470 swap to 4.3L

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mrsemi05

Seaman Apprentice
Joined
May 26, 2009
Messages
31
hi im tryin to do a swap from a broken 470 to a good 4.3L and i got the motor for free its good running and its out of a blazer but i want to know what i will have to do to bolt it to my sterndrive and what i would have to do to the front mount??? any help much appreciated
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 470 swap to 4.3L

You will need the following, at least.
Marine carb, marine fuel pump, marine starter, marine alternator, marine ignition system to work with the shift interrupt system, exhaust Y pipe that mounts to the transom shield, marine exhaust manifolds, risers, elbows and hoses to hook to Y pipe, marine or truck cam, brass core plugs, thermsotat housing, side motor mounts, flywheel, coupler, and flywheel cover with rear mounts. stringers in the boat about 22 to 24" on center for the side motor mounts to mount on, along with all the brackets and hardware and linkages for all the items to mount on the engine.
 
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frank246

Petty Officer 1st Class
Joined
Jul 18, 2009
Messages
293
Re: 470 swap to 4.3L

From 470 L4 to 4.3 v6?
Not talking about the fact that the 4.3 engine is from a car and is not a marine engine!! Marine engines use different parts like gaskets, cam, spark protected starter, dyno, ignition, carb and so on. Unfortunately you can not use the marine certified bolt onns from the old 3.7.
You will need a rear engine mounting bellhousing that fits the 4.3, than you ll need the innertransom mounting plate that correspondent with the engine mounting bellhouse, watercooled exhaust manifolds for the 4.3 and the Y pipe and an engine coupler that fit the 4.3 flywheel. The side engine supports to the boat you ll have to fabricate yourselve and lots of other stuff. The gear from the outdrive would be ok for the 4.3.
Better look for a complete marine engine to do this swap or risk an explotion. good luck
just my 0.2 ct

(You type way faster than I do Don :))
 
Bondo

Bondo

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Apr 17, 2002
Messages
71,082
Re: 470 swap to 4.3L

Ayuh,... Your project is Doable,...
But,... As Noted,...
You're missing all the Important,,+ Expensive parts....
 
G

gettin'even

Petty Officer 3rd Class
Joined
Jul 28, 2009
Messages
93
Re: 470 swap to 4.3L

mrsemi05 said:
hi im tryin to do a swap from a broken 470 to a good 4.3L and i got the motor for free its good running and its out of a blazer but i want to know what i will have to do to bolt it to my sterndrive and what i would have to do to the front mount??? any help much appreciated
Click to expand...


In light of how many parts you're missing to do the conversion, I recommend selling the 4.3 for 100% profit and either.. 1) rebuild the 470 OR 2) get a reman 470.
 
M

mrsemi05

Seaman Apprentice
Joined
May 26, 2009
Messages
31
Re: 470 swap to 4.3L

okay i now know what i need to do this but i have a couple more ?? first is what do exhaust risers do??? and how hard is it to mod the stringers???

i have the hole truck that the motor came out of and the boat is a closed cooling system so im planning on keeping it closed thanks for all the help
 
4bait

4bait

Seaman
Joined
Dec 27, 2008
Messages
51
Re: 470 swap to 4.3L

You will still need Marine water cooled manifolds and exhaust risers.

The raw water pump in the leg pumps sea water through your heat exchanger to cool the engine coolant and then back out through the manifolds and risers to help cool the exhaust gases the exhaust and now warm sea water will then exit out through the prop.

as for the stringers I couldn't say what you would need to do without seeing them.

Cheers Andy
 
Don S

Don S

Honorary Moderator Emeritus
Joined
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Messages
62,321
Re: 470 swap to 4.3L

i have the hole truck that the motor came out of
Click to expand...
Doesn't matter, about the only thing you can use is the long block. You can not use the automotive electrical system or fuel system. It's an explosion hazard in a boat. The marine parts are sealed.

the boat is a closed cooling system so im planning on keeping it closed thanks for all the help
Click to expand...

You can't just take the closed cooling system off of a 470 and put it on a 4.3, the the heat exchanger may be too small if the 3" heat exchanger and doesn't have the outlets you need for the V engines, plus the expansion tank is part of the exhaust manifold on the 470 and can't be used on the V6.

Here is flow diagram of both a raw water cooled and a closed cooled system so you can see how they work. The risers are on top of the exhaust manifolds and is where the water from the cooling system mixes with the hot exhaust gasses.
 

