Laser 220 XRI EFI lacks power and missing. Ignition problems?

I'm still fighting my 220hp Merc and I feel like I'm tried every trick in my book with no success.

So far the following things been done:

New spakplug
Watersprayed ignition components
Ohm tested sparkplug wires
Put on extra ground cable to the ECU
Checked for corroded ground cables
Got the injectors tested, no one is leeking
Cleaned throttlehousing
Cleaned all fuel filters
Compression test
Checked vaacuum hoses

Well, I think that is all, I don't know how to proceed in the troubleshooting. It still runs uneven with a fluctuating tachometer.

How should I proceed? All input is welcome since I'm really on my own in this since there isn't a outboard mechanic that got a clue about these engines in Gotheburg, Sweden..

Do you actually hear the engine rpm fluctuating? Is this an idle issue or high speed issue? Sometimes tachs lie.

Well, it is hard to actually hear the engine missing, i think it is more like it is shaking a bit. Perhaps these V6 engines doesen't run so smoothly? I do not have any engine of this size to refer to. In my world engines with more cylinder run more vibration free than engines with less cylinders.

Perhaps it is the tachometer that is fooling me but in idle (neutral) it is fluctuates about 150-200rpms constantly. If I hold the accelerator pedal steady at about 1300rpms in neutral the same thing happens, the needle moves up and down about 200rpms

This is the case aswell in gear, travelling at idle or in low rpms, the ta h needle travels up and down slightly.

Up in plane this is however gone, at 3000rpms and up the needle is rock steady and no vibrations is to be felt. Mashing the throttle to the bottom I got a maximum rpm of 5000. I think It should be able to rev atleast another 900-1000 rpms,

This is the engine I'm hassle with. I guess the powerhead been swapped sometime over the years since I think the engine is from 87 or 88 and the powerhead seems to me from 94.

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Did you check fuel pressure?
How's the lower unit oil? Prop shaft not bent? Spline on the driveshaft okay?
Just throwing this at you in case it's not powerhead related. A binding bearing can cause a vibration also

If its a 2.5 powerhead it wont run worth a chit with 2.4 fuel system....fuel mapping off.

Fuelpressure is one of the things that I havn't checked yet.

I don't think the lower unit is damaged in any way, the exterior is without a scratch and the prop spins fine in neutral.

faztbullet said:

If its a 2.5 powerhead it wont run worth a chit with 2.4 fuel system....fuel mapping off.

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Can the powerhead be a 2,5 if it is from 1994? There is a stamp in what looks like a freezeplug on top of the powerhead. It says "200".

Did some more digging into the engine. I found a cracked ignition coil, I'm not sure if it do anthing to the performance of the coil. Anyway I cleaned everything and removed som rust dom the little stainless conductor.

https://imgshare.io/image/7FNN5
https://imgshare.io/image/7DfsQ
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I found a little freezeplug on top of the powerhead, 200 should probably mean 200hp, but it doesen't say anything weather it is 2,4 or 2,5 liter.