Re: Measuring Engine Load

Hi Manieto


Sorry but some one aske for serie nr.


If we have serie nr we can see engine specification this will tel us fuel rate.

what you can use to compare to see what HP/ltr.

so if you know ltr or gal you have used 1 hour you can see de HP.


also boost MAP can give you indication of +/-engine load.


So top up your fuel tank.

Run Engine one hour full load or 1/2 hour. 

top up tank and you know !


know the liters you need to top up your tank


your engine hosepower perform

New member BHB
New member

Re: Measuring Engine Load

What is the process fuel transorpump.

Re: Measuring Engine Load

LEBV 4830, Marine Analyst Service Handbook. I have the latest copy of this book. Very useful to analyze boat performance. Actually, Engine ECM use that formula to determine engine load factor. You can try to calculate on your own engine.
Super Contributor

Re: Measuring Engine Load

Fuel rate by itself is not always accurate in determing engine power output, CAT and the dealer organization spent a lot of time and effort developing the Marine PAR program, I think many have assumed since the advent of electronic engines the PAR testing is no longer relevant, in my experience this is a bad assumption.  Many factors affect the horspower production in a marine propulsion application.


CAT has a published Guide (or used ), a green handbook for Marine Performance Analysis, I'm trveling and don't have my old files but maybe a dealer or CAT person would be kind enough to post the literature number of the handbook and tell us if it's still available.


Hey CAT folks, here is your opportunity to trot out Marine PAR again, how about some up to date info?


Re: Measuring Engine Load

Can another variable, like the engine boost pressure be used in this formula?

Using boost pressure as variable, for upper RPM end (2500 rpm and up) the formula will gives the exact same value (using the "Prop Demand Data" for boost pressure and fuel rate values) but what I don´t  know if under certain conditions this values will give totally different results.

For the lower end, from 2400 down to 2000 you will get a difference of 5% to 10% in the engine load factor when using fuel rate and boost pressure in the formula.

I ask this because is much easier to get a boost pressure gauge than a flow meter and at the end that matters it will apparently give the same value.



Re: Measuring Engine Load

The formula to calculate Engine Load Factor in mechanical engine:

Actual Fuel Rate / Maximum fuel rate X 100 %


Please send me the serial number of your 3126 engine, then i will find specification of it's maximum fuel rate.


Electronic engine use this formula:

Fuel Position / Rated Fuel Limit X 100 %


MPD (or another monitoring system) will show load factor of engine by this formula. Be aware, it can blame you. Since the ECM use injection duration to assume "fuel position", the engine load factor may vary between MPD and actual load.

Cat Dealer

Re: Measuring Engine Load

On the 3126 Mechanical which this probably is you need to hook up a fuel flow meter and check the prop demand curve to calculate load.  On the electronic engine the Cat EMS or MPD panels will tell you.


Re: Measuring Engine Load

[ Edited ]

syahrir: Would you mind sharing the formula to calculate load here for the mechanical 3126 motors?


Re: Measuring Engine Load

May i know the types of your engine, electronic or fully mechanical? Since the electronic engine using Injection Duration as parameter to measure Engine Load Factor, we can use this methode as well in mechanical engine. The only parameter you need to calculate engine load factor is Fuel Burn Rate. Please email me at for further information...


Measuring Engine Load

Hi everyone

My boat engines are 420 hp 3126 and I have no instruments to measure the engine load (% of full load).

Is there a practical way to know this very important variable using the available data (boost pressure, exhaust or stack temperature, engine RPM). When the electronic engines display this variable what is actually being measured?

Marcos Nieto