0 from GM?

This is an industrial engine(construction equipment, generators etc..) so getting a block locally can sometimes be a challenge. Besides it is usually cheaper(in the long run) to purchase an assembled block(you will have to determine if you need long or short assy. For this there are many many options online. Rapid-O marine in Florida has proven popular with other members, as well as ebasic and jasper.
 
Flyin1500

Flyin1500

Petty Officer 3rd Class
Joined
May 31, 2007
Messages
83
Re: Replacement block for 3.0 from GM?

Ebay is a good start. I just typed in mercruiser 3.0 in the search function and there is at least one engine there (new). Google it too for other places for a new long block. Craigslist usually will have one or two used in the seattle area each week. Good luck!
 
R

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Replacement block for 3.0 from GM?

you can buy that engine new for about 1900 as a hot run long block. comes with the balancer and a delco EST ignition system.
add a new manifold and your lake ready for less than 2500 with a new engine/manifold. plus a year warrenty on it.
 
Scarebird

Scarebird

Cadet
Joined
Aug 31, 2007
Messages
12
Re: Replacement block for 3.0 from GM?

Good to hear there are more options than the 850 for a used OMC longblock at a local supply house :).

I still have a good OSCO manifold and riser for my old stringer OMC 250- inline six. Would it be too difficult using a 250 in place of the 3.0? Fabrication is no issue here- I build custom brake conversions for a livin'.
 
R

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Replacement block for 3.0 from GM?

to change from the inline four to the inline six may be more of a fabrication headace than its worth.
the outdrive gear ratios were a lot different.
plus the engines were not the same length making engine box modifications mandatory
its hard for me to rebuild a 3.0 for 1500 and I can buy a brand new long block assy for 1900 that comes with an ignition system and 1 year warrenty.
thats why I dont rebuild much anymore.
at 80 an hour for labor its just to cheap to buy new.
 
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