305 Mercruiser Vortec Heads ?

[Davidsgara]

I have just come across an EFI kit for sale on eBay that supposedly came off a 2004 5.0 (same year as mine) any thoughts if this would be a better option than going to the Edelbrock 4 bbl ? Also would it be a fairly straight forward install? I still believe that the 4bbl carburetor will give me a better horse power increase than the TBI kit?

 

[scoflaw]

What setup did you have originally. What was wrong with it ? EFI kit would work if you had ALL the parts. No horsepower gain or loss either way.

 

[Davidsgara]

Its currently a 2 barrel Mercarb and hasen't been giving me any problems it starts and runs fine.
I was looking at going to an Edelbrock 2516 marine intake manifold and 4 Barrel 600 cfm Eldelbrock carburator which should get me a 30 HP increase and better tourque right across the rev range.
Its currently a 220HP set up and was hoping to get some more low end torque as its a fairly heavy 21ft Searay Sport 200 boat.
Wouldn't the EFI get me up to 260HP ? I thought the EFI version was around 260hp?

 

[scoflaw]

Might want to look at what cams were used in those diff. applications.

 

[Davidsgara]

I have been reading and seem to think that both engines (2004 5.0L) have the same internals just different fuel systems.
The version for sale on ebay (EFI) has two fuel injectors where the carburetor would normally sit.
Its not the MPI version that has an injector for each cylinder mounted closer to the intake valve.
The the MPI version will deliver a more precise fuel delivery to each cylinder.
The 5.0 EFI was rated at 240 HP (4,400-4,800 RPM) and the 5.0 MPI is rated at 260 HP (4,600 - 5,000 RPM).
My existing carburated version is 220hp.

Or should I just go with the Edelbrock 2516 marine intake manifold and 4 Barrel 600 cfm Eldelbrock carburator which should get me a 30 HP increase and better tourque right across the rev range?

Maybe a moderator or someone who has done a similar conversion could advise?

 

[scoflaw]

HP is not low end torque, horsepower comes in at higher rpm's. So a 4 barrel won't do that. Another prop could work for you, like a 4 blade

 

[Davidsgara]

Yes agreed.
I,m currently running a Turning Point 4 blade SS prop. Wouldn't the Edelbrock Performer give more low end torque being a high rise manifold ?

 

[scoflaw]

Short answer, no. I've owned 3 5.0's and I can say they are slugs. They do alright but....sounds like you want more, I would'nt waste another dollar on it trying to make it quicker. Won't happen.

If it was good enough when it was new, maybe it's just getting tired. Being carbed, a 350 would drop right in using the same harness and accesories

 

[Davidsgara]

The 5.0 only has 130 hrs and good compression so Im sure its not "tired".

It would be nice to drop in a 350...but in the short term Im sure a change from stock 2 barrel carb and manifold to a 4 barrel Edelbrock carb and manifold should wake it up a bit......

So I'm still debating weather to get the second hand EFI set-up from ebay or go with the manifold and carb upgrade????

 

[Lou C]

I vote carb. EFI in boats is great when everything is new and corrosion has not started in on the connectors, etc. I have not tried putting a 4bbl on a V8 that came with a 2bbl but I can tell you that my old 4.3 with the 4bbl Quadrajet really feels a surge of power over about 3800 rpm or so when the secondaries (huge on the Quadrajet) open up. The issue will be that you will have to experiment to get the jets and metering rods correct.

 

[Davidsgara]

Yeah a new Carb and manifold over a second hand used EFI seems the logical choice to me as well.Thanks

 

[Davidsgara]

Make sure that u have the clearance between top of air breather (with high rise manifold added) and hatch.

Thanks I checked and have got about 5 inches at the moment between top of flame arrestor and underside of engine hatch

 

[Davidsgara]

I vote carb. EFI in boats is great when everything is new and corrosion has not started in on the connectors, etc. I have not tried putting a 4bbl on a V8 that came with a 2bbl but I can tell you that my old 4.3 with the 4bbl Quadrajet really feels a surge of power over about 3800 rpm or so when the secondaries (huge on the Quadrajet) open up. The issue will be that you will have to experiment to get the jets and metering rods correct.

I have been looking a few forum reviews and they are all saying that there is noticeable increase in power going to the 4bbl from the stock 2bbl Mercarb and manifold. Hopefully the Edelbrock 1409 won't need too much tweeking.....

 

[Scott Danforth]

ad a 2" carb spacer and you pick up some low to mid range as well.

 

[Davidsgara]

ad a 2" carb spacer and you pick up some low to mid range as well.

Sound like a plan