Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

[DeepBlue2010]

Hi,
I have access to an almost complete (no exhaust manifolds) 305 1994 2bbl carb non-vortec V8 mercruiser engine with only 350 hours on it. The block is cracked.
I am thinking of rebuilding it and replace 4.3LX 1996 Vortec 4bbl Carb V6. For the life of me, I can’t find any reliable info about the expected HP gain (if any) by doing that. Some sites rates my 4.3 at 175. Others at 195HP and some other sites rates it at 205. Same sites rates the 305 anywhere from 220 to 240. If my 4.3 is really 175 and I am moving to 220, it could be worth for me to do the “upgrade” but 195 to 220 is not worth I think. Any advice to help me make the decision will be much appreciated

 

[Tail_Gunner]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

No..i take it the 4.3 is tired or worn out?? 305 cracked with no exhaust is just burning money no matter how you look at it your going to rebuild that 305 and pay 400 just for a bad block...???? Just start planning your rebuild and look at the cost..

What type of budget are you looking at?

 

[DeepBlue2010]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

The 4.3 is not tired nore worn. It is working perfectly. Compression is steady around 140 PSI in all 6 cylinders. I am only suspecting that it might be an underpowered setup for the 2252. The only reason I bought the 305 is that the price was very low and all the Peripherals I needed (Alternator, Starter, etc)for my 4.3 was there there and looks much newer; mine are rusted. I know for sure I need an starter and alternator. The price I paid for the 305 is pretty much what I would have paid for these two alone. Then, I started thinking about the swap if I will get 40 or so HP in the process. I have no way to tell if my 4.3 is enough power for my 2252 cabin cruiser because I can’t put her in the water yet.

 

[Alwhite00]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

I would leave it alone, That cracked block is not re-buildable without tons of $$$ thrown at it.

LK

 

[Bondo]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

I would leave it alone, That cracked block is not re-buildable without tons of $$$ thrown at it.

LK

Ayuh,... 'ell,... it's an Anchor....

If ya long blocked to to a Vortec 350, you'd be pickin' up some serious horsepower....

A 4 bbl. fed 4.3l will out run a 305 2bbl. carbed motor, All day long....

No mention of any induction, so Hp numbers are kinda meaningless anyways...

 

[Utahboatnut]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

I agree with Bond-o 100% Stick with what you have, to me the 305 is a dog. Dont want to offend anyone but I just cant understand why they use a 305 when a 350 will fit in its place without hardly any additional weight, mounting considerations etc. I would say what you have right now would way outperform the 305 even if it were brand spankin new..

 

[bruceb58]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

Dont want to offend anyone but I just cant understand why they use a 305 when a 350 will fit in its place without hardly any additional weight, mounting considerations etc...

The two blocks are almost identical weight with the 350 maybe lighter because of the wider bore. The rotating weight is probably very close as well.

 

[DeepBlue2010]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

Guys,
I get that 4.3LX might outrun the 305 with its current configuration and based on this I might just use it as a donor and for some of the peripherals I need but here is a thought..

Why would it cost $$$$ to rebuild this engine. Assuming that the block is the only thing that needs replacement, we are looking at $250-$300 for a bored and honed block. Through another $200 for the unknown and some elbow grease and viola, you get a 5.0 up and running maybe not for my boat but someone else might have a use for it. Does this sound too good to be true? Am I missing something?

 

[matt167]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

Well, if you replace the block, you are effectively replacing the engine . don't expect to use more than the heads, crank and rods on the new 305, unless you can get a std bore engine, or whatever bore the current cracked block is, and then you can add rings to the old pistons, hone the bore to a nice crosshatch and stick it together/ hope for the best. by merely switching blocks and honing for a new crosshatch, you are not removing any wear, so you might as well buy another used engine.. Of course you can use the marine specifics on the new block, so you could go for any SBC
a 350 uses the same crankshaft ( balanced differently ), same basic engine except it has a 4" bore and not a 3.73 bore. You could get a good 350 for a few hundred from some GM vehicle because they are so common. add brass freeze/core plugs, marine profile cam and the marine externals you have. Much better.. If the 305 heads you have are a 416 ( HO ) casting, you could recover some money that way by selling them. In the automotive feild, you add them to a smogger 350 and it bumps the compression and makes a cheap tire burner

 

[TilliamWe]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

No.

 

[edsmax]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

The 305 with the 2bb non-vortec is junk. Like Bondo said, get a vortec 350 with a 4v and be prepared to be blown away.

 

[wca_tim]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

I'd rather have a vortec 4.3 than a 305. any day of the week. your 4.3 with 4 barrel will eat that 305 alive. a good running non-balance shaft 4.3 with vortec heads and an aftermarket manifold and carb will hit around 220 horsepower. either keep the 305 or spring for a 5.7 vortec... but that's not cheap, nor trivial once you buy a new exhaust, move engine mounts, etc... all the same things you'd have to do for the 305... if you're going to step up to a v8, get a real one. I see no use for a 305 when 350 cubic inches and more are available for equal or slightly more money. just sayin

 

[matt167]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

He's got V8 parts that will fit right on a 350 because the 350 and 305 are externally the same. So getting an engine, is really easy given all he would need is an automotive 350, brass core plugs and a marine cam. 350 would be cheap HP over a 4.3L. The 4.3 is a solid engine also, because it's 3/4 of a 350 but balanced to be even fire.

 

[markheck1]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

And it's not necessarily just the cost of rebuilding the engine, you still gotta buy new Exhaust manifolds, Not Cheap....

 

[smitty28]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

wouldnt he have to change outdrive gear ratio too? Goin from a v6 to a v8?

 

[Bondo]

Re: Upgrading Mercruiser 4.3LX V6 Vertec to a 305 1994 Non-Vortec, Is it worth it?

wouldnt he have to change outdrive gear ratio too? Goin from a v6 to a v8?

Ayuh,.... He sure will,.... The 4.3l comes with either the 1.84:1, or possibly the 1.65:1....

The later, might, possibly, be able to be Proped within reason....