EFI Conversion

I'm looking for someone who may have converted a carbureted 454 Merc w/BIII to EFI. Engine is 1990 model. I see that Edelbrock makes the necessary kit to accomplish this, but apparently I need to do some serious mod to the water sleeve surrounding the exhaust in order to mount the O2 sensor. The Edelbrock technician, via email, sent a drawing and said that it's necessary to cut a relatively large hole in the water jacket, drill and tap into the exhaust for the O2 sensor to mount, then somehow weld a tube around the O2 sensor between the exhaust and the water sleeve thereby resealing the water jacket.

I was looking for improved fuel efficiency and a little better torque/horsepower to get up on plane, but these mods are a bit daunting to me--never was much for cutting holes into things that are supposed to contain liquids. I'd like to understand from someone who's been there how difficult this might be.

Thanks for any "lessons learned"

Re: EFI Conversion

I can't vouch for that system personally, but you can probably run without the O2 sensor. It helps to fine tune the amount of fuel. Without it, the computer will default to a slightly rich mixture. You want that in a boat anyhow. In a boat, a fat motor is a happy motor - a lean motor is a dead motor. You also need to make sure that the system is marine approved. There are different considerations for boat applications than automotive. For instance, automotive systems have a fuel return to the fuel tank. That's a USCG no-no in a boat. BIG no-no!

Re: EFI Conversion

Hmmm...an O2 sensor that works when wet! That I have not heard of before. Also believe that O2 sensors need to be at a lot higher temp than a marine exhaust runs at to work properly.

Edit: I reread your post and see how they wanted you to mount the O2 Sensor. It would require major modification of the riser and welding to cast metal of the riser. I would not attempt that.

There are aftermarket marine EFI available out there. They don't use O2 sensor so they essentually run open loop instead of closed loop. They are more like early auto fuel injection systems.

How many hours do you run your boat a year? I have a feeling you could buy a lot of fuel for the price of an EFI system. Not sure you would save in the long run.

Re: EFI Conversion

I agree with bruce, EFI may not be in your best interest. The fuel savings will be minimal and the power gains(over the carb) came primarily as a result of the intake manifold. Your best bet would be to shop around and get a higher performance manifold and keep the carb. Don't go crazy though, you want a manifold that builds power below 5000RPM, manifolds for higher RPM ranges will kill bottom end torque, thus killing hole shot and your cruising economy.

Re: EFI Conversion

Thanks, everyone! I'll enjoy the boat as is this season and then reconsider next year. I sort of suspected that maybe this was a lot of trouble ($) for not that much return.