Brand New Mercury Reman 300XS (just out of break-in) Surging/Skipping on the Top End

**JOE54** · 08-12-2020, 04:08 PM

i think its going to rich if it was lean as few hrs on it sob would blew up ,just my humble opinion though , SAV do plugs look black ??????

**Savage** · 08-12-2020, 06:48 PM

Don thought that maybe the adapter plate gasket had failed and caused water to mix with the exhaust, so he asked me to check it out. I pressure tested the cooling system, with 40 PSI house well water, with the lower unit removed. The only water exiting the motor was at the tattle tale and out of the orifice hole between the end bells of the tuner. I also ran the motor for a couple of minutes and re-checked, but found no water coming out of the exhaust end bells, so the adapter plate gasket is fine.

JOE54 after taking a bath, lying on my back looking up at the tuner, with the water hose on, I just don't feel like pulling plugs again tonight. I'll check the plugs again tomorrow afternoon.

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**Savage** · 08-12-2020, 08:43 PM

Don stranger things have happened, but what are the chances, that one of the brand new #4 and #6 direct injectors is BAD again? Both direct injectors were in foil sealed bags from Mercury.

I can't believe I convinced myself to ask this question.......this is so far fetched. I'm almost out of options!

**lpugh** · 08-12-2020, 11:24 PM

I know your grasping, any chance off an exhaust leak (EGR unwanted) in to the cowl area, or cowl intake obstructions
Maybe a timing check at WOT to see if timing is being retarded by PCM for some reason
Diode/Stator test, can raise hell with the PCM
any sensor wires laying against coils or plug wires

**EuropeanAM** · 08-13-2020, 09:46 AM

Savage... not impossible, but pretty unlikely.

No sound blanket in the upper cowling, correct?

**Savage** · 08-13-2020, 11:07 AM

Originally Posted by EuropeanAM

Savage... not impossible, but pretty unlikely.

No sound blanket in the upper cowling, correct?

No I took the blanket out of the top when I heard about it falling down and cutting off the air supply.

**rvaha** · 08-13-2020, 06:23 PM

If you put on a lower pitch prop, does it still hit the wall at 5400rpm?

**EuropeanAM** · 08-13-2020, 06:36 PM

Originally Posted by rvaha

If you put on a lower pitch prop, does it still hit the wall at 5400rpm?

We should know the answer to that in a couple days.

**JOE54** · 08-13-2020, 08:58 PM

i need sleep

**EuropeanAM** · 08-14-2020, 09:02 AM

Originally Posted by JOE54

i need sleep

NO doubt. Some folks don't realize the things that keep us up at night!

**Savage** · 08-15-2020, 10:59 AM

So I removed the plenum and reeds, with the purpose of checking for loose reed screws, and I found this on the bottom of the cylinder bores.

Check out the sleeve alignment at the bottom of the bore >>>>

The sleeves in the cylinders do not align with the block, or the pistons.

Cylinder #2

Cylinder #4

Cylinder #6

Cylinder #1 Alignment is better on the starboard side.

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Cylinder #3