trying to fix cracked block

[rustybeater]

Hello, I have a 1993 johnson 90 hp cross flow motor. Long story short my motor chewed up a piston. I realized that all of the piston bores in the block were worn out of speck so, I sent it off to the machine shop and had all of the cylinders bored and ordered all new pistons. Once I got the block back from a machine shop I realized that the water jacket right below cylinder 4 had a crack in it. I know the right thing to do would be to get another block but I already had about $400 wrapped up in cost from the machine shop. (I wish he would have realized it while he had it). I decided I would try not to loose out on the money that I already spent and took the block to a welding shop where I had someone tig weld the block for me. I thought that would be the best fix. I went ahead and rebuilt the motor and she starts right up and sounds good. Then I realized that I am leaking water really bad from the area where the crack is. When I pulled the head off I realized that when they welded the crack they ground the metal down and it does not sit flush. I really dont know what to do. I am thinking about trying to put some RTV just on the water jacket to see if that can seal it. I really dont want to loose out on all of the money that I spent in this rebuild.

 

[F_R]

Marine Tex and file it down. Great stuff for patching.

 

[boobie]

As long as you're getting no water in the cylinders and it's an external leak use the Marine Tex as F_R says. Used it before myself and it's works good.

 

[emdsapmgr]

A few blocks will crack at the bottom of the cyls-due to residual water in the block during freezing temps. Since it's not a critical area, welding the crack should be fine. You've got another situation going on with the block not being parallel on all the cyl head face areas. Fortunately, it's the water jacket which is short, not the cylinder liner itself. FR has a great idea, build up the surface of the block with some MarineTex and sand it smooth-so that the head will sit parallel on the block. That stuff dries hard as nails and is impervious to water/oil, etc. A little extra gasket sealer in that area would not be a bad idea when you install the head gasket.

 

[rustybeater]

Ok, I will try to pick up some Marine Tex and see how it works. I am hoping that it works and that I can do it with the power head installed but I am not sure. The only thing that I am worried about is if I use gasket maker (RTV) is if it makes the head sit up higher and let water in the cylinders. I guess just do a compression check before I start it up?

 

[emdsapmgr]

Use that straight edge to be sure the block is as flat as the top of the cylinders. You should be able to work it with the power head installed. You should get good compression since the head gasket seal ring will seal the cyls. It's the rest of the gasket that seals the head to the cooling passages that you'll want to watch out for.