briggs and stratton motor for inboard power

[kempracing]

I am building my first wood boat , a 14ft from blue prints i bought from clark craft , has any one ever used a 20hp v twin briggs motor for a power plant, any thoughts on this would be very helpful

[Cuyahoga Chuck]

Give us some specifics. Name the design. Is it intended for an inboard? There is more to this idea than jusk plunking the motor on the bottom.
For instance any inboard in a 14 foot skiff is going to take up some of the limited space in the boat.
Would there be enough room around it to walk from front to back by without burning yourself or tipping th boat over?
How much does this motor weigh?
Do you have any idea of what it takes to run a prop shaft out the bottom of the boat and not have a perpetual leak?
Are you aware that having a prop hanging from the bottom makes it more susceptible to damage if you get caught in shallow water?
If this is Clark Craft's 14 foot hydroplane I'll delete this. Hydros and their motors are beyond my abilites.

[Breakaway]

You can make it work. The think is --its air-cooled, right?-- its gonna be loud. So the real question isn't whether you CAN use it; the question is do you want to?

In his book, Pete Culler on Wooden Boats, Culler devotes a whole chapter to methods for propelling boats with engines and fittings from the hardware store. The book is worth the price for that chapter alone.

Kevin

[TerryLL]

Donald Branscom did something similar.

http://forum.woodenboat.com/showthre...oat&highlight=

[James McMullen]

Noi-oi-oisy! You're going to hate every second you're trapped onboard with that high-pitched whine. So will everyone else within earshot. . .and with that motor that's going to include an awful lot of people.

There's an awfully good set of reasons why you don't hear of people doing this sort of thing regularly. A modern water cooled four-stroke outboard is infinitely friendlier and more useful for a 14' skiff.

[pcford]

Donald Branscom did something similar.

http://forum.woodenboat.com/showthre...oat&highlight=

But never reported if the boat work ok.

[pcford]

Noi-oi-oisy! You're going to hate every second you're trapped onboard with that high-pitched whine. So will everyone else within earshot. . .and with that motor that's going to include an awful lot of people.

There's an awfully good set of reasons why you don't hear of people doing this sort of thing regularly. A modern water cooled four-stroke outboard is infinitely friendlier and more useful for a 14' skiff.

Maybe...but the Poulsbo boats were pretty darn successful.

[pipefitter]

They do have 'quieter' mufflers available for the Tecumseh and B&S motors these days.

[James McMullen]

Pat, you know damn well that Poulsbo boats didn't have lightweight, aluminum high-rpm Briggs & Stratton engines in 'em. A 5 horse Wisconsin Robin sounds nothing like that devil screech. You might as well have a leafblower or a chainsaw running onboard.

[TerryLL]

But never reported if the boat work ok.

Yup. I never did see in any of his posts that the boat hit the water and the engine system was tested.

Clark Craft offers a half dozen different 14' designs, all with transoms that could easily take an outboard. I don't quite understand why one would opt for a lawnmower engine inboard.

[pcford]

Pat, you know damn well that Poulsbo boats didn't have lightweight, aluminum high-rpm Briggs & Stratton engines in 'em. A 5 horse Wisconsin Robin sounds nothing like that devil screech. You might as well have a leafblower or a chainsaw running onboard.

Wellsir...I am afraid that you are known to be internal combustion averse...and my very limited experience with small Honda engines...in the form of a small generator...and a five horse Honda outboard...showed them to be amazingly quiet. But I would bow to any evidence you have comparing the Wisconsins and Hondas.

[Breakaway]

I'm a powerboat guy. I run a 250 outboard. Its way quieter-WAY, I say-than the 20-hp Kohler in my lawn tractor.

Kevin

[Bobcat]

A weedeater outboard i e a small air cooled two stroke motor: I would drive nails in my head rather than listen to this

http://www.youtube.com/watch?v=GidrYxImkoU

[Mad Scientist]

...In his book, Pete Culler on Wooden Boats, Culler devotes a whole chapter to methods for propelling boats with engines and fittings from the hardware store. The book is worth the price for that chapter alone.

