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Catalina/Capri 25/250 Sailor's Forums

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Outboard Shaft Lenght

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JanS48
Navigator

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USA
141 Posts

Initially Posted - 01/12/2015 : 23:15:48

Greetings All
Boat: 82 FK Std rig.
Can I use an outboard with a 20 in shaft length? I see that many for sailboats are a 25 in length but told by others that a 20 is fine.
Comments please.

Edited by - on

islander
Master Marine Consultant

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USA
3992 Posts

Response Posted - 01/13/2015 : 07:25:09

A 25"(extra long) is best but a long(20") will work. If you are buying a motor I would target a xlong shaft engine. If the boat came with a perfectly good Lshaft then use it. I have a 20" Honda that came with my boat and although the prop will pop out of the water in rougher conditions it's not that big of a deal to live with. I put the mount fully down to stop this from happening and in 5yrs never had the engine come close to getting swamped. If you stay with the Lshaft then the mount can be fine tuned by removing it from the transom and moving it up to the last bolt holes in the mount. This will raise the engine some (1" or2") when in the fully down position thus positioning the engine at a better height. All this said, A 25" is still the best if you have a choice.

Edited by - islander on 01/13/2015 07:59:15

Stinkpotter
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Djibouti
9013 Posts

Response Posted - 01/13/2015 : 08:22:26

quote:
Originally posted by islander

...If you stay with the Lshaft then the mount can be fine tuned by removing it from the transom and moving it up to the last bolt holes in the mount. This will raise the engine some (1" or2")...

I suspect he means to move it down to the highest bolt holes, which will lower it...

The importance of a longer shaft increases with the length of the boat, since the issue is fore-and-aft pitching causing the prop to ventilate, momentarily over-revving, and losing power and cooling water. 20" is generally adequate on a boat up to 20-22'... But as Islander suggests, if you're buying new and are on anything larger than a small lake, most of us here will recommend dropping another "boat unit" or so for the 25-incher (as does Catalina Yachts in the owner's manual).

Edited by - Stinkpotter on 01/13/2015 08:26:31

islander
Master Marine Consultant

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USA
3992 Posts

Response Posted - 01/13/2015 : 08:42:11

quote:
I suspect he means to move it down to the highest bolt holes, which will lower it.

No Dave I mean raise the mount. With a 20" shaft motor using the second to lowest setting on the mount works only in totally smooth conditions so when things get a little rougher with wakes or waves you have to drop the motor to the lowest setting. Although this puts the prop low enough it's actually too low so to get it a little higher you have to move the mount up. The perfect setting for a 20" shaft would be about half way between the second to lowest and the lowest setting.

Edited by - on

Stinkpotter
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Djibouti
9013 Posts

Response Posted - 01/13/2015 : 10:26:51

Sorry... Of course! That was obvious!

Edited by - on

panhead1948
Captain

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345 Posts

Response Posted - 01/13/2015 : 11:58:11

Has anyone ever added a third notch between the lowest and the next position?

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islander
Master Marine Consultant

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USA
3992 Posts

Response Posted - 01/13/2015 : 12:13:36

That's a thought but taking this photo from CD it doesn't appear to be enough room between the other two to do it.

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 01/13/2015 : 12:46:34

So Jan, as you can surmise from above, placement and vertical travel of the bracket plays a large part in getting the prop low enough to maintain adequate bite in various conditions.

I achieved some additional depth by cutting off part of the lower starboard corner of my bracket. My cavitation plate sits about 1" below the water when the boat is at rest.

Someday, when I have nothing to do

I will explore an extension kit for my Yamaha 9.9 4-stroke.

Edited by - OJ on 01/13/2015 12:59:40

Stinkpotter
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Djibouti
9013 Posts

Response Posted - 01/13/2015 : 20:29:18

quote:
Originally posted by OJ

...Someday, when I have nothing to do I will explore an extension kit for my Yamaha 9.9 4-stroke.

FWIW, I looked into that for a Honda once... The evidence (and the dealer) suggested it would be cheaper to sell the old L motor and buy a new XL. The extension process involves a new drive shaft, a new shift shaft, a new exhaust pipe, the housing extension, and (in my case) the labor... and I would have ended up with an 8-9 year old motor. Instead I ended up with a much nicer model with electric start, automatic choke, high thrust, and maybe 20 more lbs.--all for a net cost of something line $800.

Edited by - on

Frank Law
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USA
159 Posts

Response Posted - 01/16/2015 : 18:47:30

I had a long shaft 8hp Honda on "About Time" I can't recall ever having the prop come out of the water . Any body looking for a 8 HP Honda pull start?

Frank Law

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.