Use Long shaft on dinghy.

D

deerhound

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I have an Evinrude 4HP, and have been offered a suitable dinghy (8ft) which will take this power but the seller says the engine would be better if it was Short shaft, would my engine still operate on such an installation? surely the only difference is the physical length of leg? would drag be the issue or water getting into where it shouldn't,It would only be used as tender and very rarely at that? any help advise please, JBD
 
JB

JB

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Re: Use Long shaft on dinghy.

It will work, Lurcher, but not as well as a short shaft. Watch out for shallow water, though.
 
S

Solittle

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Re: Use Long shaft on dinghy.

I run a 9.9 long shaft on a 12' tinny with no problems.
 
D

deerhound

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Re: Use Long shaft on dinghy.

Thnks JB and SoLittle, seller emailed me this AM and mentioned that with long shaft it will bend the dinghy in the middle, wonder if that would have the effect of having to keep the revs all the way back and hence make little headway or am I inventing problems. JBD many thanks.
 
TOHATSU GURU

TOHATSU GURU

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Re: Use Long shaft on dinghy.

A longshaft will throw water over the stern and into the boat, create extra drag that will slow you down, cause you to ground and most important of all...People will think you are a dork :)
 
D

deerhound

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Re: Use Long shaft on dinghy.

Please excuse my ignorance! I should have explained better when posting, The dinghy I refer to is an inflateable type (blow up Avon Redcrest) thats what I meant by bending the boat in the middle using a long shaft motor! so really is it possible to use a long shaft motor on an inflateable dinghy? thanks guys sorry for wrongly describing situation. JBD
 
Bigjohn1

Bigjohn1

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Re: Use Long shaft on dinghy.

Lurcher, I will offer some first-hand experience with your specific issue....DO NOT WORRY ABOUT IT and go with that long-shaft engine. Some of what people are telling you (while factually correct) applies to larger boats and they may be losing site of the fact that small inflatable tenders are a different animal. You have an 8' tender and will not be breaking any speed records with a 4hp engine. It is quite common in diving applications to intentionally install a long shaft small outboard on inflatables. As you know, even a slight sea condition causes them to really rock and roll and they end up cavitating MUCH easier than larger vessels. A short shaft engine will cavitate much easier so many install the long shaft engines. You are not worried about water spray as that boat aint going to be going that fast. Enjoy the boat and install the long shaft....you will not regret it.
 
D

deerhound

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Re: Use Long shaft on dinghy.

Many thanks BigJohn 1 for reply, I noticed in a boat magazine that main dealers were selling new inflatables with long shafts! their comment was that the long shaft is best suited to the boat and also that the engine will be compatable to most other applications other than a short shaft? have decided to use long on inflatable, thanks for help again, JBD
 
TOHATSU GURU

TOHATSU GURU

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Re: Use Long shaft on dinghy.

A longshaft engine on a shortshaft boat IS a huge mistake. Call your boat manufactuer and ask them why. Also, no dealer, who knows anything, is putting longshaft engines on inflatables that are designed for shortshafts. This is what I do for a living guys. Just because you have seen someone do it does not mean it is a good idea.
 
B

BillP

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Re: Use Long shaft on dinghy.

I don't know if it is such a big deal on a low performance dink type boat...<br />I had a 4omc longshaft on two 8' dinks and a 10' dink...total time approx 4 yrs (2 cruising & 2 dockside) It was too much power so most of the time they ran at 1/2 throttle. Beaching was the only time I could tell any difference and they manually tilt easy so that didn't bother me either. I still have the 10'r but the 4 was replaced with a 3omc short shaft.
 
TOHATSU GURU

TOHATSU GURU

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Re: Use Long shaft on dinghy.

It's not that you can't do it...I have sailboaters who use their longshafts on their dinghy as well as their sailboat. They have to use the long on the sailboat so the dink is the one that gets saddled with the wrong shaft length. My point is that a long on a short transom only degrades the performance. There is just no benefit that derives from it. That doesn't mean that if you use a long on a short transom that the world will come to an end. Other than grounding a lot more often you might not see any difference. But, If you have a horsepower size that would just plane the boat in a short...Going to a long will not get you up on plane. Anyone that has a longshaft engine can end the problem by buying a mini-jacker plate, put it on your short transom and you are non-dork looking again :)
 
D

deerhound

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Re: Use Long shaft on dinghy.

All good information Gentlemen, I wonder if anything can be fitted to transom of inflatable when using long shaft engine? JBD
 
H

haddles

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Re: Use Long shaft on dinghy.

I have a quicksilver 300 airdeck and I need to put a nylon plate under the short shaft 4hp to raise it to stop water coming in the back of the boat. There is no problem at lower speeds but 4hp will plane these lightweight boats with just one person on board and that is when the water pours in. I'd imagine a longshaft motor would be terrible at higher speeds assuming the turbulence around the gearbox lets it get there. I doubt you could raise the motor enough unless you devise some strange transom alterations.
 
b.gagnon

b.gagnon

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Re: Use Long shaft on dinghy.

I had a 12' and it came with a long shaft 6hp that would not get out of it's own way! It could not even get on plane with one person. Then I went to a 8hp short shaft and it did 20mph!!!<br />Go with a short shaft.
 
Bigjohn1

Bigjohn1

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Re: Use Long shaft on dinghy.

Everyone has their own personal experiences I guess. 6hp on a 12-footer is too small; the normal range is in the 15-25hp range for that size boat but maybe your brand is different than most of the others on the market. I owned a 14' Achilles designed for a short shaft and powered it with a 40 long...the wake looked a bit weird at 30mph but it ran fine and sprayed ZERO water in the boat. I then owned a 12' Achilles and intentionally powered it with a 25 long...identical running characteristics and speed - low 30's mph, weird-looking wake but no water in the boat. I'll add, zero cavitation in rough seas loaded with dive gear. The three inflatable boats prior (all designed for and powered by short shafts) all cavitated once the seas got lumpy.
 
D

deerhound

Petty Officer 1st Class
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Re: Use Long shaft on dinghy.

I was wondering about using a 4hp long shaft evinrude on an inflatable dinghy of about 8 feet in length? thanks for information, JBD
 
G

gss036

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Re: Use Long shaft on dinghy.

Have fun and enjoy yourself. Nothing is wrong with the application, especially with a small dingy as you are not going to be going that fast in the first place.
 
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