Kevin

I, too, was captivated by Capt. Pete's description of those boats. I did a little research, and also found some interesting info in this thread: http://forum.woodenboat.com/showthre...vity-Feed-Tank

Check CG regs for small boats - your intended motor might need some mods. Briggs & Stratton should know, but I'm not sure if your intended engine was designed for marine use.

Tom

[wizbang 13]

One can quiet them down with a wet exhaust. the mechanipickle noise remains. air intake is noisy too.
My friends have a mini paulsbo type with a one lung briggs. The dry exhaust has an extension that , I swear, makes it even louder.
talk about a lo jac, the family always knows where it is, 5 miles in any direction.

[Philip Maynard]

The Chesapeake Crabbing skiffs race with Onan 20HP and short upturned straight exhaust, very loud, what you would expect with a race boat. You can find video on the internet.

My 4.5 HP Robin Subaru is quiet below 4.5 knots, above that it gets loud and adds lot of wake and heat but at lower speeds its very reasonable. I'm using the original muffler but relocated with some added piping.

There is a large range of opinion on the noise level. My own experience is at reasonable cruise power settings for a 16 sailboat with 4.5 HP, the noise is not a problem but most people only seem to look at the full power noise level, which IS loud and which I have yet to use other than testing it. If I actually needed full power in normal usage then it would be another story but in real world use, this setup works just fine for me.

This video shows various speeds from idle to full power.

http://youtu.be/D-YgBuYQuIg

[dredbob]

One can quiet them down with a wet exhaust.

Yes. In Annapolis a few years back at some kind of maritime festival there was a fellow who had built a very nice inboard skiff of about 17-20 feet. The power was one of the Industrial/Commercial aircooled engines (I don't remember whether it was a Honda, BS, or what). He had engineered a nice belt drive reduction system, had a small FNR transmission, and a water cooled exhaust. The thing was very quiet, certainly no louder than a small outboard would have been. I was pretty impressed with the setup.

But, the thing is, is that duplicating the system would end up costing as least as much as one of the small four stroke outboards, so I don't see any real advantage to doing it unless you really just want to play with something like that.

Bob

[Cuyahoga Chuck]

They do have 'quieter' mufflers available for the Tecumseh and B&S motors these days.

Much of the noise generated by air-cooled motors comes right thru' the finning. Back in the motorcycle two-stroke days most manufacturers of high powered dirt bike added special rubber wedges to keep the fins from oscillating.

[PeterSibley]

Noi-oi-oisy! You're going to hate every second you're trapped onboard with that high-pitched whine. So will everyone else within earshot. . .and with that motor that's going to include an awful lot of people.

There's an awfully good set of reasons why you don't hear of people doing this sort of thing regularly. A modern water cooled four-stroke outboard is infinitely friendlier and more useful for a 14' skiff.

One advantage of a big motor is that you don't have to run it at 3600 rpm and screaming. At 2000 rpm she will move you along nicely, if not planing but the noise level will be a LOT lower .

[Bob Adams]

Maybe he just wants something unique. Here's an old video of an 8 horse Briggs, if I were doing it I'd be inclined to add a small sea water pump and a waterlift muffler like you would use for a genny.

[kempracing]

Wow , i never thought there would be this many post on my crazy thought about a briggs and stratton motor in a boat , The boat I am building is a clark caft sport runabout 13 , design #cn52 , I plan on changing the design a little , I know its a outboard but I want something differnt , I want somthing that is two seats with the seating to the rear of the boat like from the 30s and 40s , the motor I plan on using came from a race car , the cars are called sling shots , you can look them up on the internet , these motors are pretty quiet in race form and with some exhaust work should be very quiet , and they are electric start , as far as hooking up to a prop shaft this will not be a big deal as i have full access to a machine shop that I can make any adapters needed , I have looked for all the parts needed to make this all happen and most all of it can be found , I know this idea sounds pretty crazy to most boat builders but you have to understand that i already have the motor ( $2500 ) , I have 25 years as a welder fabricator and a full machine shop to work in , as I get to the differnt stages i will post pics so everyone can see , THANK YOU ALL FOR YOUR INPUT , JIM KEMP

[Ron Williamson]

If you'd said all that up front,we'd be asking you for advice.
R

[wizbang 13]

yea, not talking about putt putts.
Got some pics of your build? That is the drug that keeps this place going.

