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Hello all and thanks in advance for any help. I have a brigs and straton 30 hp professional that bogs down in tall grass. When mower was brand new it ran fine for about a week , then the issue started. Mower is now five years.
over the years of trying to fix this issue i have replaced stator, voltage regulator, checked valves, plugs , run non ethanol gas, checked clutch , wiring, changed belts checked blade housing bearings etc. i have been told that the engine i was sold on the unit is commercial but in actuality it is not. do not know if this is true but guy who told me was a mower mechanic at a high end shop. still, its a 30 hp motor and should cut 12 inch grass. any ideas on what the issue might be ? any suggestions are much appreciated

Had a mower like this come into the shop, just after I started, tried all sorts of things hen checked the engine by removing the plugs on each side.
Would not run on the left alone
Why
Because there was neither a piston nor rod in the left side.
Customer "though" it was a bit short in the "balls" department and they have been using it sans one piston since new for 5 years.

thanks for the reply bertsmobile1. unfortunately thats one of the many things I've tried in the past. motor runs fine when left or right plug is removed

12 inch grass might be the problem, have you tried raising the deck and making 2-3 passes or cutting more often, I assume those blades are sharp, are you mulching ..?? or discharging out the chute ?? Are you using any type of grass collector system ..??

If you get your engine Model, Serial, Family numbers you can call one of the replacement engines supply houses and the can probably give you all the info on your particular engine ... Pro series ( I think ) started 30 HP in 2009, and model numbers were 49M877 .. Commercial was 49M977 and some Pro 30 HP were 49G575 But don't hold me to it.

i run high lift blades some and mulch blades other times. no grass collection only straight discharge. the only way i can get it to cut is by making 2/3 passes. if i hit the grass at half speed in one pass height it bogs the mower to the point that it almost stalls out. this mower is all heavy duty commercial 54" outlaw series. blades extremely sharp. I've seen similar mowers with 24hp engines take taller grass with thick wet weeds run full speed without slowing or missing a blade of grass. I'm almost to the point after all this time of replacing with a 870cc kawasaki engine. the only reason i haven't yet is because i can't prove through process of elimination whether is engine or mechanical. just can't find anything on it that looks bad or doesn't work. i only use it on my yard and mower has only 130 hrs on it after 5 years. another reason i haven't swapped engines yet is i can't stand not knowing why this one won't perform.

tony2 said:

i run high lift blades some and mulch blades other times. no grass collection only straight discharge. the only way i can get it to cut is by making 2/3 passes. if i hit the grass at half speed in one pass height it bogs the mower to the point that it almost stalls out. this mower is all heavy duty commercial 54" outlaw series. blades extremely sharp. I've seen similar mowers with 24hp engines take taller grass with thick wet weeds run full speed without slowing or missing a blade of grass. I'm almost to the point after all this time of replacing with a 870cc kawasaki engine. the only reason i haven't yet is because i can't prove through process of elimination whether is engine or mechanical. just can't find anything on it that looks bad or doesn't work. i only use it on my yard and mower has only 130 hrs on it after 5 years. another reason i haven't swapped engines yet is i can't stand not knowing why this one won't perform.

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Must be some pretty thin grass you have if they are mowing it at those speeds with a finish mower.
The thick grass around here you would need to mow real slow to cut 12" grass with a finish mower of any kind and it would still be a crappy cut. Especially with 24HP it wouldn't happen at much over a crawl.
That's getting into brush mower mowing depth.

Ran a Turf Tiger II if I remember correctly that belonged to a customer a few months ago. Had the 27 EFI Kohler engine, and I don't remember deck size. Either 54 or 60 I just don't remember. Wouldn't handle 6 inch grass cutting 2.5 inches high, and had to creep to prevent killing the engine. Probably couldn't mow more than about 1 mph.

did you solve his issue ilengine? if so would you let me know. may be something i haven't tried. as for the 12 inch grass that was a guess. because of my job and the rain patterns around here i generally go a few weeks between grass cutting unless we are having a drought:laughing: i usually cut at 3.25 deck height and grass may only be 8" but regardless same issue. mower just won't do it without 2/3 passes unless like you said 1mph or less

Tony2 The reason i was repairing this mower was because of intermittent start that came down to a faulty pto switch. In the case of this customers Scag just not enough HP to pull the deck and the hydros. Just too heavy and robbed a lot of power. Engine was running fine.

I suspect it isn't an engine problem, unless you are dropping a cylinder under load which is possible. Not enough fuel to one cylinder under heavy load, or could possibly be loosing spark under full load. Or maybe nothing is wrong at all and it has the same issues of just not enough power to pull itself and keep up with the load of heavy grass.

thanks for the input ilengine. i have always suspected that might be the case

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.

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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?