355 Mercury 300 promax problem! EGT TEMP HIGH!

**MaDneSS** · 08-15-2009, 09:37 AM

The egt on the left bank is reading alot less than the right bank,
for example when cruizing at say 4500-5000 rpm the egts read 600 degrees and 1100 degrees!

We have the remote right/lean part that replaces the air temp sensor and have tried both ends of the scale on that but cant seem to make an improovement!

please help!!

engine is a 300 promax with mad efi intake (3 hole on) 62cc heads, mad efi tuner, recurved ECU,simon drystack

**Da Bull** · 08-15-2009, 10:00 AM

What happens at Wide open throttle?

DB

**MaDneSS** · 08-15-2009, 10:13 AM

the temps even out a little but havent seen them closer than about 250-300 degrees.
I think it should be pulling harder aswel

**Stitch King** · 08-15-2009, 09:14 PM

I believe 300 promax has the bleed system only on one side of the motor. Just a guess but that may have something to do with making it rich/lean on one side or the other.

Talk to Simon. He's added bleeds to the side that has them missing to balance out the motor.

**MaDneSS** · 08-16-2009, 06:35 AM

Stich King,
Do you think the standard 39 psi fuel regulator from the 260 efi will be okay?
Im worried that its not getting enough fuel?
I feel its not pulling as hard as it should be.

**Stitch King** · 08-16-2009, 08:34 AM

Not sure of the specs of that regulator. Do you know?

I know that the factory regulator on the 3.0 liter is 38 at idle and 43.5 at anything above.

If you dont have 43.5 above idle you are not getting enough fuel.

My 3.0 actually liked 50 psi for the top end and mid. However, it would gag it at idle when I still had the merc boxes on it.

Do you have the MAD EFI fuel knob?

Do you know what your timing curve is in the Ign box?

**MaDneSS** · 08-17-2009, 03:18 AM

Hi,
The Regulator is the 'Gold' 2.5 efi one which i think it 39 psi!
I read in the manual that the promax standard one was 36 @ idle and 39 psi usually thats why i chose this one?

No idea what timing curve got put on, is there any way to find out?

Yep have the mad efi fuel nob,
Cheers

**STV_Keith** · 08-17-2009, 01:34 PM

Could also call Kevin at R&R Prop...he has run pyro's in 300PM's and 300x's. 702-564-7502.

**Stitch King** · 08-17-2009, 01:54 PM

Certainly you need more fuel pressure. Your injectors are calibrated to be at 43.5 psi.

Start there, then run egt temps again.

**MaDneSS** · 08-24-2009, 11:09 AM

Right results of running the stock 300 promax regualtor!!
cruizing at 3500rpm revs egt temps are 600 & 1000!!
when accelerating hard they level out a bit.

Also at about 1500 - 2000 rpm (when driving off plane, against the tide) there is loads of smoke! and ideas why this is and is there any way to stop this happening?
running 40:1 mercury premium plus oil.

**MaDneSS** · 09-22-2009, 04:43 AM

Ttttt

**PanRonnie** · 09-22-2009, 05:56 AM

one cilinder running rich (injector problem )
or no ignition on a cilinder
assumed you already checked compression
if this is not a 300X then it can,t be the injector driver because they do left and right at the same time one driver

**MaDneSS** · 10-09-2009, 05:34 AM

Had the injectors done now! all have been matched, They were pretty good only a few CC's off prior to cleaning,
Any other suggestions

Cheers

**Markus** · 10-09-2009, 06:40 AM

If all cylinders are getting enough fuel, check:

1. No spark on 1 cylinder

2. Water leak

Are the plugs too wet or too dry on the cold side?

**MaDneSS** · 10-09-2009, 07:21 AM

Plugs were all too rich, with the righ bank being richer than the left,

It runs smoothly so i think that it is running on all 6 but will check any way,
Where would i check for a water leak?
Cheers

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