Can a Pump with max HP rating be used on a higher HP engine?

Right. You will have to have a governor on the engine to keep it from exceeding the maximum pump rpm as well as the pressure relief valve.

You need to consider very carefully the power and torque in your applications. If your grass cutting deck was to consume 20 HP to cut a given section of grass, there would be 20 HP remaining to propel the rig. But when your grass load is less, it might only consume 10 Hp for that section of grass. That would leave 30 HP remaining to power the hydrostatic drive. That much power could over power the hydrostatic trans, causing snapped shafts, or other broken parts in the hydrostatic drive unit.

I would play it safe, and design the entire drive system for the total power available from the engine. That way any power used to cut grass, will provide some cushion of reliability to your drive train.

Why don't you drive the grass cutting system by hydraulics as well. This would allow you to engage and disengage the cutting blades, as well as selecting the most desirable cutting speed to engine speed ratio.

Under normal conditions a properly governed ICE will output only the power consumed by the driven machines. The throttle will open and close to maintain the 2600 rpm.

It would be advisable to note the speed variation under load changes.

The pump power requirements then need to be analyzed in that speed range and geared down if necessary .

As said above pressure release valve is essential.

A mechanical failure in the pump will however pose a problem because the ICE will rise to the occasion and deliver that power. The pump supplier may claim that the excessive power caused the bearing to fail while the faulty bearing actually caused the excessive power.

Have you considered using a pump with better specs?

"As an example. Every auto engine does such under the hood.Look at all of the low HP rated things that the engine powers besides the auto!Alfred

Yes, even a Hydraulic Power Steering Pump that may require as little as 5 HP when assisting the steering process.

"Do not use a shearpin or whatever."

I strongly disagree!

In over 40 years of maintaining and repairing heavy & farm equipment,nuclear & diesel submarines,paper mills and chemical plants,I have experienced and repaired many simple to catastrophic equipment failures.Many if not most of the catastrophic failures could have been prevented by simple safety devices such as a "shear pin".As a "HAZMAT,HAZWOPER trained and certified emergency responder" for most of these years,I also put out the fires,secured the area,treated & decontaminated the wounded for transport and cleaned up the often hazardous materials,all before inspections and repairs could be started.Yes,machinery flying apart often does such things.

When rotating machinery fails or locks up,something has to give.Engineers and designers often ignore this simple fact of life.Parts often tear off and go flying.The United States Government,through OSHA has thousands of reports of injury,maiming,crippling and death that has been caused by such.

A simple "Shear PIN" used as a "final" safety device in case all else fails has saved much destruction and many lives.I have seen the results of installing them after repeated failures and destruction without them.A shear pin should never shear UNLESS all else has failed.Please think about this.Lives often depend on it!

A shear pin was and is used simply as a example.There are many proper safety devices for rotating machinery."Not using them if they are available has been ruled as willful and deliberate negligence".I was once told this by a USA OSHA inspector.

I once had a pump "Explode" within 3 feet of me.A piece flew close by my head and broke the steel railing on a Rail Road Tank Car behind me.This was not a rare thing with this pump.The designers and Engineers had decided that the "Guards" would contain it.They seldom did!

PLEASE! Use all proper safety devices with all rotating machinery.A life could well depend on it.Alfred

Horse Power Limiting hydraulic pumps allow big pumps on small engines ... I know most US hydraulics are in the dark ages like water plumbing.. but there are a few HP limiting pumps from Parker HY-30, Kawasaki K3VL, RHL PA etc. They are variable displacement and hence expensive. Basically you get max flow at low pressure and then the pump compenstates as pressure rises (power = flow x pressure roughly) until you get to max pressure when the pump can pull flow back to zero. All 3 are settable (ie flow pressure and HP). You might argue that the relief valve can be deleted.. but really it cannot and it should be set 2-500 psi higher than the pump max pressure so that you do not cook the oil by dumping energy over the relief valve.

Thanks for the input so far, this is most helpful. For me now the question is; how do you 'tap off' some power for a hydraulic pump, that has an input HP limit, form a more powerful source?

As noted by some responders, there are applications on large engines were small pumps use power from a more powerful source engine.

I agree with using a shear pin to prevent damage, bu there must be a way of using a little bit of power from a source

Mudguard

We use to build pumps in FLA for farmers using 2 chevy engines. One ran on gas the other pumped water lol . fab a connector plate for the out put shaft of an old straight shift transmission. Set it to 3rd or 4th gear and run it. install grease fittings and pump heavey gease thru the engine and add grease every 4 to 6 hours of use. the water leaking past the pistons of the pump engines kept it cool and hekp the grease mostly in place.