Why aren't there more air-cooled outboards?

[Tinkerer]

Water pumps,related corrosion, and overheating etc are a major bugbear in outboards.<br /><br />Volkswagens show that cheap and reliable air-cooled motors have been available since the 1930's, so the technology is well known. Porsche shows that high output air-cooled motors are also possible.<br /><br />I've got a mid-70's air-cooled 5hp Mariner that works fine, so durable air-cooled outboards are practical and have been possible for at least the last 30 years.<br /><br />What's the reason that manufacturers don't make air-cooled outboards and save us all the problems associated with water cooled ones?<br /><br />Would you rather have a reliable air-cooled outboard (as long as it didn't sound like a Volswagen)?

 

[Hooty]

Re: Why aren't there more air-cooled outboards?

And waste all that water?<br />I imagine it has to do with the amount of cooling required to cool today's high horsepower engines. If you'll notice, a lot of the motorcycles are using fluid cooled engines now days too.<br /><br />c/6<br /><br />Hooty

 

[OBJ]

Re: Why aren't there more air-cooled outboards?

G-day tinker...<br /><br />The Briggs&Stratton company over here, noted for their fine lawn grooming appliances have come out with a 5hp outboard. Guess it runs real good. Don't know about the bigger hp's though. Put a hood around it to keep it quiet and then ya' gotta worry about putting a fan on it to move air and put louvers in the hood for air flow. Seems water is a little better media for cooling.

 

[Scotty Van]

Re: Why aren't there more air-cooled outboards?

Briggs and Straaton has introduced a new 5hp air cooled motor. <br /><br />Seems that 5 hp is popular-is that because this is the upper limit for air cooling?<br /><br />I have seen them testing the motors on a lake that I fish in Wisconsin and they run for hours at idle/no wake speed to get some tough hours on them.<br /><br />lawn mowers on the lake <br /><br />They also run an electric motor with a gas generator on board their little 12' Lunds so they can monitor how the electric motor does for a few hours. Kind of a strange sight that one!

 

[Tinkerer]

Re: Why aren't there more air-cooled outboards?

I was thinking about the fan/louvre issue and protection from water entry with louvres, but I'd rather run a fan than an impeller and it's not hard to seal the electrics against water entry. <br /><br />A fan in a shaker (don't know what you call it in US - air scoop on hood for hot car carby) on top of a big outboard would be neat.

 

[Yepblaze]

Re: Why aren't there more air-cooled outboards?

Most of the "air cooled" motors I've worked on had a water pump to cool the exhaust in the midsection.

 

[DJ]

Re: Why aren't there more air-cooled outboards?

The simple answer is noise.<br /><br />What hp. did the "Bug" engines ever get to-70- maybe? They were cantankerous, at best, and noisy. Not to mention they couldn't dream of meeting emissions laws.<br /><br />Can you imagine the noise a 200 HP. aircooled outboard would make?

 

[Scotty Van]

Re: Why aren't there more air-cooled outboards?

I just saw a feature on the Briggs engines on Wisconsin Outdoors on our local PBS and they said there is no plan to increase hp from 5. I think they make an 8 or 10 but maybe that is not practical.<br /><br />the 5hp is a four stroke that exceeds the 2006 emmission requirements already.<br /><br />I think they are priced in the $650 range.

 

[DJ]

Re: Why aren't there more air-cooled outboards?

Riley,<br /><br />I meant automotive emission laws. By those standards, the 2006 "marine" rating is "filthy".

 

[Tinkerer]

Re: Why aren't there more air-cooled outboards?

djohns<br /><br />Mid-sixties stock Porsches were putting out around 100 to 130 hp. I think Porsche produced much later 250hp plus air-cooled, so big motors are technically feasible, not that a marine version is likely to be affordable, at least if Porsche made it.<br /><br />I wasn't thinking of big air cooled motors, more those in the small fishing boat category up to around 13 to 14 feet. Plenty of ride on lawn mower type engines around up to about 20 hp would seem to be suitable, especially those in common 8 to 11 hp range (assuming hp is measured same as on outboards).<br /><br />Why does noise have to be more of a problem with air-cooled than water cooled, if the exhaust takes the same route in both cases?

 

[NathanY]

Re: Why aren't there more air-cooled outboards?

Are aircooled motors as efficient as water cooled motors? I have no experience with aircooled motors.

 

[DJ]

Re: Why aren't there more air-cooled outboards?

Tinkerer,<br /><br />I realize there were more powerful air cooled engines. For that matter, the Wright Cyclone engines on B-29's were 3,000 hp each.<br /><br />The issue is still noise. Air cooled engines do not benefit from the water jackets natural sound deadening abilities. There is more to deadening sound that muffling the exhaust.<br /><br />Also, outboards run at a very high load ratio. That is, they are running as if going uphill all the time. Heat dissapation is paramount. I'm sure it could be done, but it would be expensive and the noise factor is still there.<br /><br />The future emission laws further torpedo the idea. The only way that manufacturers are going to clean up outboards further is to more closely regulate operating temperatures. That means, they are going to have to run them hotter with much more precise temperature control.<br /><br />That regulation of temp.is near impossible on an air cooled engine..

