Air cooled outboards?

[C08]

I am thinking of buying a 5hp Yamaha which is air cooled. Is there anything to think about which is different to a normal outboard, apart from no impellers. My interest in air cooled is that it should be lighter than a water cooler but I wonder about the air out vents and whether that make the outboard engine more liable to water ingress onto the electrics and then cutting out? Any views on these engines.
I once had an old Ailsa Craig air cooled outboard engine made by Tomos which was a great engine but even that had a quirk in the you could not run it out of water as the shaft at the bottom was water lubricated and could be damaged by running it dry.

 

[CLB]

Don't know about the Yamaha but some air cooled outboards still have an impeller. Like you say the bottom half and exhaust is water cooled.

 

[fredrussell]

Air cooled engines are generally noisier than water-cooled. Worth considering if it'll be used for long periods.

 

[VicS]

I am thinking of buying a 5hp Yamaha which is air cooled. Is there anything to think about which is different to a normal outboard, apart from no impellers. My interest in air cooled is that it should be lighter than a water cooler but I wonder about the air out vents and whether that make the outboard engine more liable to water ingress onto the electrics and then cutting out? Any views on these engines.
I once had an old Ailsa Craig air cooled outboard engine made by Tomos which was a great engine but even that had a quirk in the you could not run it out of water as the shaft at the bottom was water lubricated and could be damaged by running it dry.

Air cooled may be noisier

I had ( still have, but relegated to a cobwebbed and rat infested corner of the garage ) a Volvo Penta 5 hp which is air cooled ... Oh how much quieter the Evinrude is!.
The VP has a water cooled exhaust but no impeller, water being driven up a tube from a scoop behind the prop. I believe the Yamaha is similar in this respect

I Doubt you will find much available in the way of spares for the Yamaha. I dont think you will even find it listed on the Yamaha parts site.
It was rebadged as a Mariner and although there are diagrams and parts lists on line for that most parts are obsolete.

I would not buy one but if you think the Ailsa Craig was "a great engine" you will probably think the Yamaha "fantastic" ... at least until you need any parts

 

[anoccasionalyachtsman]

I may be missing something, but I can't see why air cooling would weigh significantly less than water. By the time a large enough area of cooling fins, and probably a fan, have been added a small water pump and jacket can't be very different weight-wise?

 

[CLB]

I may be missing something, but I can't see why air cooling would weigh significantly less than water. By the time a large enough area of cooling fins, and probably a fan, have been added a small water pump and jacket can't be very different weight-wise?

The fan is usually built onto the flywheel. Fins are very light. The extra weigh comes about with the extra heavy metal used on the engine block and head to create all the water passages AFAIK

 

[VicS]

I may be missing something, but I can't see why air cooling would weigh significantly less than water. By the time a large enough area of cooling fins, and probably a fan, have been added a small water pump and jacket can't be very different weight-wise?

there may be not a lot of difference my old VP weighs 19.5kg.
A near equivalent water cooled engine would perhaps have been a 4 hp deluxe Evinrude. That would have weighed 22.7 kg

 

[Tranona]

The main attraction of air cooled is simplicity of construction and in some cases such as the popular Honda 2.3, the ability to use an existing engine in what is (by Honda standards) a very small market. Those with long memories will recall similar approaches dating back to the 1930s with engines like the Atco. Fortunately all eclipsed in the market at the time by the far superior water cooled Seagull.

 

[NormanS]

There's a big advantage in an air cooled outboard if you don't have ready access to a means of flushing with fresh. My boat is either on a swinging mooring, or away cruising, so opportunities for flushing are rare. This leads to the water galleries on the little Mariner getting clogged. Grr!

 

[ex-Gladys]

There's a big advantage in an air cooled outboard if you don't have ready access to a means of flushing with fresh. My boat is either on a swinging mooring, or away cruising, so opportunities for flushing are rare. This leads to the water galleries on the little Mariner getting clogged. Grr!

