Engine Stutter/Bog From 2k-3k RPM

[FatPelican]

Sooo,

My 5.7 Mercruiser was "newly installed" by the owner when I bought it. The newly installed component was the Kodiak Marine 350 block, and everything else I assume was taken from his old engine. The install is very sloppy and has led me to a bunch of unrelated to this issue problems (pot puller ground disconnected, wash down pump wires corroded, engine tilt relays bad, my favorite being the complete lack of power steering pump cooler). Every since I have had it in the water, it has always had this stutter/bog from around 2-3k rpm. The engine idles fine, and after I get passed the bog, it runs great.

What I've done:

I checked my codes today using the wire and multimeter method and the only code I have is 12.

Replaced fuel filter and drained water separator.

Checked fuel pressure.

Ohmed injectors.

Replaced MAP sensor.

Tested fuel pressure regulator.

Checked timing, its close to what I think it should be. 8 BFDC if I'm correct.

Spark Arrestor is CLEAN.

Ran over 300 gallons through it, so "iTs nOt BaD gAS."

I DO NOT HAVE THE BOG PROBLEM ON THE TRAILER. ALL RPM RANGES WORK AS ADVERTISED.

Anybody have any ideas??? I've been running it and will continue run it, it would just really be nice to have that RPM range without bogging down and having the motor run like crap. I, as well as all my mechanic friends are at a loss.

Side note, what cruise RPM's should this motor be running?

93 Bayliner 2859 with a Bravo II if that matters.

 

[alldodge]

There are several different EFI motors, do you know what the original serial number of the motor is?

 

[FatPelican]

There are several different EFI motors, do you know what the original serial number of the motor is?

I don't, the only numbers I can find are the new Kodiak numbers. The original motor was a 7.4, I do know that. He switched to a 350 block for fuel economy I guess.

 

[alldodge]

I don't, the only numbers I can find are the new Kodiak numbers. The original motor was a 7.4, I do know that. He switched to a 350 block for fuel economy I guess.

OH boy, this does not sound good and I sure hope there are better things ahead

It use to have a 7.4 and now has a 5.7
Was the stuff from the 7.4 (injectors, ECM, other) used on the 5.7???

 

[FatPelican]

OH boy, this does not sound good and I sure hope there are better things ahead

It use to have a 7.4 and now has a 5.7
Was the stuff from the 7.4 (injectors, ECM, other) used on the 5.7???

Ha, well it can't get any worse. This boat "ran great" and had "50 hours on the new engine". I find it hard to believe he ran it 50 hours when the trim tabs weren't even hooked up to power, the engine tilt didn't work, and his shrimp pot puller wasn't grounded. Oh, and his battery charger wasn't hooked up either. Did I mention I had to get towed from 70 miles out?

This was my first boat and I let my excitement get the best of me, looking back now I would have looked at his rats nest of a wiring job and bought a different boat. The boat is getting new electronics and completely new wiring this winter, but that might not fix my stutter issue.

To answer your question, I have no idea. I'm to green to know the difference in all the accompanying parts, but I'm quickly learning how to solve problems. I'm an aircraft mechanic by trade, so this boat stuff is a little bit of a learning curve.

 

[alldodge]

Dang 70 mile tow

If the ECM was on a 7.4 and not reprogrammed then it will be supply to much fuel, it will run rich always

What year is the boat?