Cracked Block Replace 5.0 Or 5.7

SPIDERSS · Jun 1, 2009

Ok pull the classic da move. Missed plug when I drained boat last winter now have a 5" crack in block. My boat is a 2002 tahoe with a 5.0 motor carb.
Not sure which way to go. I am going to have to replace unless someone knows magic. So was looking at long blocks and seeing very little difference in price between 305 and 350 motors however not sure what will and will not fit from one to the other and what parts I may need that will not fit. Not sure my marriage can afford another mistake on this boat at this point looks to be a good upgrade. Also does anyone know what I should and should not look for in a new motor. Thanks

Gary H NC · Jun 1, 2009

Re: Cracked Block Replace 5.0 Or 5.7

Go with the 350.....all the external parts will bolt right up.

IVAZ · Jun 1, 2009

Re: Cracked Block Replace 5.0 Or 5.7

Definitely go to a 350. The only difference between the 305 and 350 is a bigger bore on the 350. Everything else is the same. The 350 might like bigger jets in the current carb you have.
Best engine is going to be one already designated for marine use. A truck engine can be converted to marine use easy if that?s the route you go.

180shabah · Jun 1, 2009

Re: Cracked Block Replace 5.0 Or 5.7

Carbed 305 probably has a 1.65:1 ratio in the drive(same as the MPI 4.3's).

Depending on what you are currently running for a prop you may need to re-gear/replace the upper unit in the drive. If you have a fairly low pitch prop, you might get away with just a prop change.

SPIDERSS · Jun 2, 2009

Re: Cracked Block Replace 5.0 Or 5.7

Ok I am going with the 350 anyone have anything I should look out for when buying a longblock? Have seen some on ebay for 1800-2600 sound right? Or any other company's anyone has got one from good or bad? Sorry asking alot of questions but don't want to make another mistake.

rbh · Jun 2, 2009

Re: Cracked Block Replace 5.0 Or 5.7

A crack is never a good thing but spending lots of money to correct a mistake is not good either. Have you seen water in the oil (is the crack on the oil side or just the outer wall). Three things you could try if it is just on the outer wall. first run it and see if it will seal its self (rust up), second clean and apply a JB weld style appoxy sealer, third drill out the ends of the crack, tap in small plugs to stop the crack from running and find a good welder that can do cast steel.
just a thought
rob

danond · Jun 2, 2009

Re: Cracked Block Replace 5.0 Or 5.7

So many "I missed one plug" stories. I think the actual situation is "I didn't winterize at all, but missing one drain plug sounds less embarrassing."

A cracked block in a boat is no better than an anchor. Don't fix it with JB weld, it isn't worth sinking the boat. Get a new block, and good winterization prevents the issue in the future.

ringmaster72 · Jun 2, 2009

Re: Cracked Block Replace 5.0 Or 5.7

danond said:
So many "I missed one plug" stories. I think the actual situation is "I didn't winterize at all, but missing one drain plug sounds less embarrassing."

A cracked block in a boat is no better than an anchor. Don't fix it with JB weld, it isn't worth sinking the boat. Get a new block, and good winterization prevents the issue in the future.

WTF? What does a cracked block have to do with sinking the boat? And if the crack is only on the outside and not inside where the water can get to the oil what will it hurt?

Bottom line is if the oil is not milky after running the boat, then just JB Weld the crack and you are fine.

180shabah · Jun 2, 2009

Re: Cracked Block Replace 5.0 Or 5.7

External crack will dump cooling water into the bilge anytime the engine is running.

I agree that if there are no internal cracks, JB (or other epoxy) is an acceptable solution.

No internal cracks would not be common, but it is possible. Pressure test the block and proceed from there.

SPIDERSS · Jun 2, 2009

Re: Cracked Block Replace 5.0 Or 5.7

I did just miss one plug not sure that is any less embarrassing. I know there are alot of those stories. It was a dumb mistake just looking for some advice. Anyone know who sells a good long block? Thanks John

180shabah · Jun 2, 2009

Re: Cracked Block Replace 5.0 Or 5.7

Michiganmotorz (also sells on ebay) seems to have a good reputation, also several members on here have had good experiences with Rapido marine in FL.