Although I wouldn't want a noisy air cooled outboard, one of the issues with water cooled, is that they generally don't run hot enough to really combust the oil. Certainly don't use chainsaw or old lawnmower 2 stroke oil in an outboard

 

[DownWest]

I have a 3.5 aircooled Yam. Dates from 1980 and has the exhaust cooling from a bit of tube that faces the prop. Swopped it as a non runner in about '02? and after a clean out of the fuel system, it has started and run ever since. Yes, it is a bit noisier than a 4T or even a 2T of the same power, but it has cost zero since I got it and is the most eliable engine I have used, bar non.

Correction, I bought a fresh plug about 5 yrs ago.

 

[James_Calvert]

...the far superior water cooled Seagull.

Words to relish if not always to agree with!

 

[Tranona]

Words to relish if not always to agree with!

Remember I am talking about 1938 - but still reasonably relevant until the 1970s as owners of horrid things like Johnson Seahorses will tell you!

 

[James_Calvert]

Remember I am talking about 1938 - but still reasonably relevant until the 1970s as owners of horrid things like Johnson Seahorses will tell you!

With apologies to the OP for stealing his thread... My father bought an Evinrude 3 hp twin in 1964. A year or so later I, as a 10 year old, was able to start it. Doubt I could have done that with the equivalent single cylinder Seagull. A few years later we had a Johnson 9.5. Very quiet and my favourite engine. Currently still have an Evinrude 4 hp, direct descendant of the old 3 hp, and still prized by many today.

Just saying...

Obviously you had some issues with OMC Johnsons? We didn't, the 9.5 even survived a number of overnight dunkings when the dinghy to which it was attached turned turtle on its mooring during gales.

 

[Tranona]

Perhaps I should own up to having worked for Seagull. However not blind to their deficiencies, but also rather more aware than most of the properties of competitors at the time in a global rather than individual sense. So, like most products there are good stories and bad but for most of the small hp engines up to the late 70's when the Japanese came in, the story was overwhelmingly bad. That is why the Seagull existed - it was less bad overall than the competitors!

 

[James_Calvert]

Perhaps I should own up to having worked for Seagull. However not blind to their deficiencies, but also rather more aware than most of the properties of competitors at the time in a global rather than individual sense. So, like most products there are good stories and bad but for most of the small hp engines up to the late 70's when the Japanese came in, the story was overwhelmingly bad. That is why the Seagull existed - it was less bad overall than the competitors!

Now I understand (I'd forgotten your Seagull connection).

The Salcombe chandler from whom my father bought the Evinrude Lightwin (3hp) actually allowed him to try out a Seagull 40 something first, but he preferred the convenience of the recoil starter, its lighter weight, its weedless propellor, and the relative quietness and even firing of the aluminium twin cylinder Evinrude. Interesting that the chandlery stocked both. Obviously the Seagull offered something different. Colonel ( Robin ?) Brandon was the guy in charge, maybe you knew him?

 

[Burnham Bob]

My Honda is air cooled and yes it's noisy. But no need to flush it after use and no impellor to replace. However, I grew up with seagulls in the 60s and in recent years loved my 40 plus until it finally died.

 

[Even Chance]

I have an old Yamaha 5BS aircooled outboard from around 1980 era. Its a bit noisy, but it runs well.

 

[JimC]

... That is why the Seagull existed - it was less bad overall than the competitors!

British Anzani were one of the principal competitors as I recall. They used to have full page adverts in the mags for their range of outboards: http://www.britishanzani.co.uk/HISTORY4.htm I think at least some of these were air-cooled.

 

[Dorset Dave]

My Honda is air cooled and yes it's noisy. But no need to flush it after use and no impellor to replace. However, I grew up with seagulls in the 60s and in recent years loved my 40 plus until it finally died.

Thanks for all the great experience above. We're just going to buy a (well) used Marina 5 air cooled, but we've not seen it in the flesh yet, can anyone please confirm, are the air-cools noisy because they do not exhaust under water? If that's the case, could you modify it with a tube to exhaust under water? Thanks.