Mercrusier 3.0 litre block crack questions

[Wet dreamz]

I have read in several posts about attempts to repair a cracked block - my own stupidity allowed this to happen but I am hoping to repair a crack in the block of my motor (outside only - oil is clean of water) - I have read several posts in regards to the pinning (?) by drilling a hole at each end of the crack as well as grinding out of the crack before attempting to fill with JB weld.

my questions are:
1 How deep do I drill the holes at each end

2 What size drill bit do you suggest?

3 How deep do I clean the crack - do I clean it all the way in?

4 Should I apply the JB weld in layers? if so how many and how long do I allow to dry between applying layers.

5 Has anyone done this and been successful or am I wasting my time?

Thanks for any help - hoping to be back on the water soon

 

[Howard Sterndrive]

Re: Mercrusier 3.0 litre block crack questions

(outside only - oil is clean of water)

you know this from running it?
If you just pulled the dipstick....well, hate to break it to you....
the water will be under the oil...
If it wasn't winterized at all... there's very little chance the cracks are only external


OK...
assuming you have run it, or removed the pan plug to verify no water:

1 How deep do I drill the holes at each end

right through

2 What size drill bit do you suggest?

3/32" or 1/8"

3 How deep do I clean the crack - do I clean it all the way in?

doesn't have to be all the way in.... 1/8" fine

4 Should I apply the JB weld in layers? if so how many and how long do I allow to dry between applying layers.

I would just do one coat - but mix the JB with fiberglass strands - can get the f/g cloth at canadian tire up there.

5 Has anyone done this and been successful or am I wasting my time?

I have fixed an externally cracked 3.0 this way.
I have failed once.
Then I redid it with the fiberglass strands and it never leaked again.

But, if you haven't removed the engine drain plug or had the engine running ...then yes you would be wasting your time to start repairing it before removing the plug

 

[tmh]

Re: Mercrusier 3.0 litre block crack questions

Many have been successful fixing an external crack with JB Weld. However, it depends what you're dealing with. can you describe the cracks better?

I had read extensively on his a while ago but my block and manifolds were cracked AND I had a new engine to put in so I just scrapped the cracked one. however, just helped a buddy with a tiny crack in his block on a 5.0L merc (1" long, barely leaking a drizzle of water).

We drilled the ends some - not through I don't think, then used a stepped bit (V-shaped drill bit") back and forth along the crack to clean it out. No idea how deep really, just sort of grinded until the rust was gone. Then wire brush, then acetone a few times to clean. Dried a while then jb weld. I used a small brush for one coat trying to really get it into the crack. We let that set a day then did a patch-type coat for 1" around the crack covering the crack. Maybe that would be a good one to include some glass strands in - we didn't.

It sure looks like a permanent fix - no idea how water could get out there, but it's only been a week or so running. No issues yet. I'd run it forever like that if it were mine. HOWEVER, in this case he'd be fine running it with the crack leaking as it was such a slow, minor leak it would not effect operation. If it was bigger and would ruin the engine and cause safety issues, i'm not so sure I'd fix it that way long-term.

 

[Wet dreamz]

Re: Mercrusier 3.0 litre block crack questions

Thanks for the info guys - you information is very helpful - I know it is external because I checked the oil after a quick run this earlier this year -then changed the oil to be sure it was clean - ran it a lot longer than I should have (didn't realize it was a crack before the first change but always check my oil for the milky colour). After running it I noticed no water at all in the oil.

I'll take all you advice and put it to good use - thanks so much in advance -
will let you know how it works out

 

[twostroke87]

Re: Mercrusier 3.0 litre block crack questions

i've done a many successful fixes with marine tex. great stuff, no drilling or anything. stuff it, dry, sand and paint never leaks again.

 

[Bondo]

Re: Mercrusier 3.0 litre block crack questions

OK...
assuming you have run it, or removed the pan plug to verify no water:

Ayuh,.... I've done Quite a few,... Suscessfully.... Only if cracked to the Outside of course,...

Whatever epoxy putty you use,.. Mash it in good 'n hard,...
Drill clean Though with a small drill at both ends, or any run-out crack's ends...
It ain't so much cleaning the actual Crack in preperation as the surrounding area,...
That's where the plastic will get it's Bite.... Shiney Metal gives the Best bond,...