2000 Mercury 150 EFI down two cylinders

[pancakes]

I'm chasing a problem on a 150 EFI, year 2000. Cylinders 2 & 4 are failing drop test though when boot is pulled while running, i do see a spark. When plugs are pulled, 2 & 4 are much cleaner than the rest. Like Brand new clean. 2 is cleanest with no sign of combustion whatsoever and 4 has very slight wet blackening on inside of gap surfaces only. Both 2 & 4 plugs seem to be wet with fuel. Other 4 plugs look normal.

A little background:
-compression is an even 125 on all cylinders
-injectors just serviced and all seals and o-rings replaced
-new'ish stator, trigger, regulator/rectefier(CDI)
-new main harness
-new plugs
-checked resistance at injector harness and i'm getting .8 ohms on the blue, yellow and white wires when checked against red. i know this is slightly out of spec but maybe it's my meter?
-switched CDMs, problem did not follow.
-new HP fuel Pump
-new pulse pump
-Fresh gas
-new water seperator
-rebuilt ECU by dennis hoffman in kentucky

I think that's it cant give up now!

I had the motor at a local shop in a non-run condition on account of a vacuum leak caused by incorrect re-assembly of induction manifold (by me). I missed the bottom corner of the induction manifold cover gasket and it was sucking a ton of air. they may have fooled with the timing to get it to run to try and find the leak. they didn't find it so i took the boat home and fixed it myself. They are understaffed / too busy and keep giving me the run around.

My question is, could the advanced/retarded timing be the cause of this type of misfire?

I don't have the tools to check and set timing.

thanks!

 

[racerone]

Put timing mark for EACH cylinder on the flywheel.-----Then check to see if each cylinder is firing at the correct time.

 

[pancakes]

I don't think i can get into setting up timing myself since i don't have acess to a timing light or the TPS harness.

Just wondering if this sounds like it COULD be a timing problem.

I can get the motor to run but those two cylinders are not firing.

 

[pancakes]

Since two of the plugs are so clean, i worry that the i'm getting water in those two cylinders. Would it be possible to have good compression AND water in combustion chamber?

 

[racerone]

Sure----An exhaust plate gasket can leak.-----But check that all wires are in the correct place going to the coils.-------Or switch 2 and 4 and see what happens.

 

[pancakes]

Great info, thank you. I was under the impression that good compression meant water could not get into the cylinder. I guess that would also account for the excessive oil sludge dumping out of the prop. i'm encouraged!

Good thought on the switched but the harness is marked and it's correct.

Is this the part i should be looking at?

 

[pancakes]

I went ahead and changed out the exhaust plate gasket and no dice. still no fire on #2 and #4. There did appear to be some water beading in the exhaust ports of those cylinders. I also noticed some scoring on the #2 piston. Could i still have good compression with a bad head gasket? scratching my head over here...and my pistons

 

[Faztbullet]

Pull the head!!!!

 

[pancakes]

hey guys, yep pulled the head and i can't REALLY tell if water is getting in through the O-ring gaskets by the look of them but maybe someone can...i'll replace all head seals on that side and see if i get an improvement. here's a shot of the removed head. you can see how the top two look really clean. you'll also see some water beads(bad pic) on the inside of the exhaust port. Also, check out the shot of the # 2 piston through the exhaust port which has some scoring. I'm not sure how catastrophic that is but i'll know when i get her all patched up.

 

[Dukedog]

2 is toast.. 4 not far behind.. get it fixed now or ya may end up with a complete pile a junk...

 

[Faztbullet]

Tis rebuild time...Who serviced injectors as 2 and 4 need to be looked at again?

 

[pancakes]

ugh, was afraid of that.

The injectors were serviced at a local shop. Does this look like fuel starvation? I've been assuming water infiltration into the head. Should i save the money and effort on the head gasket and skip right to the rebuild?

 

[Faztbullet]

Head gasket aint going to help the damage on piston.....pull it apart.

 

[pancakes]

ooof, yep.