# Briggs vs Kohler and the state of the market for modifications

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#### karmarepair

##### Well-Known Member
HBA Supporter
Bottom Line Up Front: The Mud Motor market is 10 times the size of the Tractor Racing/Pulling market and will come to drive the modification market, and Briggs OWNS this market.

Surface drives for marine propulsion have been around since the Hickman Sea Sled of 1914. http://en.wikipedia.org/wiki/Hickman_sea_sled The prop is only immersed up to it's hub; half of it is out of the water, and a special supercavitating/superventilating prop is used. Later incarnations were developed in Southeast Asia ("Longtail" Long-tail boat - Wikipedia ), and in the San Francisco Bay Area as the Arnesson Surface Drive (http://www.powerandmotoryacht.com/boats/arneson-drive#:~:text=The%20Arneson%20Surface%20Drive%20%28ASD%29%20is%20actually%20a,he%20invented%20a%20device%20that%20automatically%20cleaned%20pools) starting in the 1970s. These things have been adopted and embraced and developed by the hunting/fishing crowd in the South and Midwest to access water too shallow to drown in, but not too clogged with weed (airboats are still superior for that).

Brands include Beavertail, Mud-Skipper, Mud Walker, MudBuddy, Swamp Runner, Copperhead, Gator-Tail. mud motors - Bing And it's Briggs, Briggs, Briggs. They have embraced this market, and the top of the heap is their 993cc big block EFI engine, rated at 40 HP @ 3600 RPM, with factory authorized governed speed up to 4750 RPM, WITH a 3 year warranty. Vertical: http://www.vanguardpower.com/na/en_us/product-catalog/engines/big-block-vtwin-vertical-shaft/vanguard-400-gross-hp-efi--marine.html and Horizontal http://www.vanguardpower.com/na/en_us/product-catalog/engines/big-block-vtwin-horizontal-shaft/vanguard-400-gross-hp-efi--marine.html

I have it directly from one of the modification shops that they are concentrating their development fire on THIS engine. People run the snot out of them till the warranty runs out, then mod the hell out of them in the first rebuild. And this service is much more like aviation usage than tractor pulling, or tractor dirt track racing. Picture an aluminum jon boat with 3 guys, and a load of decoys running flat-out for 10-15 miles to THE SPOT from the nearest launch ramp. Expect big throttle bodies to use with the EFI, better rods, better valve trains, etc.

This is not to say that development on the Kohler CH750 (their mid-sized engine, they also have a Big Block, see TiPi's build thread for an overview of the various classes of engines from the major manufacturers.) is dead. It's still the favorite of the tractor pullers, and there are 2 different brand new CNC hemi heads for this engine, for example (Midwest Super Cubs and Zach Kerber Engineering).

There has been a lot of useful discussion on other recent threads under this forum heading, including on some of the deficiencies of the Kohler. I've also asked the Admins for separate discussion area for Small Industrial V-Twins. And this video by Lonestar Hovercraft compares 3 different brands of roughly 25 HP engines, with a slight win for Kohler http://www.bing.com/videos/search?q=lone+star+hovercraft+briggs+kohler+predator&&view=detail&mid=DFF894FCC0F6EF74E8D8DFF894FCC0F6EF74E8D8&&FORM=VRDGAR&ru=/videos/search?q=lone+star+hovercraft+briggs+kohler+predator&FORM=HDRSC3

#### Vigilant1

##### Well-Known Member
If it's "Kohler vs Briggs" (per the thread title), I'm not seeing much love for the Kohler (per your OP, and TiPi's brief comparison of engines in the sub-900cc range.) The Kohler's are heavy and have a cast crankshaft, a Vanguard ("Briggs Lexus") engine lets you have a forged crank and forged rods, plus some other extras. There's a considerable jump in weight and base engine cost if we go above 900cc, though this may be the price to pay if we want/need more than 30-35 HP.

So, what is the mission/target HP/weight/cost you are after? Want to run it with a PSRU, or direct drive?

At some point as we go up, the weight/cost/complexity of an industrial engine with a PSRU starts to make the 1/2VW and simple 4-cyl VWs look pretty good. Scott Casler will sell anyone a 37HP 1/2VW 1037cc engine, already built, with a prop hub, hand-start, for $3850, and it weighs 85 lbs. Add$650 and some pounds for a starter and alternator.

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#### cluttonfred

##### Well-Known Member
HBA Supporter
I think this topic really ends up dividing folks into two groups--grease monkey vs. instructables. The grease monkey types have grown up taking apart and putting together engines large and small and are comfortable, for example, doing major work on an old car engine. The instructables types are reasonably handy and happy to take on the challenge of something new, but don't have any significant engine knowledge or experience.

