Very small inboard engine?

[TwoHooter]

Is there such a thing as a very small petrol or maybe diesel (not electric) inboard engine, perhaps 7 HP, which could be fitted to an equally small traditional dinghy, about 10' x 5', for use as a tender? At the moment our tender is a BRIG Falcon 330 RIB with a 20HP outboard but we only use it for going ashore and after 9 years and over 50 different berths and anchorages we've never wanted to run it much above tickover due to speed limits. And neither me nor my wife have any desire to go fast anyway. Our main boat only does 7kts. We are slow fair-weather boaters. I'd much rather have a traditional boat as our tender, and I'm fed up with the complications of modern outboards. I'd be happier with an old fashioned simple little inboard engine. I might even go for a wood tender if I can find a tiny engine. Any ideas? I suspect I'm 50 years out of date here as with most things :-(

 

[B27]

Yes.
A mate of mine has inboard diesels from about 2cc upwards, for radio control models.
There are vintage inboards like Stuart Turner.

But if a petrol outboard has excess 'complications' maybe you want electric?

There are some interesting vintage electric boats come to that...

 

[bedouin]

There are plenty of small engines available on the market - used in all sorts of things like lawn mowers, generators and so on. But would say that is the least of your problems - trying to fit prop shaft etc to an older boat seems like a lot of work to me.

 

[jwilson]

Sounds like you are in the market for a Torqueedo or Remigo electric outboard .... I've had a lift ashore in a dinghy with with a Torqueedo, and was impressed.

 

[LittleSister]

Nice idea, but I suspect a 2hp (and 2 stroke for lightweight?) outboard, rather than inboard, will be the most practical/achievable solution.

In dream world I think a small Wankel rotary engine could be good. V small and lightweight, happiest running at constant-ish revs, and use on a boat would reduce the significance of their weaknesses of somewhat higher fuel consumption and rotor tip wear. (I believe they're manufactured in numbers for use in aerial drones, etc., but whether one could buy one of those retail, I don't know.)

For use on a dinghy, an exposed projecting prop is a serious disadvantage, both in terms of risk of grounding, and if/when one wants to drag it over a pontoon or land. Hence I'd have the fantasy Wankel motor driving a prop/impellor in a tunnel.

 

[ashtead]

Surely a traditional dinghy merits a traditional Seagull outboard. I drifted inshore to the Henley classic boat show and saw a seagull stand with many models. It might be by contacting the Henley boat show which seemed a very traditional place they will have contacts for clinker dinghy and know someone well versed in such craft. Alternative get along to what is lovely old fashioned event with classic cars as well and see what you find. Makes a great day out even if it rains .

 

[trapper guy]

Nice idea, but I suspect a 2hp (and 2 stroke for lightweight?) outboard, rather than inboard, will be the most practical/achievable solution.

In dream world I think a small Wankel rotary engine could be good. V small and lightweight, happiest running at constant-ish revs, and use on a boat would reduce the significance of their weaknesses of somewhat higher fuel consumption and rotor tip wear. (I believe they're manufactured in numbers for use in aerial drones, etc., but whether one could buy one of those retail, I don't know.)

For use on a dinghy, an exposed projecting prop is a serious disadvantage, both in terms of risk of grounding, and if/when one wants to drag it over a pontoon or land. Hence I'd have the fantasy Wankel motor driving a prop/impellor in a tunnel.

wankel engines have a major problem though due to them being heated at only one point on the engine, warping between the main body and the 'cylinder head', from everything ive read they are a major pain, personally one that i would avoid like a plague, unless i was really good friends with an engineer.

 

[Blue Seas]

You could look for an old SABB (8hp iirc) - great little engines, so complicated that the oil filter is a piece of brown paper! Somebody on here might have one occupying a dark corner. Or try Sleeman & Hawken in Teignmouth, they might have an old Sabb kicking around or they do small (less than 5kw) diesels.

Sabb - Sleeman & Hawken - Genuine Spare Parts, Diesel Engines And Generators

 

[dunedin]

Is there such a thing as a very small petrol or maybe diesel (not electric) inboard engine, perhaps 7 HP, which could be fitted to an equally small traditional dinghy, about 10' x 5', for use as a tender? At the moment our tender is a BRIG Falcon 330 RIB with a 20HP outboard but we only use it for going ashore and after 9 years and over 50 different berths and anchorages we've never wanted to run it much above tickover due to speed limits. And neither me nor my wife have any desire to go fast anyway. Our main boat only does 7kts. We are slow fair-weather boaters. I'd much rather have a traditional boat as our tender, and I'm fed up with the complications of modern outboards. I'd be happier with an old fashioned simple little inboard engine. I might even go for a wood tender if I can find a tiny engine. Any ideas? I suspect I'm 50 years out of date here as with most things :-(

What are "the complications of modern outboards" that you refer to?
Feed them new E5 petrol each season and should run fine.
For the cost of fitting an inboard you could probably buy 5 or 6 outboards on eBay and just replace each year
And why rule out electric? For your stated usage a small electric motor and a battery would perhaps bring your ideal inboard engine. Simple, compact, reliable and popular on traditional boats. Or just buy a Torqeedo outboard?