 

[Tinkerer]

Re: Why aren't there more air-cooled outboards?

djohns<br /><br />I didn't know that such powerful air cooled had been made as on the B 29's.<br /><br />I was wondering if the lack of a water jacket or the air cooling fins somehow contributed to the noise, but I didn't think they'd make as much difference as they obviously do as I thought the detonation noise would be contained in the motor regardless. I was assuming that because most small air cooled have lousy mufflers, like the tin boxes on a lot of lawn mowers, that it was just an exhaust problem. <br /><br />Thanks for the clear explanation.

 

[DDIGGER77]

Re: Why aren't there more air-cooled outboards?

IF YOU PUT THE MUFFLER IN THE WATER IT QUITES IT RIGHT DOWN PUT A 8 HR BRIGG IN THE WATER THROUGH AN AUTO MUFFER AND YOU COULDNT HEAR IT 20 FT AWAY

 

[Squeakit]

Re: Why aren't there more air-cooled outboards?

I have 3 small air-cooled motors and they are all noisy but I can live with that. I like the fact that they are so much lighter in weight. I have a 7hp Sears with a Tecumseh lawnmower-type powerhead that only weighs 35lbs and runs all over the place on it's little built-in gas tank. My old 5.5hp Evinrude Fisherman weighs 56lbs and add a 6gallon metal pressure tank and you're talking serious weight in my little 12ft aluminum boat.

 

[SeaMasterZ@aol.com]

Re: Why aren't there more air-cooled outboards?

I had a four and a half horse Gamefisher ... She pushed my 14 foot semi vee along nicely, to the point that I had a little bait and beer concession running with it (did great til the Marine Police said thats illegal, lol, whew, stopped that business!)<br /><br />she wasnt noisy at all ... of course, I usually ran her at half throttle, but that was all she needed, made a decent wake ... I used to carry a two liter bottle of premix with me for a gas tank, after topping off its vast one pint gas tank ... fishing in grassy sound, one of the stone harbor rental boats broke down, so I towed em back to stone harbor, no sweat, they gave me 20 bucks, a cooler of beer and some sandwiches (which launched the business, lol, hey, it was GREAT for almost two months) <br /><br />Im not sure how long it is in miles from north Wildwood to the rental pier in stone harbor, it was about an hour to wander thru the channels and such, I loved it, Hydrophobia didnt mind the strain of the other boat, loaded with drunken fishermen cheering the old girl on, and once away with the cooler .. lol, they gave me the cooler, I dont know why ... I topped the tank back off, and it was about a cup of fuel to fill it back up, a CUP!!!<br />I had her on half throttle cruise, but still, all that wieght, and my own cooler, and Im a big guy too, just amazing ... went deeper into stone harbor, tried to find scotch bonnet bridge, nailed a ton of flounder and had a ball with my ultralight tackle with some two pound snapper blues, then crabbed low water, quite a long day on the water, plus unloading the beer at a buck a bottle, lol, hey, great day<br /><br />if it would have been bud, well, maybe I wouldnt have started that little venture<br /><br />but as USUAL, ive digressed ... air cooled engines are cheap reliable (bulletproof reliable in my limited experience) and inexpensive to run<br /><br />whats to not like?

 

[andrewkafp]

Re: Why aren't there more air-cooled outboards?

Trust an Aussie to come out with that one... <br />Why indeed.

 

[sharkcat]

Re: Why aren't there more air-cooled outboards?

Tinkerer I think its cos there aint more air filled lakes or oceans for that matter.There seem to be a few air filled heads around tho .Outboards are high performance engines they create heat water is a better coolant than air the better the cooling the more power you can create for a given size of engine.Why in this competetive world would a manufacturer put themselves at a disadvantage by offering an inferior product?If the engines were operated in a weed filled enviroment how could they sell spare parts if the cooling system didnt fail LOL

 

[dkondelik]

Re: Why aren't there more air-cooled outboards?

Back in "the day",.... a colleague of mine, powered a boat using the motor out of a Curtis Jenny. Apparently this wasn't all that uncommon as I've been informed that Curtis also powered a few ferries running up the East Coast. They were limited to about a 1 hour trip as the jugs required periodic "oil" that had to be manually dispensed.<br /><br />Anyway, this "ol-boy" said that his Curtis powered toy would run about 60mph in the rivers & bays. Gave the local constabulary, fits. Back then, nothing could catch him.<br /><br />From what I understand, you can see his boat at the Smithsonian as a few years back, the guy donated it and it is now on display.<br /><br />Air cooled? YUP,… but I bet it was loud enough to hurt.