For small industrial engines to really take off (pun intended) in light aircraft, we need an instructables solution. A straightforward DIY manual that tells a willing novice how to take a common industrial engine, remove what's not needed and add whatever is needed to turn it into a simple, affordable light aircraft engine. Someone could sell the manual or provide it for free and instead sell parts (prop hub adapter, cooling shroud, redrive if needed, etc.) to make a buck.

No, it won't power an RV-X and no it won't make it to a 2,000 hour TBO. But it will power a simple affordable light aircraft along the lines of a MiniMax (if a tractor) or Hovey Beta Bird (if a pusher) but with the wing area and structural strength for a hefty pilot. This would not be a Part 103 design but it would be a European microlight or U.S. LSA. Modern materials and design can build a modern equivalent of an Aeronca C-2 that could do the job.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
If I were building a Mud Boat this does look like the best engine option. I just checked the parts manual for these and the vertical shavt version does have the external style oil pump so those of us that want to convert to inverted - could - use these.

The Hp is obviously there but I'd like to see a good weight comparison to the small block 810. I suspect that there could be a market for both the big block conversion with EFI and for a carb version of the 810 for planes that need light weight more than power.

As far as Kohler vs Briggs: When I started down this path years ago I was leaning to the Kohler. Better specs being my thought back them. Since then I've decided that Briggs is a better compromise for weight/power/durability/ weight.

The fact that the B+S site specifically lists Mud Boats among the options with mowers and chippers probably means that there will be a good supply of engines for 'recreational' use.

#### pictsidhe

##### Well-Known Member
I think this topic really ends up dividing folks into two groups--grease monkey vs. instructables. The grease monkey types have grown up taking apart and putting together engines large and small and are comfortable, for example, doing major work on an old car engine. The instructables types are reasonably handy and happy to take on the challenge of something new, but don't have any significant engine knowledge or experience.

For small industrial engines to really take off (pun intended) in light aircraft, we need an instructables solution. A straightforward DIY manual that tells a willing novice how to take a common industrial engine, remove what's not needed and add whatever is needed to turn it into a simple, affordable light aircraft engine. Someone could sell the manual or provide it for free and instead sell parts (prop hub adapter, cooling shroud, redrive if needed, etc.) to make a buck.

No, it won't power an RV-X and no it won't make it to a 2,000 hour TBO. But it will power a simple affordable light aircraft along the lines of a MiniMax (if a tractor) or Hovey Beta Bird (if a pusher) but with the wing area and structural strength for a hefty pilot. This would not be a Part 103 design but it would be a European microlight or U.S. LSA. Modern materials and design can build a modern equivalent of an Aeronca C-2 that could do the job.
This is what I am considering doing. Making a kit of conversion parts. These engines are quite possibly the simplest engines to work on. The only special tool needed past sockets, spanners are a flywheel puller and feeler gauges. Those are not hard to buy or improvise.

An 810 looks like it can be converted into a ~25hp direct drive 277 replacement. So 103 industrials are possible. At higher weight and cost, a slightly more powerful 30hp redriven version could swing large props. With water injection, perhaps 35-40hp. Once we start on the litre size, we have a base engine price over 2k instead of around $1000, and the cost increases. To try and stave off briggs' lawyers, such kits should be sold for.'airboat' use. There is a lot of nonsense being repeated about high power levels being easily attainable with a few bolt on parts. Power can only be modestly increased without major cooling upgrades. On engines like these, that is not simple. The power claims are also based on very short dyno pulls of dubious accuracy. Many of these hopped up cart engines claim higher BMEP than megabuck NASCAR engines... #### cluttonfred ##### Well-Known Member HBA Supporter I would suggest starting with a larger engine that produces a verified 30 hp or more in stock configuration. You really need to put yourself into the mind of a novice. Even though the big Kohlers run about$3,000 for 37-40 hp they would still be a bargain if you could spend less than $1,000 on an Ace redrive and an exhaust system and be done. #### TLAR ##### Member You won’t have the instructable without the grease monkey lol And usually the grease monkey ain’t gonna tell ya how to do it Funny ain’t it #### blane.c ##### Well-Known Member HBA Supporter I think everything to make them as light as possible and as simple is best route for most. Simple direct drive wood prop diameter and pitch to make 3400rpm to 3500rpm static and cruise around 3200rpm to 3300rpm more or less. #### Hot Wings ##### Grumpy Cynic HBA Supporter Log Member big Kohlers run about$3,000 for 37-40 hp they would still be a bargain if you could spend less than $1,000 on an Ace redriv That puts you within a couple hundred$'s of a typical 1/2 VW ready to bolt on.

Like Pictsidhe I'm thinking parts kit along with detailed instructions. There may be some core charges involved if the case or crank end up needing to be modified. For someone that routienly changes their own auto oil I'd expect them to be able to convert an 810 in a weekend with a kit. Engine mount and cowling would still have to be air-frame specific.

