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Good point. You can also do the same by pulling the outdrive. For my boat's config with the Alpha Gen 2's, that's the easier route. Those elbows can be a real bugger...One thing that CAN happen in the exhaust that isn't readily visible, is there could possibly be an old flapper that fell apart (usually from an overheat or from a while ago) and fell into the exhaust "Y". They can be in there a long time before being noticed. This I have seen more than once on other boats. An old flapper down there can / will block the exhaust and cause problems, including possibly eating a hole through the aluminum "Y" pipe and causing a water leak. Easy to check, Take off the riser and the pipe elbow after it and look down there with a cheap borescope.
I drained the gas by disconnecting the fuel line at the mechanical pump from the tank and attaching the hand vacuum pump I use for oil changes and spent the better part of a day pumping and pouring into red cans until the boats tank was empty. Put the fuel in my truck to dispose of it. Truck runs fine on it so fuel quality doesn’t seem to be an issue. The fuel I added a month or so ago was fresh from the station and non-ethanol. Fuel filter/water separator was then changed. Fuel pressure is holding at 37 psi at the rail even under load when it’s acting up. The new fuel injectors I got were from eBay and I paid $300 to have them and the old ones tested. Obviously the guy who tested them didn’t do it right. The SELOC manual said ohm test the injectors and if they are good they will show 12 ohms +/- .4. The old injectors all tested exactly at 12 and the new ones tested anything but. I tested both banks wiring with a test light and both banks appear to be functioning properly.
Scofflaw has a good point. Why start over . Many more advantages to fuel injection than carburation, period
I feel the pain of the op but this thread will go to nowhere i guess.
Money and parts were thrown on this engine by shooting in the dark - in an amount that you easily would get a certified mechanic paid , including travel or hauling in the boat to diagnose and fix the real problem .
Now money is spent for nothing and we hear 'amazing' new options to convert an mpi to a carb . Sweet .
Of course nobody here can say what the correct main and idle jets would be , how an mpi designed head / combustion chamber would react to a carb , what cfm carb .... and much much more . How can we ?
Dump another fortune to find out it still does not run since the idea is as smart as trying to convert an evinrude e-tech outboard to carbs .
If ( and how should it be possible by a forum ) you do not verify if :
-the head change was correctly done
-the timing is fully correct
-the ecu is ok
-the injectors are the correct type
-the injectors are verified ok
-the harness of the injectors is ok and installed correctly
There are so many variables what or what combination of different things could be wrong that you can happily entertain the forum but you will go to nowhere.
I,m scratching my head what sane person changes e.g the heads at all if the engine starts and idles fine , compression is even and tolerable ... ?????
You need to go logical step for step or pay the mechanic before your boat is a total loss...
I'd lik I am not haphazardly taking shots in the dark and replacing random expensive parts.
So far I’ve replaced the cylinder heads, exhaust manifolds, the spark plugs, spark plug wires, cap, rotor, distributor, ignition coil, ignition module, air temp sensor, MAP sensor, IAC, throttle position sensor, mechanical fuel pump, the electric pump in the vapor separator tank, the alternator, raw water impeller and housing , the heat exchangers, thermostat and housing, engine temp sender, oil pressure sender, the entire outdrive, and repaired or replaced wiring.
I'd like to reply to two things. First, I like to think I am smarter than your average bear when it comes to things mechanical. I have tools, training, and years of experience to competently perform basic maintenance and repair, as well as some complicated repair as well. I can cite all my experience if needed but it is quite a bit and I'd prefer not to. I simply don't work as an automotive mechanic anymore because I wasn't making enough money and enjoy things like eating, not being homeless, and occasionally being able to get on a boat and enjoy some time on the water. I also have the correct SELOC repair manual for my engine and posses the ability to read. I am not haphazardly taking shots in the dark and replacing random expensive parts. I perform the diagnostics prior and determine a fault in the part and then replace it but as of yet the main problem with the engine still won't remedy and all the diagnostics I perform currently tell me nothing should be wrong, but it very obviously does have something wrong. For the sake of brevity I try not to type every step of everything I've done. Its far easier and less time consuming for me to list simply what I did so its not suggested repeatedly that doing what was already done as a solution. Secondly, The carburetor modification. This would only be an option if I were to just give up and build a whole new engine. To just do a conversion of the existing block it would cost me approximately $3000.00 in parts to get everything it would need. The problem then is I would have a Frankenboat that no manual could ever help me to repair. If I'm going to redesign the wheel I'd much rather repower the thing with a diesel engine. I know a few guys where I could get a decent one for about the same price as building a whole new merc motor. I just don't want to do that, I'd rather keep it original.
Nascar went fuel injection in 2012....so. He's bought way too many fuel injected parts now to go back to Fred Flinstone era. I like my carbed old school cars and they run perfect but so do my last 5 fuel injected boats.