Mercruiser 3.0 LX Cracked Water Jacket

[kschnebly]

Hello All,

I am in the process of purchasing a 91 Webbcraft Falcon. This has a 3.0 LX Mercruiser. As I was going through the motor I noticed that there was a crack in the block beneath the intake manifold. The boat was not properly winterized last season and I am sure it froze. I have rebuilt the carb, put in a new battery, changed the plugs, and changed the oil. I finally got it out on the water today and ran it under load for about 2 hours. I checked the oil and there is no signs of water and the level stayed the same. My question is, "was 2 hours on the water sufficient to determine if the crack is just external?" I still have a chance to back out of the deal but since I already have money tied up in it and the boat is really priced low I would like to keep it. Any advice would be great. Thanks,

 

[Levithan]

Re: Mercruiser 3.0 LX Cracked Water Jacket

If you have no water in the oil, temp was good and there is no water in the bilge it could just be a casting flaw.
2 hrs is plenty sufficient to notice water in the oil or bilge.
There are many threads on how quickly a cracked block/head mixes or leaks fluid, usually very quickly.
Hope that helps.

 

[achris]

Re: Mercruiser 3.0 LX Cracked Water Jacket

If nothing showed in 2 hours, you're probably good to go. Even if it shows something down the track, there are plenty of 3 litre engines in rubbish boats that you can pick up for next to nothing and do the 'donor engine' thing....

 

[tinkerguy70]

Re: Mercruiser 3.0 LX Cracked Water Jacket

From everything I have read, and from my own cracked 3.0 experience, they all seem to crack in the same place. Directly under the intake manifold toward the front of the block.
Mine was cracked about 8 inches long.
One sure fire way to know if it's cracked into the oil is to pressure test the block. It's not very hard to do and I believe that information is in one of the stickies on the top of the page.
After pressure testing mine (to make sure I wasn't wasting my time), I used a grinder with a wire wheel and cleaned the crack out really well, then put JB weld on it in 2 applications, 1 the first day and the 2nd coat the next. It seems to be holding up just fine so far.
The only downside is you have to pull the intake manifold to get to it.
Anyway, I'd say you are OK too after running a couple hours with no water showing up in the crankcase. The only real reason I even fixed mine was to stop it from leaking into the bilge. It was a small leak, nothing to get excited about, but a leak all the same.

Hope this has helped and good luck!

 

[achris]

Re: Mercruiser 3.0 LX Cracked Water Jacket

And drill a small (1/16") hole at the ends of the crack to stop it progressing...