#### Vigilant1

##### Well-Known Member
Like Pictsidhe I'm thinking parts kit along with detailed instructions. There may be some core charges involved if the case or crank end up needing to be modified. For someone that routienly changes their own auto oil I'd expect them to be able to convert an 810 in a weekend with a kit. Engine mount and cowling would still have to be air-frame specific.
Having the customer do the bolt-on modifications avoids a lot of logistical hassle of warehousing engines. I would think there's room for at least 3 flavors between heads-up, heads-down, and PTO vs flywheel drive (different costs, weights, features). Modified heads/ports and maybe even a custom cam grind could be esp important for anyone wanting to turn a relatively long prop at low RPM.
GPAS did well with an instruction book, a DVD, and selling the parts. In today's environment, the book and DVD would best be sold at cost (they'll be on The Web in less than a week) and any money made will be through the sale of parts and maybe a few fully assembled engines.

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#### proppastie

##### Well-Known Member
Log Member
25hp direct drive 277 replacement.
not sure true part 103 can afford the extra weight......most existing kit/popular 103 are close the 254 limit?......even say the Sparrowhawk UL glider at 147 lb CF and all....add 90 lb engine and you are almost 254. How much is the prop, exhaust and mount going to weigh?...I use that as an example of a high tech CF aircraft even though it would not qualify part 103 because of speed and stall.....I think we would need some new airframes for to use these engines in a part 103.....The Belite would be too heavy I think.

#### Vigilant1

##### Well-Known Member
The MiniSport version of the B&S 810cc weighs 72 lbs, and they haven't gone to extreme measures to get it as light as it could be. Lighten the flywheel more, eliminate the starter, etc. Weight for the engine mount prop, etc won't be appreciably different from a 2 stroke.
No doubt that Pt 103 would be a challenge, but using one of these engines might not require entirely new airframes.

#### proppastie

##### Well-Known Member
Log Member
In today's environment, the book and DVD would best be sold at cost (they'll be on The Web in less than a week) and any money made will be through the sale of parts and maybe a few fully assembled engines.
did I miss something.....are you going to try to make a small fortune in aviation?

#### Vigilant1

##### Well-Known Member
did I miss something.....are you going to try to make a small fortune in aviation?
Oh, no. Life's not long enough to make every mistake

#### proppastie

##### Well-Known Member
Log Member
Oh, no. Life's not long enough to make every mistake
hope you will share the link when it comes up.

#### Vigilant1

##### Well-Known Member
In today's environment, the book and DVD would best be sold at cost (they'll be on The Web in less than a week)
did I miss something.....are you going to try to make a small fortune in aviation?
hope you will share the link when it comes up.
Sorry, I meant that any book or DVD made by anyone is likely to be pirated and avaibale for free on the interwebs in a matter of days.

#### karmarepair

##### Well-Known Member
HBA Supporter
If it's "Kohler vs Briggs" (per the thread title), I'm not seeing much love for the Kohler (per your OP, and TiPi's brief comparison of engines in the sub-900cc range.) The Kohler's are heavy and have a cast crankshaft, a Vanguard ("Briggs Lexus") engine lets you have a forged crank and forged rods, plus some other extras.
Briggs doesn't have a Horizontal shaft engine in the 750-800cc range. Smaller, bigger, yes. Going from a 750cc Kohler to the big block, either Kohler or Briggs, cost 20 lbs comparing the "book" values of each. The CH750 also CURRENTLY has the broadest range of hopup stuff, should you want to go there. And, although I haven't asked him yet, Engineer Spacek has, and will probably sell me, a flywheel mount spool prop extension that will achieve the "Instructable" level Bolt It On and Go direct drive conversion. He uses the same extension on his 810 Briggs conversion, but has to drill the flywheel, as the Briggs bolt pattern for the puller is 3 bolts vice 4 for the Kohler.

#### Vigilant1

##### Well-Known Member
Are you already committed to the Kohler (e.g. do you own one already?) Lots of B&S/Vanguard 810s are running fine and powering fixed wing aircraft without a peep, so the steps needed to get them running in horizontal shaft mode are known, it wouldn't require blazing any new trails. You can then have forged crank, forged rods, less weight, more cc's, a lower price, and higher reliability. Obviously, it is your choice, and I'm sure there's something good about the Kohler.

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#### pictsidhe

##### Well-Known Member
A direct drive 810 would be close in weight to a 277. There is well over 20lb to be lost from the flywheel and starter alone. Yes, a prop adaptor adds a few lb back. It can use about the same prop. Engine mount should be similar weight, if not shape.

#### WonderousMountain

##### Well-Known Member
Watched a few instructionals.
Zach Kerber has a CNC breather plate. Problem solved.
One of them showed a ductile iron stroker Crank.
another refurbished with new valves & a maxxed out bore.

The market does seem to be getting along.
With a good build up plan and an improved
Crank, I think the Kohler's is in contention.