Dink OB - Long Shaft vs Short Shaft

[txh2oskier]

Hi All,I have a Yamaha 8HP 4 stroke with a short (15") shaft. I've been looking for a 15HP 2 stroke and have found one at a good price but it has a long shaft. I don't think I want to go to a long shaft but I don't have a good reason. If it matters, it'll be on a 9' 10" Achilles with a fiberglass hull.

Any suggestions on yes or no?

Thanks.
Brian

[a64pilot]

You don't want a long shaft on a dink, especially if it is a high thrust motor.
I can think of no advantage, but many disadvantages.
It's heavier, takes up more room, more likely to run aground, much poorer performance as drag will be much higher, even burn more fuel due to drag.

[txh2oskier]

Originally Posted by a64pilot

You don't want a long shaft on a dink, especially if it is a high thrust motor.
I can think of no advantage, but many disadvantages.
It's heavier, takes up more room, more likely to run aground, much poorer performance as drag will be much higher, even burn more fuel due to drag.

Thanks, that's along with what I was thinking but wasn't sure I was looking at the entire picture. The friend that found it for me said it was short but 20". I'll have to figure out if it's short or 20", can't be both.

Brian

[a64pilot]

I think outboards are usually 15", 20" and 25".
So to some people a 20" could be considered short? If I were looking for an outboard to power my sailboat, I might call a 20" short, because I'm after a 25".

[Terra Nova]

Originally Posted by a64pilot

You don't want a long shaft on a dink...

This.

[Cheechako]

Some motors are easy to convert to short shaft. Not sure about the Yamaha.

[colemj]

There isn't a rule about long and short shaft - it depends on the specific dinghy.

For your dinghy, the manufacturer recommends a 15" shaft. For our 11' 6" version, the manufacturer recommends a 20" shaft.

Mark

[44'cruisingcat]

We have a long shaft motor on a dinghy that only needs a short shaft. It still works fine. Sure draught is deeper than it might be, probably performance and economy suffer a little, but it's still OK.


If it's a real bargain, and you can't find a short shaft at a comparable price, the long shaft won't mean the end of the world.

[Terra Nova]

Yeah, if you are simply a lazy shopper, go ahead and buy the wrong size outboard.

[44'cruisingcat]

Jus thought I'd add some actual real-life experience. As usual it's not welcome on this forum.

[colemj]

A previous dinghy/outboard combo of ours also had a longer shaft OB than recommended for the dinghy. It ran perfectly with no issues for 14yrs - performance and economy did not suffer at all.

What people are not considering is that the difference in shaft length is only 5" - which is well within the difference in transom heights of varying boats. Anyone who has spent a lot of time with different outboards on different boats will understand that this isn't a big difference or exact match. In fact, a bit short is much worse than a bit long.

If the price was excellent and rare, I would go for that 20" also. At worse, you will just need to put a 2-3" riser on the transom (these are made specifically for the reason of more exactly matching shaft length with different transoms).

Mark

[44'cruisingcat]

Geez you must have been lazy and bought the wrong motor too!

[colemj]

In our case, the OP did.

Or rather, he was lazy and bought the wrong dinghy to go with the motor he already had.

Mark

[44'cruisingcat]

Me too. Bough the right motor for the previous dinghy, but when that needed replacing, we found a real bargain dinghy - ie brand new, 3.5m hypalon at 1/2 price - that had a short shaft transom.


Lazy shopper, wrong dinghy blah blah..

[txh2oskier]

Just looking to criticize whether it fits the facts or not? Go back and read my OP. I have a short shaft motor and was asking if my gut feeling about a long shaft was correct. I haven't bought anything. But no matter, you feel better for having shown your superiority.