Ok to use a long shaft o/b with my dinghy?

Tranona said:
Do you call 6" difference "small. Why do you think motors are made to suit particular height transoms if it does not make a difference. Of course it is possible to use the wring length, but if you read all the comments above you will see that most people find a long shaft on a dinghy unsatisfactory for a variety of reasons. OK if you are seeking the rare compromise of one motor to do 2 different boats, but for a dedicated dinghy motor best to get the right one for the job.
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The OP is asking whether it is ok to use his long shaft outboard on his dinghy; the answer is YES.
 
A short shift is given at 15" a long shaft at 20" , extra long at 25" and some come in at 30".
I've used many longs (20") on a 15" transom as a temporary measure. There's not really a lot of difference other than a lot more drag. Dingy still handles the same.
If your main boat uses a fairly small outboard then why not also use it on a dingy ?
2010 thread ?.. oops.
 
CAPTAIN FANTASTIC said:
The OP is asking whether it is ok to use his long shaft outboard on his dinghy; the answer is YES.
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Depends on your definition of OK. Nowhere did I say it was not possible just that it is better to use the proper thing. If dinghies were intended for use with long shafts they would have higher transoms and they don't because that defeats the purpose of their design.
 
CAPTAIN FANTASTIC said:
The difference between short and long shaft is relative small. Its perfectly ok to use a long shaft outboard on a inflatable dinghy and you will not be able to tell the difference; i have done it for years.
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That's my experience. I have two long shaft outboards for my Corribee and it's convenient to use them on the dinghy as well. In a blind test the user wouldn't know they were using a long shaft.

I do wonder about that extra bit of leverage on the transom though. Not a problem on a modern inflatable but on a 50yo plywood Mirror I'd be inclined to be careful with the revs and/or put some plywood sheets in the OB clamp to spread the load. (Might be overkill.)

Clearly nobody is ever going to specifically buy a long shaft for a dinghy - there's a hefty premium for those extra inches plus they're less common.
 
This doubles up quite happily on the back of my Folkboat, having had the shaft extended to fit onto Honda's own extension.
Exhaust backpressure isn't an issue, as it's a well engineered item.

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jamie N said:
This doubles up quite happily on the back of my Folkboat, having had the shaft extended to fit onto Honda's own extension.
Exhaust backpressure isn't an issue, as it's a well engineered item.

View attachment 138151View attachment 138152
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Good point, clearly back pressure isn't an issue with some/many engines since the Honda and Tohatsu's long shaft versions are just the short shaft with an insert of extra leg bolted in with no other mods. Plus waves.

Bolt on long shafts. ? What a time to be alive. :D
 
On the Honda the exhaust exits at above water level as the engine's air-cooled, so it is an advantage that isn't easily replicated, and does make it noisier than most others, but having the extension so easily made was the benefit of wistful thinking with a glass of decent wine.
To the original thread issue though, having 6" greater depth brings a pressure difference similar to a variation in atmospheric pressure, as in a High or Low or in an slightly elevated lake I'd have thought.
A quick calculation puts it as a similar difference to that of 60' elevation?
 
jamie N said:
On the Honda the exhaust exits at above water level as the engine's air-cooled, so it is an advantage that isn't easily replicated, and does make it noisier than most others, but having the extension so easily made was the benefit of wistful thinking with a glass of decent wine.
To the original thread issue though, having 6" greater depth brings a pressure difference similar to a variation in atmospheric pressure, as in a High or Low or in an slightly elevated lake I'd have thought.
A quick calculation puts it as a similar difference to that of 60' elevation?
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I'd forgotten the Honda was air cooled. Tremendous advantage IMHO.
 
jamie N said:
On the Honda the exhaust exits at above water level as the engine's air-cooled, so it is an advantage that isn't easily replicated, and does make it noisier than most others, but having the extension so easily made was the benefit of wistful thinking with a glass of decent wine.
To the original thread issue though, having 6" greater depth brings a pressure difference similar to a variation in atmospheric pressure, as in a High or Low or in an slightly elevated lake I'd have thought.
A quick calculation puts it as a similar difference to that of 60' elevation?
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27" of water height equals 1psi , so 6" aint going to have much of an effect on the exhaust.
 
I've used various long shaft on what should be short shaft dinghys ..... the main thing to watch for I found was to make sure leg was not tilted back - to be as vertical as possible ... and that open throttle with care .... no opening too quickly ....

As long as that was observed - all was ok.
 
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