Cracked Block! Options?

[Jstumbough]

I have a 1989 Mercruiser 3.0. It's been sitting for some time and I discovered a crack on the manifold side of the block, about one inch below the freeze plug. I had it running at 150? yesterday and the crack wasn't seeping at all. It just had minimal rust stains as the only indicator that it has ever leaked. The crack is horizontally about 4 inches long. The oil is also free of water. What are my options here?

 

[Alumarine]

If water isn't getting into the oil then you might get away with using JB weld.
I've heard drilling a small hole at each end of the crack might help stop it from spreading.
Depending on the location I would try it.
Maybe post a picture?

 

[Bondo]

The oil is also free of water. What are my options here?

Ayuh,..... If the oil is water free, run 'er til she dies,......

Put an epoxy patch on the outside,...

 

[NHGuy]

if you jb it first clean it with something effective like car painter's wax remover or acetone. Get it super dry. Warm the cracked part of the block with a heat gun, apply the JB and warm it to make it wick down into the crack. I've done this successfully myself.
The real reason it can succeed in boats more than in cars is that boats have very little pressure in their cooling systems. Whereas cars run hotter temps and 12 or 14 psi pressure. That pressure would be more likely to find a way past the epoxy.

 

[Jstumbough]

Thanks for the input. I purchased some JB Weld for the first time in my life.... I tried posting pics but am having trouble from my phone. I'll update when I make the "repair".

 

[H20Rat]

When doing that type of repair, I like to hit the surface with a flapper wheel on an angle grinder first. Helps clean it up, and the rough surface gives some grip to the jbweld. If you have ANY grease or contaminate left, the jbweld isn't going to stick very well.

 

[Boat Doctor1]

Been there done this= clean the affected crach- drill a small hole @ each end of crack- cut an alunimum plate to cover the cracked area- drill a few small holes in the plate- clean cracked area again & spray carb cleaner or brake clean on it - apply jb weld -lots! apply alu. plate- tape to hold plate if ness? go play when dry 1-2 days!!

 

[achris]

Can't stress enough, you MUST drill the relief holes at the ends of the crack. If you don't, the crack will continue to migrate. The purpose of the holes, and they only need to be 1/8", is to reduce the stress factor at the ends of the crack to 1. That stops the crack spreading.

 

[Jstumbough]

Do you drill the holes all the way through the block or just partially?

 

[ricohman]

through the end of the crack. Like right through.

 

[Jstumbough]

That makes me nervous considering it's not leaking water though the crack. But if that's what needs to be done....

 

[achris]

That makes me nervous considering it's not leaking water though the crack. But if that's what needs to be done....

Yes, it does need to be done, and all the way through, as already mentioned.