No Coast

I've been following your other thread regarding your engine performance. The problems you are having have nothing to do with the series of MEFI computer. Changing to a 4 will likely make the engine not run at all because you cannot find a supporting tune to flash into the computer. The computer is only as good as the tune in it. You need to go back to basics, perform a leak down test on the engine to verify mechanical condition, install a fuel pressure gauge while running, install wideband sensors, and get a scan tool to read all sensors and look at parameters. Today's engines are not tuned with tools, they are tuned with computers. This is all costly things to buy just to evaluate running condition but they are what you need to verify proper performance. Mechanics charge money for the service because they have the tools to get the information. If your performance is acceptable and especially if you are selling the thing soon I'd recommend you leave it alone and stop messing with it. The hot cam you are considering will hurt the performance more since the WOT rpm is 4000 rpm. A custom tune is the only thing that may help you get the last bit of efficiency out of your engine, there are sources for that, they will install all the things I described to properly tune your engine. The expected gains probably won't justify the cost of doing it. This is all just my opinion, I wish you luck in your learning experience.

No Coast

Fuel consumption is mostly controlled by input from manifold absolute pressure sensor, Coolant temp sensor, intake air temp sensor, and fuel pressure. The timing is controlled by the computer. The computer uses all these inputs to produce injector pulse width or amount of fuel per pulse. The coolant sensor for your gauge on the dash is different from the computer sensor. You must have a scan tool to see the computer coolant sensor real time.

1 2 NV

I realize how EFI works. I've done tuning of my old racecar in the past.

I also built a 383 for the same boat that I pulled out because I decided to sell the boat. 383, forged everything, Afr vortec heads, comp xm 276, stealthram topped with a Holley hp FI system. It ran poorly though because I shifted the rpm range too high. I think the low compression also had a lot to do with it.
It kind of pissed me off because I had help from an engine builder that knew my impeller and boating demands. It fell well short of what we were expecting.

So back to the 350 in question. Its got a Fp guage, new plugs, wires, cap, rotor and oil. I recently swapped out the coolant sensor for the ecu. Time will tell. I'm patient and I'll keep sorting through this.

1 2 NV

Here we are. Ended up keeping the boat. The boat still runs fine.
However, it's still burning fuel like crazy. I've swept all sensors and all appear normal with my methods. I was hoping that temperature sensor swap was the culprit. Today after starting it up during warmup you could see and smell the cloud of black smoke.
I now wonder if it's the program in the ECU. Maybe Marine power installed the wrong program if they even did anything to it.

sutphen 30

Sounds like you need a retune , ,where are you located?

BUP

iTrader: (9)

ECM calibrations are app and marine manufacturer specific only - plus for stock built engines thru the OEM's only. They do not mix and match period unless one recals per that specific engine

Trash

What is your main problem? Rich idle? Do you have AFR readings other than black smoke and smell? I would NOT swap MEFIs at this point. Do you have access to MEFI burn to read the bin file?

1 2 NV

I do not have O2 plates built in. I know I ran 40 miles each way and burned 60 gallons. My 383 didn't burn that.

1 2 NV

I forgot to answer your question trash. I do not have mefiburn to look at the bin file. I sure wish I could figure out if it's a sensor problem or a ECU problem. At this point I'm pretty close to throwing my 383 back in there and running it. I want to bump the CR up before doing that though.

jwurl