Mercruiser 3.0 rebuild & outdrive help!!

[viper122]

I recently bought an 18' Larson bowrider project boat and I'm needing some advice from the expirenced out there. I am very familiar with car engines but I also understand that there are major differences between marine and auto engines.

I have a 3.0 mercruiser serial 0L319125 with a mercruiser 120 outdrive. The guy I bought it from left it sitting out in the rain for years and it had a bunch of water in the pan and manifold. I removed the cylinder head and the pistons and walls are rusted pretty bad.

Now my questions... Is this worth stripping down to the block for a rebuild, or just finding a used or rebuilt engine? I want to go with whatever is more cost effective yet reliable. Also, if I decide to shop Around for an engine, what specs and engine size should I be looking for as far as being compatiblE with the mercruise 120 outdrive?

I'm sure these are pretty amateur questions but any advice is greatly appreciated!!!

 

[Don S]

Re: Mercruiser 3.0 rebuild & outdrive help!!

The biggest problem would be if he allowed the boat to set with water in the cooling system where it could freeze and crack the block.

 

[Bondo]

Re: Mercruiser 3.0 rebuild & outdrive help!!

Is this worth stripping down to the block for a rebuild, or just finding a used or rebuilt engine? I want to go with whatever is more cost effective yet reliable. Also, if I decide to shop Around for an engine, what specs and engine size should I be looking for

Ayuh,... If it's rebuildable,... Rebuild it...

If it Ain't,... Find another, Just like that 1...

 

[viper122]

Re: Mercruiser 3.0 rebuild & outdrive help!!

I equally have the same concern, what is it that I would need to look for in a used mercruiser to assure it fits my mercruiser 120 outdrive?

 

[viper122]

Re: Mercruiser 3.0 rebuild & outdrive help!!

Also has anyone been in a similar issue that can give me a ballpark figure on the cost of a rebuild vs. Purchasing a used or rebuilt motor?

 

[elkhunter338]

Re: Mercruiser 3.0 rebuild & outdrive help!!

A new 3.0 is $3000 from michigan motorz. I was going to have to have sleeves installed in my old block at $100 a sleeve. I seemed it was not much more $500ish to go brand new.
If you have a good block then call a place near you that rebuild boat engines and get a quote.
Has your old block already been bored out, if so with the rusty I personally would not get is bored .060 because of thin cylinder walls. My old engine block was bored .030 and it looked like it had a pin hole starting in the #4 cylinder when I tore it down. The reason I tore it down to rebuild was because it broke the timing gear.

 

[fishrdan]

Re: Mercruiser 3.0 rebuild & outdrive help!!

Remove the manifold and check to see if the block cracked behind the manifold, they usually crack there. Also look for pushed freeze plugs, or other cracks (rusty lines). If it passes the visual check, have the shop magnaflux the block before performing any machine work. Also check the manifold, they can crack from freeze damage too. I'd completely disassemble the engine, and take it into the machine shop to get their opinion of the work needed to properly rebuild the engine.

I completely rebuilt my 140HP (basically the same as a 3.0L) 3-4 years ago and it was right at $900 for the long block, $450 for parts and $450 for machine work. I did all the assembly work, but I think they said it was only another $200 for them to assemble the engine. The manifold/elbow was pretty new so I didn't replace it, that would have been another $300+-. I also replaced the fuel pump, alternator, water pump, starter, hoses, this, that..... I was easily $1500 into it, but everything was rebuilt or new.

BEFORE doing anything to the engine, have the drive checked and make sure it's OK. You don't want to rebuild the engine, only to find out you have a bad drive. Better check to see if the deck, transom and stringers are good too, before investing a bunch of money into the engine.