[kempracing]

As soon as I get far enough along I will post lots of pictures , as of now I am just starting to get all the wood so the boat can be put together , I think it will be a fun project with alot of late nights in the shop , like I said this is my first boat build but the blue prints look very easy and are easy to understand , I will keep you all posted

[Cuyahoga Chuck]

As soon as I get far enough along I will post lots of pictures , as of now I am just starting to get all the wood so the boat can be put together , I think it will be a fun project with alot of late nights in the shop , like I said this is my first boat build but the blue prints look very easy and are easy to understand , I will keep you all posted

Don't go away too soon. There are some engineering needs that need to be addressed.

1. a boat prop works in a limited band of RPMs. Too many and the prop cavitates and you lose bite on the water.That RPM is likely to be much different than the operational RPM of your sling shot mill. So you may need a suitable Gear reduction box. Most of the outboards I'm familiar with seem to have a built in gear reduction in excess of 2:1.
2. Then , for safety and ease of manuerver you should have a Forward/Neutral/Reverse capability.
3. I'm adding this because my google for "Sling shot cars" didn't get me any specifics about the B&S motor. Just about all front motored runabouts of the past had watercooled motors. That is because the heat coming off the motor has to be tempered so as not to roast the passengers. An aircooled motor pouring heat to the rear could make passengers very uncomfortable if it's warm out.

[Cogeniac]

I think the biggest issue here, aside from noise and exhaust management (which could be worked out), is the space and the heat. An air cooled lawnmower engine needs some airflow around it to cool. That air, and the hot parts of the engine, will be right where folks want to sit.. hard to see how to avoid that in such a small boat.

[donald branscom]

I have run my Honda engine in my boat at least once every few months while I finish my rigging and sails.
The engine is very quiet. I could change over to rubber belt drive. I do not like the tooth rubber belts because they have to be under a lot of tension to prevent slippage.

I know it has been some time since you got a report. Sorry.

The reason I have the inboard engine is for safety at sea.

Almost all outboard engines have a 2 :1 gear reduction Close to that.

My Honda EX160 has 2:1 gear reduction with a wet centrifugal clutch.
As soon as the engine starts to go above idle the prop starts to turn.
I have a regular outboard prop.

[timo4352]

There is a little bit of info in Reuel Paker's Sharpie Book on ar cooled inboard motor installation.

[coelacanth2]

Mentioned also in Buehler's Backyard Boat Building. IIRC our hosts did an article on Black Spirit and mentioned that she was given a Briggsey just to be legal for one race.

[v10builder1]

I like Donald Branscome's design, especially with a suitably wide toothed belt and a guard. I too was skeptical, but they are used now as drive belts on big motorcycles.

Only thing I see missing, and it might not be too big a deal at the engine sizes we are discussing, but the shaft assembly could/should include a thrust bearing to take the forward force on the shaft produced by the prop. The pillow blocks used on the shaft are OK, but the side force on them is not normal, but not normal enough to cause problems down the road, I don't know. I don't have access to the other books suggested in the thread, msybe the issue was covered there. The thrust bearing in my boat's Velvet Drive is a piece of work running in oil, but that is 210 HP turning a 24" prop. As many have said before, just my two cents worth.

Boat on.

Joe

[donald branscom]

I like Donald Branscome's design, especially with a suitably wide toothed belt and a guard. I too was skeptical, but they are used now as drive belts on big motorcycles.

Only thing I see missing, and it might not be too big a deal at the engine sizes we are discussing, but the shaft assembly could/should include a thrust bearing to take the forward force on the shaft produced by the prop. The pillow blocks used on the shaft are OK, but the side force on them is not normal, but not normal enough to cause problems down the road, I don't know. I don't have access to the other books suggested in the thread, msybe the issue was covered there. The thrust bearing in my boat's Velvet Drive is a piece of work running in oil, but that is 210 HP turning a 24" prop. As many have said before, just my two cents worth.

Boat on.

Joe

I have added thrust bearings to my drive set up.

[Philip Maynard]

Also in my video I had the seat off to show the engine but normally I run with the seat on, you can sit on it.

