Swap out Merc 470 for 4.3?

Steve Mahler

Petty Officer 1st Class
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Oct 10, 2006
Messages
361
I notice a lot of boats for sale with the dreaded (by me anyway) Merc 470 motor, really cheap - with motor issues. How hard would it be for a skilled marine mechanic to swap out the 470 for a 4.3 merc V6? Obviously the 4.3 would be shaped differently, but other than the doghouse; would the alpha outdrive mount be different? controls? wiring?

There is a very clean welcraft 19' in my town for sale with a blown 470 - it is very very cheap, and I am awful tempted to buy it and spend the winter looking for a 4.3 to swap; but not if it is a huge expensive swap.


Would a 3.0 be easier? I know power would be short.....
 

Bondo

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Apr 17, 2002
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70,464
Re: Swap out Merc 470 for 4.3?

Ayuh,...

The Motor,+ Transom assembley will have to be changed....

On the Bright side,... The existing Outdrive will work...
 

TilliamWe

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Dec 21, 2004
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Re: Swap out Merc 470 for 4.3?

And since everything inside the boat would have to be changed, you might as well go to a 5.7. But then you do run into front of engine accessory clearance issues. You also have to fabricate and install front motor mounts, as the 470 just has that one in the center.
It can be done, you just need a complete take out motor/transom/exhaust y-pipe donor.

The boat should be "free" to make it worthwhile.
 

chiefalen

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May 18, 2008
Messages
3,598
Re: Swap out Merc 470 for 4.3?

The 470 has side mounts, 3.0 has the front mount.
 

TilliamWe

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Dec 21, 2004
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Re: Swap out Merc 470 for 4.3?

The only 4 470s I have seen have all had front mounts.

And the one that my dad changed out for a guy had a front mount, because my father had to fabricate a whole front side mount system for the guy's boat. I didn't see it, but my father knows what a front mount is.
 

HT32BSX115

Supreme Mariner
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Dec 8, 2005
Messages
10,083
Re: Swap out Merc 470 for 4.3?

Most boats that size were actually available with several engine choices............so the side stringer mounting pads may be there anyway....

Problem is, if there's been any water intrusion into those stringers (or the transom for that matter....common on older boats),

The "really cheap" will end up not being so cheap after you replace the transom, floor, stringers, and the engine etc....
 

chiefalen

Captain
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May 18, 2008
Messages
3,598
Re: Swap out Merc 470 for 4.3?

Does have the front mount on the 470, different from the 3.0 front mount.

See younger guys have sharper minds.

And fresh new ideas.

Keep us old farts on our toes.

This is my point why go thru all this b.s, when in this economy you could get a little older boat with the package you want.

No changing out drives, motors, and such.

Unless this is a very special hull.

And it would be alot cheaper in the end.

Thanks Tilliamwe, keep me on my toes.
 

TilliamWe

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Dec 21, 2004
Messages
6,579
Re: Swap out Merc 470 for 4.3?

No problem Chief. And I totally agree with you, these kinds of swaps just usually aren't worth it. There should be a lot of "cheap" casted off boats available these days, that you should be able to find one that already has a 4.3 or a V8 in it.

Unless you just really love to work on boats, and not play in them!
 
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