2 barrel carb change to Throttle Body Injection

[Lakerider]

I have a 1997 Larson with a 4.3L
V6. It has a 2 barrel carb and I am wondering how hard it would be to change it to TBI. I have a 1995 4.3L with TBI in a chevy blazer. Just curious what would be involved and what kind of performance gains I would get from the change or would it be better to just change to a 4 barrel and skip the headache.

 

[1979checkmate]

Re: 2 barrel carb change to Throttle Body Injection

wrong forum.. belongs in i/o, not outboard. Could a mod please move it so Lakerider can get some feedback to his question.

 

[Bondo]

Re: 2 barrel carb change to Throttle Body Injection

I have a 1997 Larson with a 4.3L
V6. It has a 2 barrel carb and I am wondering how hard it would be to change it to TBI. I have a 1995 4.3L with TBI in a chevy blazer. Just curious what would be involved and what kind of performance gains I would get from the change or would it be better to just change to a 4 barrel and skip the headache.

Ayuh,... Pretty much Impossible....

It needs a computer, 'n all the sensors to run....

 

[Lakerider]

Re: 2 barrel carb change to Throttle Body Injection

New to this. Thought I put this post in the Other brands of I/O and inboard engines and outdrives.

 

[Lakerider]

Re: 2 barrel carb change to Throttle Body Injection

I have the complete vehicle. That is the blazer with computer and TBI
Can the computer not be used from the original vehicle for the swap?

 

[Bondo]

Re: 2 barrel carb change to Throttle Body Injection

I have the complete vehicle. That is the blazer with computer and TBI
Can the computer not be used from the original vehicle for the swap?

Nope, 'n most of the sensors are usless too...

 

[sschefer]

Re: 2 barrel carb change to Throttle Body Injection

Bond-o is right, the sensors are for a passenger vehicle with a very mild camshaft. The lift and duration of the cam in your marine engine is totally different and the majority of the sensor data would be useless. You could reprogram the chip for the marine cam but your performance gains would not be great enough to offset the work and cost.

A TBI system is not true fuel injection it's just a slightly better way to control the fuel/air ratio. A $25.00 vaccum gauge will probably bring a bigger payback.

 

[Lakerider]

Re: 2 barrel carb change to Throttle Body Injection

Thanks. That kind of what I thought about the cam and the fact it's not true injection.
I think I will go for the switch to a 4 barrel carb with vacuum secondary. I think i will get more horsepower better low end and still get good economy at cruising speed. Probably not as good as the computer control TBI. But I can't have my cake and eat it too.

 

[jeremyhuston]

Re: 2 barrel carb change to Throttle Body Injection

I just want to say I totally disagree. I think it would be simple and EASY. you would need the TBI intake from your vehicle along with the TBI unit. Installed in the TBI unit is the IAC, Throttle Position, and behind is the MAP. YOu would also grab the CTS (coolant temp. sensor). You would install, along with a new fuel pump capable of 30 gph @ 15 PSI. THis would be in line before your filter, return line simply back to your tank. You would also install the 4.3 distributor with the ICM in the distributor itself. This module has a 2 wire harness that goes to your coil. You would cut the end off the coil side and simply install to your coil for spark timing. You would leave the hot wire currently to coil and this would also still function with your shift interrupt. For the ECM you would simply use the GM harness modified of course. You will need to go into the ECM and modify a few items. I would be glad to help you acheive this. You will have to buy a chip hold (GP1 adapter from Moates.net) This is used to hold the parameters you are going to change (no vss, o2 sensor, egr, etc.) also, you will need to cut a piece of steel to block off EGR port. You will be running the system in whats called open loop. This means the system will not receive feedback via. 02 sensor. You have 2 forms of fuel trim Long term (BLM) and Short term (INT) As long as the engine is datalogged and is close you can set the VE tables close enough that running in open loop will be fine. and it would definately outperform a carb.. (no need for junk chokes that dont work, or accelerator pumps, blah blah.)

