Our neighbor was running one of these when mulching on a 10515, about the same hp as yours but newer. The engine overheated and ruined the piston and cylinder. The cooling fins were not plugged nor was the exhaust ports. I had parts and was able to resurrect it for him.

Walt conner

I have used the mulch fan that came on my 10201 and 10550 for many years with no problems. I took it off the 10550 because I was using it as my dedicated bagger. I decided to mulch with it last night, forgetting the mulch fan was off. I didn't notice any difference and never thought about it until I read this post. I'd say if it mulches satisfactorily without it, don't put it on. I doubt if use of the mulch fan could be the sole cause of overheating.

It seems to act more like a blower with the fan on. Seems to stir up old grass better maybe making it easier to get in the clippings bag.I haven't been using mine lately on account of on a dry day it blows up too much dirt,etc.,.Sort of works OK for cleaning the sidewalks of debris.

"I doubt if use of the mulch fan could be the sole cause of overheating."

Maybe not but I have worked with/on Lawn Boys for many years and that is the only thing I could find. How much extra load the fan puts on depends on how heavy/good the grass is of course and whether it is August or April. This particular neighbor is very particular with his mower and his yard so neglect or over grown grass is not likely and I had already cautioned him to use LB oil at proper mix.

The use of a mulching plate alone puts considerable additional load on the engine. Add the fan and you have even more. Sure, I know there are going to be a bunch of posts telling how wrong I am but I still contend that the use of a mulching fan with mulching plate loads an "F" or older LB to close to max. in good grass in hot weather and add a few years use to the age of the engine.

Walt Conner

I would agree with you Walt. The fan actually adds four more surfaces of friction to the blade which in term is load on the engine.

An interesting fact that this brings up is 3/4 of the shelled mills I buy are lawnboys with mulch fans attached. Hmmm I wonder if there is some sort of link.

I really like those gator style blades and now I wonder if they are contributing to an early death? Interesting topic.

Neal

Walt; I'm not saying you're wrong, just that I haven't experienced this in seventeen years of operating a 10201 and a 10550. There are engineering reasons behind my opinion. I am getting ready to go play a concert so I don't have time now, but one is that the mulch fan swept area is of a much smaller diameter than the blade swept area. This would place less demand on the engine. I do not believe you will find more throttle opening is required to run 3200 RPM with the mulch fan on. Of course there's the question of the mulch fan causing the grass to be re-cut more, which is it's function, but I have not noticed any apparent added stress on the engine when using it. Not very scientific, but engines give symptoms and clues when they overheat. In short, I can't tell from the engine's behavior if I have a mulch fan on or not.

FWIW.....I put my tachometer on my 10323 to see if the mulching fan changed the motors rpm.I have the governor set at 2900 at full throttle.With the fan on it was a little over 2800 so It knocked the rpm down about 75 rpm, one click worth.

IF the governor is doing its' job, the fan should not knock the rpm down noticeably UNLESS the engine is already at max capacity.

The fact that the fan does not reduce the rpm noticeably does not mean that the load was not increased considerably. Also, taking a reading when not cutting grass doesn't really show much since it is the picked up, recycled grass into the cutting blade that makes the load with the mulching plate in place.

Walt Conner

neither use of a gator blade nor a mulch fan detracts from the lawnboy mulching ability nor harms the engine. i see a inprovement in mulching ability when using the fan esp when mowing thick heavy grass. i use a gator and a mulch fan on allmy lawnboys but i mow commercially so i need max preformance from my machines. the gator and fan is a awesume combo. if you want to talk about a mulching blabe that saps engine power -its the snapper ninja. a f engine in good shape has plenty of power for extreme mowing conditions.

You do not mention using a mulching plate. The addition of a mulching plate at least doubles the load on a lawn mower in my opinion. mulching plate with a fan DO put a heavy load on an "F" engine in thick heavy grass as you describe, commercial mowing or not.

one with 40 years experience.

Walt Conner

Mulching in general obviously requires more power, hence the 6.5 hp mowers of today versus the 3.5 hp when mulching was largely unknown. IIRC, 'F'-engine mowers usually were in the 4 to 4.5 hp range, which I agree would be marginal for mulching, and probably contributes to the overheating seen by Walt. To the original question, I would not put a mulch fan on any LB not originally equipped with it.

as usual walt you are full of bs-i have over 40 yrs of actual mowing experience! not just working on them

Im sure mulching with a lawnboy does not put any more stress on the engine then side discharging through higher thicker grass,just means you walk slower with the mulcher.

I'm posting to an old thread because I've not found one more appropriate.

I resisted installing the mulch fan on my 1999 LB 10323 for more than a decade, even though I mulch more often than bag. I finally decided to install the mulch fan last year as a finishing touch to a re-build of the self-propel transmission and the replacement of the 14 year old drive belt (what a pain!).

I do not detect much, if any, change in the quality of cut. However, an unexpected benefit has surfaced that makes the addition of the mulch fan the second most important improvement to my LB's operation since I replaced that notoriously defective CDI 11 years ago. I could never mow wet grass, or even a minimally moist lawn, without getting massive amounts of caked grass stuck under the mower deck. I'd have to stop periodically to scrap it out. But...since I installed the mulch blade in 2013, there has been no accumulation of grass clippings under the mower deck. I can mow the day after a downpour and find a clean under-deck anytime I check.

So...installing that mulch fan has made my mowing effort much less trouble than in all previous years. I never expected to see this as a result of mulch fan installation.

The 10323 has the 6.5 HP Duraforce engine and originally came with mulch fan installed. Why were you hesitant to use it? My 10201 with 4.5 HP 'V' engine also came with a mulch fan and I used it for many years with no overheating - with the mulch plate installed. I think the Lawn-Boy that overheated had some other problem. Who knows? Maybe Walt's neighbor made a mistake when fueling it and put some straight gas in it. This is the one most frequent cause of 2-cycle engine failure.
BTW, you may wonder how I know my engines never overheated. One way to tell is the idle quality. When you throttle back and it idles normally, there is no excess friction in the engine. With an overheated engine you would also hear the difference in how the engine sounds, plus there would be a 'hot' smell to it. There usually is smoke coming off the engine. Its a violent situation so its not likely that anyone could not notice something major was happening.

I have a 21 inch lawn boy self-propelled mower it works great and has a standard mulching blade. My problem is leaves. I have a tree that constantly drops them. I don't like to mow over them and typically rake them up prior to cutting. I don't currently use a bag on my mower. I was considering the use of the fan blade in combination with the bag to cut the grass and pick up the leaves at the same time. Basically, does the fan blade create more draw into the catch bag? Enough to really suc up those leaves?

The mulching blade also bags, even the 'Atomic' blades with the 'saw teeth' on the back. What mower do you have? I assume its a late model with 4-cycle engine. At first I thought you were talking about the 'mulch fan' which is literally a small diameter air fan that attaches beneath the blade on the old 2-cycle mowers - its not a 'fan blade'. Lawn-Boy/Toro does not make a dedicated bagging blade because the standard mulching blade is adequate for bagging.

Many of us regularly mulch the leaves, even Holly leaves. I'm gradually clearing the back of my property and creating raised areas around the trees or clusters of trees/shrubs that will remain, using mulched lawn debris that I bagged with the standard mulching blade. Now that I'm doing that, I run out of leaves to mulch and no leaf ever has to be bagged and put in the trash or taken anywhere. This mulched debris with mulched grass really composts quickly and turns into humus before your eyes. You don't have to do a thing but place it where you want it about a foot deep and let it happen.