Engine Swap

fireguync

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I just bought a 1994 Chaparral 1930 SST with a Mercruiser/GM 305. When I bought the boat the current owner explained that the boat was winterized and the engine block still cracked. Upon looking at it it is more than a "crack" I have since purchased a long block to replace it. The company I purchased the long block through sold me on upgrading to a 5.7 from the 5.0. I upgraded some of the internals to give me a little more HP. What do I need to do for the fuel system in this case? It is the mechanical fuel pump with I believe to be a 2 barrel carb. If I upgrade to a 4bbl carb where do you recommend me getting the intake and carb? Also will the stop mechanical fuel pump still work or do I need to find a high volume one? Thank you and stay safe.
 

Scott Danforth

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Which heads are on the motor?

If you upgraded to vortec heads you will need a new manifold

If you didn't, you can keep your existing manifold and carb. Just need to rejet
 

jimmbo

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The OEM carb will likely be too small for the larger engine. Rejetting wouldn't solve anything. Add to the fact that larger engine will require more air at Idle which will mess up the Relationship between the Throttle Plates and the Idle Transfer Slots, on a carb sized for a smaller engine

If you want to go to a 4bbl, a Holley 4175 650 Spreadbore would be a good choice
Intake: Edelbrock makes several Marine Intakes. But I can't get the Links to work
 
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fireguync

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I stayed with the standard 5.7 non vortec heads. The gentlemen from the engine place said I would be around 300HP. So the current fuel delivery should work?
 

fireguync

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The OEM carb will likely be too small for the larger engine. Rejetting wouldn't solve anything. Add to the fact that larger engine will require more air at Idle which will mess up the Relationship between the Throttle Plates and the Idle Transfer Slots, on a carb sized for a smaller engine
So what do you recommend?
 

fireguync

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Which heads are on the motor?

If you upgraded to vortec heads you will need a new manifold

If you didn't, you can keep your existing manifold and carb. Just need to rejet
I stayed with the standard 5.7 non vortec heads. The gentlemen from the engine place said I would be around 300HP. So the current fuel delivery should work?
 

jimmbo

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I stayed with the standard 5.7 non vortec heads. The gentlemen from the engine place said I would be around 300HP. So the current fuel delivery should work?
With the carb I suggest, and the Vortec Heads you will get close to 300hp, that is with the stock Mercruiser Cam Grind
Beware that Cams that are great for cars/trucks are 99% of the time not very good for boats, so pick your Cam carefully
 

Bondo

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I upgraded some of the internals to give me a little more HP. What do I need to do for the fuel system in this case?
Ayuh,..... Welcome Aboard,...... What did you do internally,..??

The Oem fuel pump will be just fine,.....
For induction, I suggest a cast iron intake from michigan motors, 'n the an edlebrock 1409 4bbl. carb,.....
The 1409 is exactly the same carb Merc has used for many years now, so throttle brackets, fuel lines, 'n such can be bought off the shelf,.....
It's a small bolt pattern semi-spread bore, so the smaller primaries work well, 'n when ya drop the throttle, it'll really come to life,.....

I agree with the others, I donno what you did for up-grades, but the Vortec heads are way better, 'n make more usable power in a boat motor,....
 

fireguync

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Ayuh,..... Welcome Aboard,...... What did you do internally,..??

The Oem fuel pump will be just fine,.....
For induction, I suggest a cast iron intake from michigan motors, 'n the an edlebrock 1409 4bbl. carb,.....
The 1409 is exactly the same carb Merc has used for many years now, so throttle brackets, fuel lines, 'n such can be bought off the shelf,.....
It's a small bolt pattern semi-spread bore, so the smaller primaries work well, 'n when ya drop the throttle, it'll really come to life,.....

I agree with the others, I donno what you did for up-grades, but the Vortec heads are way better, 'n make more usable power in a boat motor,....
So I went through MABBCO for the long block. I did a HP marine camshaft, Double row timing set, high volume oil pump, new valve springs for the camshaft, roller lifters, and flat top pistons.
 

flashback

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I might have missed it but you said you just bought the boat and your in the process of swapping. Don't use any of the old 94 engine parts on the new motor . They bite back!
 

flashback

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Well anything bolted to the motor that's 30 years old and fails is a bi+#$ to replace when the engine is in the boat.. guess what I'm saying is start off with new stuff...
 

flashback

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I'm thinking you don't really know what the condition of the outdrive or hull structure is since you bought it knowing the engine is trash you couldn't take a ride.. just saying that there may be more than motor needed..
 

jimmbo

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I will assume you are referring to things like Exhaust Manifolds/Risers, Water Pump, the miles of Hose Mercruiser uses on their Engines.
 

fireguync

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I will assume you are referring to things like Exhaust Manifolds/Risers, Water Pump, the miles of Hose Mercruiser uses on their Engines.
I did put it in the lake and take it for a ride. The crack produced a lot of water so not much riding. It stayed a-float and the outdrive appeared to operate well. Since I pull the outdrive to change the motor I am replacing the water pump, gimble, bellows, and u-joint while in there. Trying to find a kit that is available is the hard part.
 

flashback

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The shift mechanism and lower cable is probably shot as well.. you have a boat that likely wasn't cared for.. cracked engine block etc..
 

Scott Danforth

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I stayed with the standard 5.7 non vortec heads. The gentlemen from the engine place said I would be around 300HP. So the current fuel delivery should work?

So I went through MABBCO for the long block. I did a HP marine camshaft, Double row timing set, high volume oil pump, new valve springs for the camshaft, roller lifters, and flat top pistons.

You built a 330+ hp capable bottom end with 260-270hp capable heads

The motor came with flat tops from the factory. So the only thing you added was timing chain

If you want 300hp, you need vortec heads or you need to spin the motor faster than the drive wants to spin
 

flashback

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The boat b

The boat by the looks of it has been very well maintained. I will check them
And there lies the gremlins, a boat that old.(I have one) can look like new cosmetically but unfortunately it seems no one maintains the vitals.. I hope you have a positive outcome just understand that the chances of more chores are a possibility..
 
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