 

[Alicatt]

Yes.
A mate of mine has inboard diesels from about 2cc upwards, for radio control models.
There are vintage inboards like Stuart Turner.

But if a petrol outboard has excess 'complications' maybe you want electric?

There are some interesting vintage electric boats come to that...

We had a Stuart Turner 1.5hp two stroke petrol in our first boat, great little engine powered our 12ft clinker built mahogany over oak tender at 3knots also had a reverse gear, it was the first engine I learned to strip and decoke as a young lad

H. Sykes built 12ft tender 1/2ton of wooden boat Picnic on an island on Loch Morar 1970.

 

[LittleSister]

Sabb engines are incredibly heavy! [Responding to Blues seas' post above.]

If one is looking for old marine engines, a Dolphin petrol engine is compact and lightweight. There used to be a business (in Devon?) that refurbed them and sold spares (and proselytised about their virtues at boat jumbles etc.), but I doubt they still exist.

 

[Blue Seas]

Zackley! So he can hoist a sail too!

 

[jwilson]

You could look for an old SABB (8hp iirc) - great little engines, so complicated that the oil filter is a piece of brown paper! Somebody on here might have one occupying a dark corner. Or try Sleeman & Hawken in Teignmouth, they might have an old Sabb kicking around or they do small (less than 5kw) diesels.

Sabb - Sleeman & Hawken - Genuine Spare Parts, Diesel Engines And Generators

A Sabb would sink a 10 ft dinghy!

 

[wombat88]

Dolphin, Stuart Turner, Vire. I think they are all two stroke petrol, very light and small. 'Very light' is by comparison with a diesel.

However they are all ancient and the Stuart Turner magneto has something of a reputation.

I think the short answer to your question is no there isn't. I'd think about a two stroke tiny outboard. Perfectly adequate for 10 ft.

 

[trapper guy]

Sabb engines are incredibly heavy! [Responding to Blues seas' post above.]

If one is looking for old marine engines, a Dolphin petrol engine is compact and lightweight. There used to be a business (in Devon?) that refurbed them and sold spares (and proselytised about their virtues at boat jumbles etc.), but I doubt they still exist.

my boat was originally fitted with a dolphin, which was later replaced with a beta 14, i bought the boat ith the beta installed, so couldnt give an opinion of a dolphin.

 

[trapper guy]

What are "the complications of modern outboards" that you refer to?
Feed them new E5 petrol each season and should run fine.
For the cost of fitting an inboard you could probably buy 5 or 6 outboards on eBay and just replace each year
And why rule out electric? For your stated usage a small electric motor and a battery would perhaps bring your ideal inboard engine. Simple, compact, reliable and popular on traditional boats. Or just buy a Torqeedo outboard?

imho, you cant keep a recharge for an electric motor in a spare tank, once your batteries are flat, thats it

 

[trapper guy]

Surely a traditional dinghy merits a traditional Seagull outboard. I drifted inshore to the Henley classic boat show and saw a seagull stand with many models. It might be by contacting the Henley boat show which seemed a very traditional place they will have contacts for clinker dinghy and know someone well versed in such craft. Alternative get along to what is lovely old fashioned event with classic cars as well and see what you find. Makes a great day out even if it rains .

have heard many positive opinions about the seagull engines, 'will troll all day on just a cupfull of petrol' being a memorable one

 

[dunedin]

imho, you cant keep a recharge for an electric motor in a spare tank, once your batteries are flat, thats it

Doesn’t look like the OP goes very far in the dinghy, so doesn’t need a lot of power. Many charge via a solar panel, or from the mothership. Or simply take the battery home to recharge.

 

[Blue Seas]

A Sabb would sink a 10 ft dinghy!

It didn't sink my 6' rubber dinghy when I loaded it onboard from the boat to take ashore for a refurb

 

[ylop]

imho, you cant keep a recharge for an electric motor in a spare tank, once your batteries are flat, thats it

Can you not swap a spare battery if that’s a regular concern?