Obviously you would need to mount PCM/ECM in waterproof box (electrical box 12x12) PCM I would use preferably would be GM# 16197527. 93-95 blazer/s-10

Also, as for your donor engine. Even though the valve covers may say vortec. GM used standard heads until 96' which uses the CMFI style fuel injection (6 poppet valves centrally located) should be visually obvious. This means your intake should work fine on your engine.

 

[sdowney717]

Re: 2 barrel carb change to Throttle Body Injection

even if you get it running, is it a legal system?
I remember on another forum, people said you cant return fuel to the tank for a gasoline EFI system running in a boat which was designed for a car.

 

[sdowney717]

Re: 2 barrel carb change to Throttle Body Injection

http://www.boatdesign.net/forums/sterndrives/carby-fuel-injection-17438-3.html

read post #34

 

[jeremyhuston]

Re: 2 barrel carb change to Throttle Body Injection

2 points. Any fuel injection is going to have a return fuel line. Second. Affordable fuel injection has tell same kit I just described for sale. They haven't been sued.... said they've done thousands

 

[Kaplooi]

Re: 2 barrel carb change to Throttle Body Injection

Doesn't a '95 TBI have the 12 bolt intake manifold and '96 and beyond 4.3s have the 8 bolt Vortec manifold? Unless you're considering swapping heads I'm not sure your manifolds are compatible unless a TBI throttle body mates up perfectly to a 2 barrel intake manifold with places for all the sensors. Also even with the right bolt pattern the thermostat housing is clocked off to the side on automotive manifolds where the marine t-stat housing needs to go on straight. Edelbrock makes performance manifolds that work for either marine or automotive because they have holes drilled for both orientations but then you might have aluminum intake on iron heads corrosion issues in a marine setup. With a 97 4.3 you should be considering multi-port EFI as the only desirable conversion, IMO. But piecing that together 'legally' with Mercruiser parts would be hugely expensive even for used components. But then even a 'legalish' setup would require a donor vehicle that's at least 96 or later. The 4 barrel option is your best bang for the buck upgrade in terms of increasing HP.

 

[jeremyhuston]

Re: 2 barrel carb change to Throttle Body Injection

You are correct about the intake bolt patterns.. BUT just because his boat is a 97 doesn't mean that merc stuck a 97' GM engine in it. I wouldnt be surprised at all to find that his engine was pre-vortec heads. That being said he can junkyard a tbi intake that bolts right up. If not theres 2 options, Make/buy an adapter or buy a $300 GM tbi intake to vortec heads... OR i forgot you can actually weld and redrill the intake but that seems like a lot of work and would be the lesser idea in my mind.

 

[jeremyhuston]

Re: 2 barrel carb change to Throttle Body Injection

Also, just to make sure we are on the same page.. for ME.. 96' up would be undesirable. I am able to program OBDI and the 96+ fuel injection system would be pointless due to the fact I couldnt program my own chips. Not saying it would be unusable.. just to me. That is why I would prefer the TBI fuel injection system. Plus I feel it is very solid its essentially a computer controlled carburetor that is dependable. I use this same setup in my rock crawler and wifes jeep. NEVER had a problem, I watch so many guys fight carburetors to no avail.

 

[Bamaman1]

Re: 2 barrel carb change to Throttle Body Injection

Edelbrock and Holley make Throttle Body Injection kits, including wiring, etc. There are some other sources of add on TBI kits to replace carbs. If you Google them, you may find a universal kit that might be suitable for marine use. Most of the kits are for Chevy and Ford V8's, however.

I saw them install one on SpeedTV.com one Saturday.

 

[Lakerider]

Re: 2 barrel carb change to Throttle Body Injection

Thanks for all the inputs And answers. All the programming and stuff seems like a lot more than I want to try just for a pleasure boat I am still thinking a 4 barrel will be my best option and the easiest switch.

 

[John_S]

Re: 2 barrel carb change to Throttle Body Injection

All the programming and stuff seems like a lot more than I want to try just for a pleasure boat I am still thinking a 4 barrel will be my best option and the easiest switch.

I would agree with that. A Edelbrock 1409 w/4.3L kit would be a good carb choice.