[mcdenny]

Jim, a high speed runabout (specs say up to 50mph with 20 to 40 hp outboard) is very sensitive to weight distribution. Moving the engine from the transom to the middle or even more forward will have a big effect on how the boat handles. You will want to move the passenger weight aft so the center of gravity of your modified boat is near the same place as the boat as designed.

Often small boats like this benefit from hanging the motor on a bracket maybe 6" behind the transom.

Denny Wolfe

[kempracing]

Denny , Ya the plan is to move the passenger compartment to the back of the boat , the motor only weighs about 80 lbs so I am going to have figure the balance out when I get to that point , there has been alot of great post on here about trying to make this happen , one about how do I get the heat from the motor from cooking the passengers , that I will take care of by running duct work to the air intake at the fan side and matching duct on the other side sending it out through vents out the back of the boat , The exhaust will run through the out going duct work which will help keep it cool ( somewhat ) and help protect the wood of the frame , I am now also looking into a trans so it will have f/n/r , there are many ways of doing this by useing a boat type trans or I am also looking at race car style trans , not sure on this yet but thats going to be the most fun about this project is just figuring out all of these things , not to mention that i still have to get the boat togther , with the help from people on this form its makes me think about a lot of these issues so keep the post coming and call me a idot if you think I am out of my mind for trying this as thats ok some of the best things we have in this world were dreamed up by some crazy fool in a barn , I will have pics up as soon as i can

[mvtofino]

I don't want to discourage your cutting edge thinking, but I would like to add a couple of comments for your consideration:

1. Corrosion: I did not read in any of the thread's posts where you intend to operate this vessel, more particularly, in a fresh or salt water environment. If the latter, then you will want to pay close attention to the many corrosion issues you will immediately face. Very few non-marine designed components are suitable for use in a salt water application, even when the user intends to trailer the vessel and wash it out with fresh water after each use. It is amazing how quickly a salt environment will destroy metals, consume dollars, frustrate humans and waste hours!

2. Weight: While you mention the B&S engine weighs only 80 pounds, by the time you fabricate a wet exhaust system to marine specifications, as well as find an appropriately sized reverse gear (if one is currently being manufactured, which I doubt...), you will have easily doubled or more likely tripled the engine's weight or even more. It should be remembered that this is a 14 footer with dimensional limitations based on reasonableness or else it risks becoming a throwback to the late 1800's/early 1900's where steam propulsion was the order of the day, and much of the people space was devoted to inefficient and dangerous mechanicals;

3. Safety: I can't quote you the statistics, but speaking as a former Canadian Coast Guard Auxilliarst (Unit Training Officer & SAR Tech) and Power Squadron Instructor, there always seemed to be a link between boating accidents and landlubber binder-twine solutions to saving a buck while in pursuit of a good time on the water. If your car breaks down, chances are you will call a taxi or take a bus to get home safely. If your boat breaks down, it ain't that simple. Worse yet - fire is the maritime horror to avoid at all costs, which is one of the reasons that pretty well all air-cooled engines in marine use are referred to as "outboards" and are wisely hung off the transom of a vessel instead of being mounted within the people space of a small boat where it is a potential and very real fire risk;

4. Personal experience: My father-in-law passed on a no-name 9 horse-power outboard motor that he purchased in the 1970's from one of the large department stores, most likely Sears. It was an interesting configuration powered by a single cylinder Tecumseh lawnmower or garden tractor engine connected to the propeller by a direct-drive shaft (no neutral or reverse capability) and protected by a shear pin in the event of an underwater collision with the bottom or a dead-head or whatever. The whole drive line could rotate 360 degrees and thus provide a form of reversing, however it was not the preferred way to accomplish the task in my opinion. It was outrageously loud, not just the exhaust but the mechanicals as well, and after running once in the marine environment, the non-ferrous alloys corroded with a flaky, chalky surface material and the ferrous metal rusted and seized. Put simply, the machine was not designed to be used in a marine environment - period. This was as bad an idea as would be modifying my Evinrude to cut the grass! On second thought, Cadillac's outstanding Northstar 32 automobile engine was built by a Mercury Marine/Yamaha consortium, so what do I know...

Do focus on the safety issues especially in a salt water environment.

Good luck with your project!

JT