Briggs 30hp professional bogs down

Just need to get a few things clear
1) are you running with the throttle wide open all the time
2) are to trying to mow 12 " while traveling at full speed on the sticks ?

I regularly mow 3' yes foot tall grass with a old 8 Hp without any problems other than deck choke requiring me to reverse regularly to clear the discharge chute.
However this has to be done at a crawl, which is easy on this mower as it has a 7000 series Peerless box but even then I have to slip the clutch a little in the reeds & Tussock grass areas.

Unless you are doing a finish cut of 1/2" or less. full speed on the sticks is for getting to where you want to mow, not mowing.
Next is the blade , high lift blades can gobble up near twice the Hp as strait blades.

The engine is just one side of the story.
What is it sitting on ?
How big is the deck,
What blades are you running\
Do the spindles have spacers under the blades to change the blade height inside the deck ?
Do you have bagger on it, a restrictive discharge chute, no chute .
Lots of posts here from owners who had to open out the discharge chutes on bigger decks because the hole was so small it kept too much grass under the deck.

hi bertsmobile1 and thanks again for the reply. i do not mow the grass that high at full speed but i do always run the throttle at full rpm. rpm gauge itself shows 3640/3700 with pto on but it does drop when blades contact grass unless i run at half speed or less. i do currently have high lift blades on and did not know that would rob hp. thanks for that tip. the deck itself is 54" and i have always noticed an issue with grass buildup underneath. i do not run any type of catch system just straight discharge with no chute but i do routinely have to stop and clean deck buildup. no spacers on spindles. as far as what the engine is sitting on the mower itself i have read weighs close to 1200/1300 lbs. built like a tank. I've wondered in the past if its just to much weight for the motor.

If the chute is clogging up then the volume of grass is overwhelming the deck and that means you are travelling too fast for the amount of grass you are cutting.
Keeping a couple of pounds of grass in the air costs a lot of power.
So it sounds like an operator problem & not a mower one.
I cut a verg about 1 mile long which is full of tuffting grasses, reeds, blackberries, morning glory, potato vine ,lantana & when it rains 1000's of gum tree saplings.
I try to mow this at least monthly .
In winter, no problems but in summer it is at speeds that has snails flying past and even then , much backing up to clear the chute which like yours has no cover.
There is only so much a mowing deck can do.
If you have no option than to cut regularly when the grass is 12" or better then you might need different blades or a different mower all together.
It sounds like your governor is working as it should opening up the throttle when you put a load on the engine.
3600 rpm is the high IDLE, ie the speed the engine does with no load on it.
Dropping 10% when under load is normal running.
So if for instance your mower drops to 3000 under heavy load and maintains that 3000 rpm or moves between 3000 and 3600 then the system is working as it should.
If OTOH it hits the grass and the revs drop and continue to drop then the engine is under too much load, like trying to drive a fully loaded car up a hill towing a heavy trailer in top gear.

Gators tend to handle heavy cutting loads better than most standard blades if for no other reason than they weigh twice as much so have more inertia.

Most residential mowers are "finish" mowers, designed to cut no more than 3" off the top of a well maintained lawn.
Commercial mowers are a bit between finish & rough cut and will do an acceptable job on grass that is a foot tall.
After that you are looking at rough cut or slashers.

Ten years ago or so mower makers offered rough cut, finish cut, & bagging decks .
Now days some of the commercial decks will have removable bafels to convert it from one use to another.
However most decks are universal, meaning mediocre at strait cutting , mediocre at bagging , mediocre at rough cutting.

tony2 said:

hi bertsmobile1 and thanks again for the reply. i do not mow the grass that high at full speed but i do always run the throttle at full rpm. rpm gauge itself shows 3640/3700 with pto on but it does drop when blades contact grass unless i run at half speed or less. i do currently have high lift blades on and did not know that would rob hp. thanks for that tip. the deck itself is 54" and i have always noticed an issue with grass buildup underneath. i do not run any type of catch system just straight discharge with no chute but i do routinely have to stop and clean deck buildup. no spacers on spindles. as far as what the engine is sitting on the mower itself i have read weighs close to 1200/1300 lbs. built like a tank. I've wondered in the past if its just to much weight for the motor.

Click to expand...

Let me relate a story that occurred to me, I sold a commercial mowing customer a set of extra high lift blades for his 61" Scag, thinking that it would help grass discharge because of the extra air flow. What happened in reality was the extra lift caused it to pack the grass under the deck and not discharge it. Clogged the deck in the first 10 feet of mowing and had to stop and clean out the deck. This customer always used high lift blades, but the extra high lift caused a situation compared to mulching blades mowing wet grass and sticking to the deck

All I know is I've had multiple different finish mowers over the years. From garden tractors, too diesel tractor mounted finish mowers (3 point mounted and belly mowers), residential zero turn and commercial zero turn, Etc. and none of them do well trying to mow 8-12" grass.
Its a finish mower.
For deeper grass I use the brush hog.

thanks for the help guys. it would seem a consensus of information suggests mowing frequency(which my company may not approve of:laughing and a blade change may be in order. i will try both. it is a commercial outlaw series 54" deck, any suggestions on the lowest lift type blades?