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BRG25

Chief Petty Officer
Joined
Jul 13, 2001
Messages
528
Re: 470 swap to 4.3L

Wish the guy gave his location so I could read about this in the news following the explosion. I don't think he is listening to a word you guys are saying...
 
M

mrsemi05

Seaman Apprentice
Joined
May 26, 2009
Messages
31
Re: 470 swap to 4.3L

i am listening to what they are sayin so far i gots unable to use any auto stuff so meaning gotta get a new Dis, new coil, new alt, and new starter. not to metain all the other stuff like new coupler new flywheel new intake and carb witch i have found everything but the coupler for a good price (cheaper then fixin the 470) so now all im trying to find out is the mounting the engine in the engine bay
 
M

mrsemi05

Seaman Apprentice
Joined
May 26, 2009
Messages
31
Re: 470 swap to 4.3L

is there something i can do to help anyone in explainin an idea of how to mount this in there????
 
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mrsemi05

Seaman Apprentice
Joined
May 26, 2009
Messages
31
Re: 470 swap to 4.3L

thanks for the link and all the info!!!!!!! i will take a look at it now. i have been reading and searching this form for all the info i can get before i decide to dive into this thanks again for all the help
 
H

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: 470 swap to 4.3L

Howdy,


If you're going to use the engine in salt, it would be good to install closed cooling on the replacement engine. That will add around $700 (new) for a compatible closed cooling system.

You could find a used system for less probably.

You could look on ebay for the majority of parts you'll need to do the job. It's not going to be cheap.


The blazer engine should work ok. The camshaft might produce adequate torque at the wrong RPM though. Also, there could be a reversion problem with the automotive cam.


Your V-6 will need engine mounts on the side where the 3.7L engine has a front mount like other inline engines.


Most 18-20ft boats made in the last 20 years or so were offered with several different (inline/V-6/8) engines so you may already have the side mount blocks/stringer mounts . If you don't, you'll need to fiberglass in mounting points for the V-6 mounts. (you'll also need to buy mounts for the V-6 (like below from Ebasicpower)

http://www.ebasicpower.com/c/MER6G/Motor+Mounts+for+Mercruiser

You will also need the other stuff mentioned above. You can probably find it all on ebay. My guess is that if you buy it all one-by-one from ebay, used, you STILL may pay a lot more than you might pay by just buying a donor boat with a complete 4.3L package. (after parting out your 3.7L engine, drive, etc)


Your job is very "do-able" but you'll need a LOT of parts to make it work safe and reliably.


Cheers,

Rick
 
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frank246

Petty Officer 1st Class
Joined
Jul 18, 2009
Messages
293
Re: 470 swap to 4.3L

It is not that difficult to build the side engine supports if that is the only big issue, Just some rectangular tubing and bolting it to the floor and stringers. I also build my own engine support frame and bolted it to the (reNewed) floor and (new) stringers in mine. I went from a 140-L4 to a 225 V8. Build my own double wall ss exhaust.
The risers (as high as possible point above the waterline) are to prevent water entering the exhaust.
 

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mrsemi05

Seaman Apprentice
Joined
May 26, 2009
Messages
31
Re: 470 swap to 4.3L

frank246 thanks for the pics and how is that mount attached to the boat???? thats my biggest conncern at the moment and great job on that boat it looks great
 
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frank246

Petty Officer 1st Class
Joined
Jul 18, 2009
Messages
293
Re: 470 swap to 4.3L

Thanks,

If you save the photo an open it in Windows fiewer and zoom in you can see the holes in the frame bolted to the (3/4") floor with 1/4" ss Lag-screws. The 3 bigger 1/2" ss Lag-screwes bolted through the frame in the hull stringer.
The frame is powder-coated stainless 4"x2" tubing.
If you need some more info dont hesitate to ask.
Frank
 
M

mrsemi05

Seaman Apprentice
Joined
May 26, 2009
Messages
31
Re: 470 swap to 4.3L

okay this may be a dumb ??? but you bolted thu the hull??? im unable to check out the engine compartment since i am in Iraq. thanks for all the help
 
F

frank246

Petty Officer 1st Class
Joined
Jul 18, 2009
Messages
293
Re: 470 swap to 4.3L

No such thing as a dumb question, ah uhm, well in this case......:)
Not through the hull!!!
Bolted in to the stringers, the wood construction under the floor.
Good luck in Iraq
 

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