Cracked Block

Post more information about where the crack is, how you think it happened, and what would you like as an outcome of this exercise, regarding performance, financial concerns, etc.

Welding is possible. It is not practical. Cast iron needs to be preheated for a good weld. The water jackets on marine engines are subject to rusting at an excessive rate. You could look for a used engine from an automotive application, and convert it for marine use. More specifics would help to guide you.

Get yourself a couple of tubes of JB Weld.

I agree with Vermin. I once had an engine with about $500 worth of porting work done in the cylinder head and after a couple years the water jacket pinholed into one of the intake ports. It became a hybrid before its time - gasoline/steam hybrid. I used JB Weld to patch the hole and had no problems for many years after. Sold it that way. My current hot rod has a boss made of JB to extend the block so I could change the starter motor mount. Good stuff.

jhammond

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www.patent-innovations.com

Somtimes it works sometimes not. Son had an old chevy that He repaired with jb weld and it worked fine. However I had a lawn tractor with a crack in the crank case. tried repairing twice did not work. But I agree its worth a shot, if it doesn't work your only out a couple bucks.

oilcan13

Hello oilcan,
Hope you are fine.

I could have written this on most or all the 'quick-fix' answers here:
In this case, no one here has enough info' to give advice. It may be the block is completely split in half or, it may be a small corner of say 5 mm has chipped off.
And............It will not be "just a couple of bucks"
It would if it was a car. But you cannot take that reasoning and apply it to a boat. A 'quick-fix' may well appear to work just fine. Until the boat is five miles (8 Km) away from help if it breaks down!
If the boat is used exclusively on lakes where the land can be 'rowed to' fine. But even some lakes are like inland seas!................ When discussing anything about a boat there is no 'half measures'. Get it right first time even if it does mean quite a bit extra work, or................. do not bother with it at all, which is the same as a quick fix.

I am really surprised you and others, not only you, can give such a negative reply.

This is an engineering site remember? And I know that may sound pompous, and I apologise for that. I do apologise for trying to give proper advice and waiting for the OP to reply. We do not even know if the block is steel or aluminum yet so how can we give sensible advice?

Do not forget, if it is a boat with a substantial inboard Engine, it will not be easy to get back to land, unless there is a spare outboard and a place to hang it?

Absolutely no insult intended to anyone here, OK?
Take care.

What you may have forgotten is cleanliness. You need to clean the crack with something that gets rid of all greases/oils etc and to NOT touch the area with your fingers before sealing with JBWeld.

To make the repair even stronger, I do believe there is a "primer" to use before using the JBWeld.....

Belzona is the best. I have saves $$$$ using it. Of course JB weld works too. In my experinace Belzona performed much better and it is chaeper too.

Well, fine! I get a bunch of guys agreeing with me, and I don't even get a good answer!!!

Hello Guest,[p]A Marine Engine probably goes through a lot more stress than an ordinary vehicle engine.[p]

You say it is a 5.5 L Mercury Engine.

I do not think is enough info' to be able to search details for this thread.

Can you tell me/us what year it was built,

If it is a dedicated Marine or freshwater Engine please?

And what the block is? Steel, aluminum?

listen to vermin GET SOME JB WELD

Once again you guys need engine help but offer next to no information for us to go on ?! If you are not capable of providing the info. required for us to at least have a clue , then you should probably see your nearest dealer for help.

If you are mechanically inclined , there is technical help available here. If you are not mechanically inclined , a repair facility is your best bet.

Hello machine haed,

Well put.

I see there is no reply from the OP? Unless they have replied in there user name, but I can't see them.

I would have thought if the block is cracked, and we do not know if it is 'critical' yet, but the very least that needs to be done is the head removed.

I have been trying to think how the block got cracked in the first place. The only way I could imagine it happening was if the boat hit something hard at speed. That is the advantage of a 'jet' drive. There is no metal to hit any rocks? But we do not know what kind of drive it is............. in-board, in-board/outboard, jet, outboard????????

Frustrating when no help is given in reply by the OP?

Take care.

may be OP meant to say " head cracked bloke" in his boat!

just joking...thought of adding some fun.

Hello Sisira,

How are you?

Yes maybe the OP did mean to say that! ;=)

Take care.

hey check out this stuff ... www.locknstich.com

Your block cracked for a reason this is not an insignificant event. In the world of what is possible and what should be done it is simple. ID and repair the over heating problem and replace your block/engine. It's so easy to spend your money but you have some serious considerations that don't apply to many recreational activities. The result of going dead in the water can range from embarrassment to a life threatening catastrophe. Ship/boat repairs demand a higher level of reliability and quality than many other recreational applications. There are no tow trucks, no AAA and no road maps with clear and easy instructions for help to follow. Throw in some bad weather, two screaming kids and a wife that never forgets makes maximum reliability absolutely essential.

There are old boatmen and there are bold boatmen but there are no old bold boatmen. Fix it right.

Years ago, before JBWeld, we would drill and tap and plug with a screw, then drill again, slightly overlapping the previous one, so that they are were locked into each other.....each screw would be "glued in" using gasket sealant!!!

If JBWeld was used instead, it would give a reasonable fix I feel......even for a boat.

Also, anyone going "Offshore" without a secondary propulsion system is living dangerously.....but of course many do.....

Hello Andy,

Also, anyone going "Offshore" without a secondary propulsion system is living dangerously..... but of course many do.....

This was the point I was trying to make in a previous post. It is hard or impossible to use oars, so a small 'electric' auxiliary' is sometimes the answer, especially if the weather is unpredictable and or you are out in tidal waters? Or go out with a friend in another boat perhaps?

Take care.

Where is it cracked?.Is it accessable for drilling? If so, research

"steel stitch weld"repair.

Works great, lasts a long time.

I have had some success welding blocks, by preheating the area, grinding a v groove along the crack, and drilling a hole at each end of the crack to prevent spreading.I then braze the crack a little at the time, and peen the bead with a ballpeen hammer to relieve stress, then braze a little more, etc.Wrap the work piece in fiberglass insulation and allow it to cool slowly.

By the way, some Mercury engines rotate opposite from a car engine,so an easy swap is not possible.They added one extra gear in the newer out drives which causes this.

Good luck

EZStreet

Hello Guest,

I have been thinking about your broken block a lot, which is not like me! ;=)

Just a thought here .................. If the block cracked, does it mean there was uneven stain on it from differential torque settings, ............. which should be the same?

Take care.

Not nescessarily. Could have been frozen because of not winterizing the block, which is a more common reason.Other reasons are extreme corrosion from salt water, not being properly purged with fresh water after use in brackish water or ocean.

I have seen bolts broken for over torque, but never seen a block cracked from excessive or uneven torque.

Hello Guest,

I thank you for your reply post, and agree with your reasoning. Odd though why it should have broken.

Take care.

All that and cracks because of over heating, and just a bad casting at the plant.