IVAZ · Jun 2, 2009

Re: Cracked Block Replace 5.0 Or 5.7

ringmaster72 said:
WTF? What does a cracked block have to do with sinking the boat? And if the crack is only on the outside and not inside where the water can get to the oil what will it hurt?

Bottom line is if the oil is not milky after running the boat, then just JB Weld the crack and you are fine.

JB weld to fix a block is a total half a** job. Although it can work temporarly, you never know when the jimmy riggin is going to come back and bite you in the rear.
If the op has the coin to do it the correct way, why steer him to a half a** way of fixing it?

sarantis · Jun 2, 2009

Re: Cracked Block Replace 5.0 Or 5.7

I want to help you with your marriage.I understand you.So be carefull.You said your boat was 2002.So evidently the engine is 1piece rear seal.Don't buy a rebuilt engine of older vintage that may be a 2piece rear seal.Some expensive things don't fit.

ringmaster72 · Jun 3, 2009

Re: Cracked Block Replace 5.0 Or 5.7

IVAZ said:
JB weld to fix a block is a total half a** job. Although it can work temporarly, you never know when the jimmy riggin is going to come back and bite you in the rear.
If the op has the coin to do it the correct way, why steer him to a half a** way of fixing it?

It may not be the best way, but give me a break. It could last for years with zero trouble. It hurts nothing to try it, if it lasts a season and then lets go who cares. he can either jb weld it again or go another route. I would not use the jb weld method, but there is nothing wrong with doing it that way to get you by.

IVAZ · Jun 3, 2009

Re: Cracked Block Replace 5.0 Or 5.7

ringmaster72 said:
It may not be the best way, but give me a break. It could last for years with zero trouble. It hurts nothing to try it, if it lasts a season and then lets go who cares. he can either jb weld it again or go another route. I would not use the jb weld method, but there is nothing wrong with doing it that way to get you by.

If you have to do it because you simply can?t afford the new block is one thing. To have the money and half a** it anyway just does not make sense. With the JB weld there is also no guaranty it will last a season either. It might be years or hours. I could never fully enjoy the lake wondering when the JB might let go.

180shabah · Jun 3, 2009

Re: Cracked Block Replace 5.0 Or 5.7

JB weld to fix a block is a total half a** job. Although it can work temporarly, you never know when the jimmy riggin is going to come back and bite you in the rear.

IF the epoxy lets go(not likely if done right, some of them are stronger than the iron we're repairing), it'll leak - not exactly the end of the world.

Of course this is all acedemic at this point, we still don't know the extent of the damage to the block.

If the op has the coin to do it the correct way, why steer him to a half a** way of fixing it?

Jealous? Or just enjoy spending money when you don't need to?

cooter2506 · Jun 3, 2009

Re: Cracked Block Replace 5.0 Or 5.7

We JB welded my father in laws 1988 OMC 4.3, 12 years ago and never looked back. If it is done right then it will last forever. If he has the money and wants to repower then go for it. If he has the money and just wants to repair it with JB then go for it. That will only work if the crack is external if it is interna too he has no choice. BUt repowering to a 350 you will see a difference in performance.

IVAZ · Jun 3, 2009

Re: Cracked Block Replace 5.0 Or 5.7

Shabba,
I cant see how JB would be stronger than iron.
Replacing a cracked block hardly sounds like "spending money when you dont need to".

IVAZ · Jun 3, 2009

Re: Cracked Block Replace 5.0 Or 5.7

Regardless of the JB working or not, it?s still a half a** job.
I work for an industrial construction company, I can assure you if we tried to repair any pipe or vessel with JB we would be laughed at. Some of the stuff we repair is considerably under less stress than an engine also.
If the op does not mind half a**ing and chooses the JB, I wish him the best of luck and hope it last a long time.

Gary H NC · Jun 3, 2009

Re: Cracked Block Replace 5.0 Or 5.7

If the crack is ground out and drilled at each end the JB may hold.
I have seen many that JB was used on and was just gobbed over the crack...
It may last a day or a year or so...It will fail at some point no matter how it was used.
The crack continues to rust under the JB weld and eventually will leak..
Half A**ed in my opinion.

Cracked Block Replace 5.0 Or 5.7

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