Cracked block repair advice

[Anyox]

Last night I discovered my very first cracked block. I have a 1982 Johnson V4 90hp. The crack is on the lower right cylinder through the water jacket to the bottom exterior of the block at about 5 o'clock relative to the center of the piston. This means that the crack is in a hard to access location for anything linear (drill, etc). The crack extends from the gasket surface back into the block about 7/8-1 inch and is 1-1.5 mm across at the face. The cylinder itself is in fine condition without loss of compression.

I've been reading around on the forums that people use a variety of products to fix cracks from Marine-Tex, JB Weld, primer and hardener recently, all the way to taking the block to a welder.

My question is, what would you recommend I do to fix this crack that would be long lasting, not make the situation worse and cost effective (I'm a graduate student on a budget).

I've used Marine-Tex before to repair screw holes in the fiberglass...that required me drilling a larger hole to prepare the surface. Am I going to need to drill the block to make the crack larger before I make the repair? Do you think I will be removing the block from the engine to make this repair?

Thanks for any advice!

 

[iwombat]

Re: Cracked block repair advice

Unless I had a rare block, I'd be looking for another one in decent condition. Look on CL in your area for parts motors. They're pretty easy to find here. If your close, I can even offer you one of mine. If you're set on fixing it, welding is the only reliable way to go. Whatever you choose, you'll be removing the powerhead and stripping the block down anyway. There's no shortcuts on this one.

 

[Anyox]

Re: Cracked block repair advice

So I've been reading other threads today and still haven't determined whether I should use MarineTex or JB Weld. Also does anyone have an opinion if this should be a setting for original JB Weld or MarineWeld? The boat is regularly used in both fresh and salt water.

It seems that people are recommending a bunch of time be spent on site prep no matter what I do. Does that entail drilling the crack all the way to the end or just drilling out the end of the crack...I was a little confused.

Last, one thread suggested that using a heat gun with JB Weld would make it more fluid and run into small crevices. Anyone else done this?

 

[wilde1j]

Re: Cracked block repair advice

Depending on exactly where, I would consider welding in place, but only if you have an excellent TIG welder with a light touch. The crack will likely grow unless welded. What's often the challenge is machining the weld if it's part of the gasket seating area. The good news is the sleeve is apparently OK.

 

[jonesg]

Re: Cracked block repair advice

see this.
http://www.aluminumrepair.com/video_new.asp

 

[14ftgrumman]

Re: Cracked block repair advice

The alumalloy works, but on a block you need more heat and concentrated heat than a propane torch (plumber's torch) can give. This is where you need an oxy-aceletene torch, but be careful about how much heat you use. The alumalloy needs 600 deg F. to flow. You could always make your block into a puddle if too much heat is used.

 

[Anyox]

Re: Cracked block repair advice

That alumalloy looks like it would work great, but does anyone have experience with it? Would it be possible to get a hot enough torch if I just used a slightly different gas blend that was still available in a handheld bottle? Is this a significantly better option than JB Weld for a longer term fix? I don't want to be a cheapskate and all of these options sound better than a new block, but is $65+tax going to do the job a lot better/longer than $7? Thanks for the thoughts!

 

[wilde1j]

Re: Cracked block repair advice

Wow, you're considering learning to weld on a very challenging weld. More guts than I have. I'd find a good TIG welder, who could do it right in less than an hour.

 

[rolmops]

Re: Cracked block repair advice

Unless I had a rare block, I'd be looking for another one in decent condition. Look on CL in your area for parts motors. They're pretty easy to find here. If your close, I can even offer you one of mine. If you're set on fixing it, welding is the only reliable way to go. Whatever you choose, you'll be removing the powerhead and stripping the block down anyway. There's no shortcuts on this one.

This is the only safe and reliable way to go.
You do not want to be out on the water toward evening and near a storm with a broken engine because of a sloppy repair

 

[Anyox]

Re: Cracked block repair advice

In its current condition I have gone on a number of trips with it (about 15-20 total) that have lasted about an hour, many at high RPM. Is there threat that mainly this would fail in an overheating way or is there potential for true catastrophic failure?

From a bunch of other threads people have had JB Weld repairs in place for up to a decade or more. Are there people not reporting failures, personal experiences with these repairs failing, or why am I being so strongly steared towards TIG welding? I'm not questioning anyone's credentials, just trying to understand the background of experience that I am currently being guided by.

 

[wilde1j]

Re: Cracked block repair advice

My dad had a boat shop for many years and had a really good TIG welder buddy from Los Alamos, NM who did a few cracked blocks. All were done with no guarantees, but none ever came back failed either. The guy was a very talented welder.

 

[kenmyfam]

Re: Cracked block repair advice

First choice would be replace the block
Second choice would be tig weld by a known good welder.
Having said that depending on the quality of the original casting you can end up "chasing" the crack no matter how good a welder you are.
Not the welders fault but the nature of the casting.

 

[rolmops]

Re: Cracked block repair advice

In its current condition I have gone on a number of trips with it (about 15-20 total) that have lasted about an hour, many at high RPM. Is there threat that mainly this would fail in an overheating way or is there potential for true catastrophic failure?

From a bunch of other threads people have had JB Weld repairs in place for up to a decade or more. Are there people not reporting failures, personal experiences with these repairs failing, or why am I being so strongly steared towards TIG welding? I'm not questioning anyone's credentials, just trying to understand the background of experience that I am currently being guided by.

My reason for TIG welding is based on boating safety rule #1. Do not take any chances.The water is unforgiving.
If however you only plan to go to a local lake with plenty of other boaters around you,you can take a bit more of a chance