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Contributor

Re: 3126 420HP Boost Pressure and EGT

Hi Dave.

Do you have this data for a 3126 420HP serial No.8NM03713?

Thanks in advance

Marcos

Super Contributor

Re: 3126 420HP Boost Pressure and EGT

Prop demand data for 385HP 3126 RPM BHP FUEL RATE GPH INTAKE MFLD P IN-HG EXH MFLD TEMP DEG F EXH STACK TEMP DEG F 2,800 385 19.47 59.97 1,041.62 703.58 2,600 308 14.98 47.5 913.1 639.86 2,520 281 13.58 41.9 887.72 636.62 2,400 242 11.73 33.55 863.78 640.76 2,200 187 9.11 21.56 840.38 650.3 2,100 162 8 16.73 824.36 647.6 2,000 140 7.03 12.73 806.18 638.06 1,800 102 5.31 6.96 738.5 585.5 1,680 83 4.41 4.62 685.76 541.04 1,600 72 3.88 3.41 645.44 510.08 1,400 48 2.77 0.92 550.76 433.58 1,200 30 1.9 0.36 454.1 360.32 1,120 25 1.61 0.47 417.92 331.7
Contributor

Re: 3126 420HP Boost Pressure and EGT

Dave:

 

Mine are actually 385HP....

 

Thanks in advance...

Super Contributor

Re: 3126 420HP Boost Pressure and EGT

Are your engines rated at 420HP or 350HP??
Contributor

Re: 3126 420HP Boost Pressure and EGT

I Installed my EGT and Boost Guages last weekend.    However, I haven't had a chance to really test things out well, but I hope to be able to run the boat next weekend and get some data.   I installed the EGT sensor in an existing 'plug' on the output side of the turbo.   So I guess that I am goind to be reading stack temps (is that correct?)

 

The motors have ~500 hours on them and run perfectly.   A little white smoke on startup (stbd only) that clears right up in seconds.  Operating temps are solid at ~180-185F.   I reach max  WOT of ~2850 fully loaded (Photo tach/digital tach confirmed).

 

Assuming my numbers are in the target ranges outlined by dave:

 

350HP

Stack temp (after turbo)        760F

Boost  pressure                       28 psi

 

I have a bunch of questions and I hope I'm not being too much of a PITA.

 

Are the numbers above max numbers at the rated 2800 RPMs or max cruise numbers at the rated 2400 RPMs?

 

If they are max WOT numbers, what should I expect at my typical 2300 RPM cruise?

 

How will I be able to best utilize this new information?  

 

How would I calculate load at varying RPM ranges?  

 

How can I best use this new helm info to maintain or monitor the health of the motors?

 

Any other useful information that I can derive from this info?

 

Thanks in advance for all info and replies and again, sorry for all the Q's.

Super Contributor

Re: 3126 420HP Boost Pressure and EGT

If your engines reach rated RPM plus 1-3%  (2830-2880) with boat at maximum weight,  then they are not overloaded. Engines should be run at 2400 RPM or less at cruise.

Contributor

Re: 3126 420HP Boost Pressure and EGT

Hi Dave and again thanks your info.

Have you any data on what should be the cruise exhaust manifold temperature, stack temp and boost pressure,  that is a condition for continuous operation without overloading the engines?

Contributor

Re: 3126 420HP Boost Pressure and EGT

Thanks for the your info.

Have you any figures for cruise conditions?

The 34 psi max boost pressure seem a bit high.

Super Contributor

Re: 3126 420HP Boost Pressure and EGT

Normal maximum temps and pressures:

 

420HP

Exhaust manifold temp       1140F

Stack temp (after turbo)        780F

Boost   pressure                      34 psi

 

 

350HP

Exhaust manifold temp      1065F

Stack temp (after turbo)        760F

Boost  pressure                       28 psi

Contributor

Re: 3126 420HP Boost Pressure and EGT

Hi JAAS

One of the engine serial No. is: 8NM03713  . The other one is the same series.

By the way the temperature measurement is better to take it before or after the turbo?

Thank you