Boat Stern Drive Repair

[nocheepgas]

A buddy had a problem with his boat, the coupler between the engine and the out drive blew and took part of the stern drive bellhousing with it.



It had some pretty good cracks, but where they occured the part was more of a scattershield than structural, which is why it received the impact.



Had a difficult time getting to some areas to clean adequately, especially in the corner but had access to both sides to make the repair go pretty easily. A replacement part from Penta/Volvo which purchased OMC (?) was going to run $1,100.00. So I told my buddy I could fix it for $500.00 LOL I think I'll get lunch out of him???





3/32" Pure Tungsten
200 Amps-throttled back some
20 CFH Argon
1.8 PPS

[SundownIII]

You may find that you have to build those cracks up and grind them out several times (buttering) to get the junk out of that casting. You may also try a little preheat. Repairs look mighty cold to me. Based on the mass involved, the Sync 200 may be a little underpowered for the task at hand. 25% Helium in your argon would help increase the arc temp also.

I wouldn't want that part leaving my shop looking like that. Just saying, that if you're going to do a job, do it right. What I'm seeing is A LOT of porosity which translates to a weak spot.

Oh, and it looks like you just need a few more tools on your welding table.

[nocheepgas]

You may find that you have to build those cracks up and grind them out several times (buttering) to get the junk out of that casting. You may also try a little preheat. Repairs look mighty cold to me. Based on the mass involved, the Sync 200 may be a little underpowered for the task at hand. 25% Helium in your argon would help increase the arc temp also.

I wouldn't want that part leaving my shop looking like that. Just saying, that if you're going to do a job, do it right. What I'm seeing is A LOT (
Really? I can see it better here than you can in the pics, except for pic #4 at the top and bottom the rest looks pretty solid)of porosity which translates to a weak spot.

Oh, and it looks like you just need a few more tools on your welding table.

Thanks Sundown,
If I had a shop I probably would do a better job on it
I did preheated it with a rosebud, and also used the heat to massage the parts back closer to their original orientation. Yes there is some slight porosity at the start/stop but overall I believe it has good structural integrity.

[SundownIII]

nocheapgas,

If you don't want honest opinions then you shouldn't post photos.

You say the part is more a scattershield and not structural. That's not exactly correct. That part serves as the rear motor mount for the engine. On a casting such as that, it's almost impossible to look at it and say it doesn't need to be structural.

What you showed in your photos was the "easy fix". What I saw attempted there was poor preparation of the crack (you just ground the surface rather than grinding down into the crack), not enough heat, and a major crater in your bead. I already mentioned the porosity from not building the base metal up before trying to do the final bead. What was done there could have been done with marine tex and would have been as strong and better looking.

Hard to tell from the photos but there appears to be major deformation (from impact) to the side of the housing in the area of the second (major) crack. I'm not sure what the tolerances are for the Volvo unit, but that in itself would cause major problems with the Mercruiser.

I don't see any attempt to repair the second, more drastic crack, or the crack that goes around the side of the housing. I would hope that you plan to grind the crack almost totally out rather than just grinding the surface.

That housing may well exceed the capabilities of the Sync 200, not necessarily because of the thickness but because of the overall mass.

I'm not trying to "pick on you" but I have been doing marine aluminum repairs for a considerable time. What I see done there is not done right.

With that said I'll take my keyboard and leave.

[Desertrider33]

I agree about the need to grind the cracks into a Vee.

I do aluminum wheel repairs on occasion and the first thing I do is drill a hole all the way through at each end of the crack to keep it from running. Then I grind out the crack into a deep, wide V with about a 3/32 to 1/8" gap at the bottom (I use the filler rod as a guide to gap width). I put in the root, which I make sure penetrates fully through the other side. After that, I fill up the V with however many passes it takes to fill it, making sure the cap pass fully fills at the toes and all across the middle, so I have enough meat to grind down and not have any low spots after the grinding is done, on both sides. The multiple passes also help to burn out impurities in the metal.

The problem with just grinding the surface and not grinding out the crack into a V, then welding from both sides, is that you've still got a crack inside there. Doing the repair that way, you've covered up the crack on both sides, but the crack still exists in the middle of the wall and will come back to the surface later, eventually.

The other problem with not grinding out the crack into a V, is that you have no way to clean the metal inside the crack. You have all that impurity, oxidation, oil, etc that has found it's way into the crack and cannot be cleaned out without grinding out the crack all the way through it's depth.

That impurity haunts you when you try to weld up the crack. No matter how well you clean the surface and how hot you get it with the torch or pre-heat, or how many times you go back over it in the hopes of heating out the impurities, those impurities are still in there cause you can't clean them out without grinding out the crack fully.

[Tryagn5]

Sync 200 is to small for that, I have owned a sync 200 and on aluminum the real capacity is about 3/16. If I were to off repaired that I would have used my spoolgun if it would have fit in there. With that said if the parts failed thoose parts are easy found used for the 200-300 range, at most!
Kevin

[nocheepgas]

No, I appreciate the feedback. The repair area was ground out, I did not show a photo of that, only one that showed the initial cleaning with a 3M rolloc surface conditioning disc. I helped disassemble the boat, and I know for a fact it is not a structural part. Yes there was some remaining deformation. A casting such as this that was subjected to the impact of the engine/outdrive coupling experiencing a rapid disassembly cannot easily be brought back into the original factory specs as far as the shape. The mounting surface was unaffected, and my friend was happy to not have t ospend $1,100 to replace the part. He was unable to find a used part.

[jrscgsr]

hey nocheepgas. I have the same feelings as the other guys looks cold and dirty. Also you shoudn't be using pure tungsten on an ac squarewave machine, use Ceriated tungsten. Its in the owners manual.

[Frank865]

hey nocheepgas. I have the same feelings as the other guys looks cold and dirty. Also you shoudn't be using pure tungsten on an ac squarewave machine, use Ceriated tungsten. Its in the owners manual.

WTF are you talking about????
The owners manual says pure tungsten isn't recommended for steel! He's doing aluminum.
Green tungsten is fine.

[jrscgsr]

WTF are you talking about????
The owners manual says pure tungsten isn't recommended for steel! He's doing aluminum.
Green tungsten is fine.

WTF am I talking about? WTF are you talking about? I never even mentioned steel. Read it again before trying to jump on someone for what they wrote without even knowing the facts. The pure tung is not ideal for aluminum on an advanced square wave machine, ceriated or lanthiated is a much better choice of tungsten if you have an advanced square wave machine welding aluminum because they carry more heat without balling on the end, and it's recommended to grind it to a modified point because it will provide better arc stability and arc starting. It is written in the "Tig Handbook" downloadable on this site under the tungstens section.