Short Shaft Engine on 15-inch Transom

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
perkris
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Short Shaft Engine on 15-inch Transom

Postby perkris » Mon Nov 09, 2020 7:19 pm

In 2019 I bought what I think is a 1971 or 1972 Boston Whaler 13-foot hull as a project. This hull has the recessed transom "tub style"--that is not all the way across. [After restoration--see below--]now all I needed is a suitable outboard. Due the low transom I knew that the boat needed a short-shaft engine. I ended up buying a gently used Yamaha F20 with a 15-inch shaft.

Now--of course--I cannot bend the steering rod to fit through the tilt tube for steering.

I can install a U-flex steering clamp block on the transom, but in that case the outboard would not be able to be tilted as the thru-tube would get pinched by the outboard's thru-tube

I also think me cable is too long so I would need to replace the cable.

I could buy a 5-inch extension kit to the Yamaha (for $500) and install a jackplate on the transom.

I could buy a long shaft outboard and install a jackplate on the transom.

Geez I got the blues.

Give me ideas. I'd be very grateful if anyone has gone through this and has some good advice.


BACKSTORY:
The hull looked really fine but the deck and gunwales had tons of cracks. I decided to restore the interior. I gutted the interior wood. I [opened] the cracks [with a Dremel tool and] filed them with epoxy. Then I painted with epoxy primer, and finally [TOTAL BOAT brand] Wet Edge Whaler blue.

jimh
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Re: Short Shaft Engine on 15-inch Transom

Postby jimh » Tue Nov 10, 2020 7:41 am

perkris wrote:I can install a U-flex steering clamp block on the transom, but in that case the outboard would not be able to be tilted as the thru-tube would get pinched by the outboard's thru-tube.

I don't understand what components of the steering system you are calling "the thru-tue" that "would get pinched by the outboard's thru-tube."

A 13-footer with a notched transom for a 15-inch shaft engine is usually steering with the steering actuator link fixed into a clamp bracket on the stern.

Image
Fig. 1. A 13-foot hull with notched transom and mechanical cable steering. The steering actuator is clamped onto the transom, and the actuator rod connects to the engine steering tiller using a clevis; the clevis and its attachment to the tiller arm permit movement in two axis to provide for the engine to be tilted upward.

Image
Fig. 2. A 13-foot hull with notched transom and mechanical cable steering. The steering clamp includes a pivoting mechanism that allows movement of the actuator so the engine can be tilted up.

The alternative is to rework the transom so it becomes a 20-inch transom. This is discussed in a recent article at

A 20-inch-shaft Engine on a Classic 13
viewtopic.php?t=64

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Phil T
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Re: Short Shaft Engine on 15-inch Transom

Postby Phil T » Tue Nov 10, 2020 10:16 am

Having already sourced a short shaft (15") engine, I would work hard to obtain the proper clamp block kit and engine adapter plate as shown in the photos.

https://shop.hamiltonmarine.com/products/clamp-block-outboard-s-s--31760.html

Engine adapter plate = Many owners fabricate a plate in the shape of a T as shown in the photos.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

perkris
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Re: Short Shaft Engine on 15-inch Transom

Postby perkris » Tue Nov 10, 2020 1:12 pm

jimh wrote: I don't understand what components of the steering system you are calling "the thru-tue" that "would get pinched by the outboard's thru-tube."


I was referring to the tilt tube on the outboard [engine]. My [outboard engine] is set up for remote controls.

Can I remove the steering arm and attach the cable steering [actuator] rod directly to this point?

Or, will the same bracket as you have be needed?

My thoughts are that as the [outboard engine turns], this point swings in a radius and would perhaps bend the steering rod, unless the rod is not rigid on that plane.

Also when you tilt the [outboard engine], does the bracket pivot together with the [outboard engine]?

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Phil T
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Re: Short Shaft Engine on 15-inch Transom

Postby Phil T » Tue Nov 10, 2020 1:34 pm

The stand-off bracket on the rear wall has a pivot so the cable will rotate when the engine is tilted.

The attachment plate that connects the cable to the engine also allows for the engine to tilt.
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1992 Outrage 17, 1992 Evinrude 115

perkris
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Re: Short Shaft Engine on 15-inch Transom

Postby perkris » Tue Nov 10, 2020 5:14 pm

Thanks Phil - I will review the block and bracket option.

Has hydraulic steering [ever been installed on an older 13-footer with a 15-inch transom] as a solution?

jimh
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Re: Short Shaft Engine on 15-inch Transom

Postby jimh » Tue Nov 10, 2020 7:09 pm

perkris wrote:...when you tilt the [outboard engine] does the bracket pivot together with the [the outboard engine]?


Please read the caption at Figures 1 and 2 above to answer your question. [I have expanded the captions to further explain how rotation of the actuator and the link between actuator and engine permit some motion to occur--jimh.]

The boat shown in Figures 1 and 2 is not my boat. The boat shown uses the standard method for rigging a 15-inch-shaft engine on an older Boston Whaler with a notched transom.

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Re: Short Shaft Engine on 15-inch Transom

Postby jimh » Tue Nov 10, 2020 7:22 pm

perkris wrote:Has hydraulic steering [ever been installed on an older 13-footer with a 15-inch transom]...?


Considering that there are probably 100,000 13-foot hulls, I cannot say with any certainty if hydraulic steering has NEVER been installed on a 13-footer. Since there are so many hulls, it seems likely that someone must have done it.

perkris wrote:...as a solution?

Hydraulic steering is quite a roundabout way to solve the problem of the notched transom. For decades the use of a clamp bracket mounted to the transom has been a very good solution.

I think it is reasonable to point out that you are not the first person to try to run a 15-inch-shaft engine on an older 13-footer with notched transom and use remote steering. It has been done before.

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Re: Short Shaft Engine on 15-inch Transom

Postby jimh » Tue Nov 10, 2020 7:28 pm

The terms normally used in describing mechanical steering are:

--the engine tilt tube: a hollow tube to which a steering actuator can be mounted, with the steering actuator rod extending out the port end of the tube

--drag link: a mechanical link between the steering actuator rod and the engine tiller; the drag link may also include devices that permit some flexibility in the orientation of the tiller and the drag link connection to permit the engine to be tilted up.

--engine tiller: a lever arm that extends from outboard engine pivot to permit the engine to be steered, usually by a remote steering device

--the helm; a mechanical device that converts rotary motion of the steering wheel input shaft to a linear motion of a flexible cable output

--the cable: a length of flexible cable that transmits the linear motion of the helm output to an actuator rod.

--steering actuator mounting clamp; a device that mounts on the transom of 13-foot Boston Whaler boats with 15-inch transoms that fixes the end of the steering cable in place so the linear motion of the actuator rod can be connected to the engine tiller and steer the engine; these devices incorporate a ball-and-socket type joint that allows the orientation of the actuator to follow engine movement when the engine is tilted.

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Re: Short Shaft Engine on 15-inch Transom

Postby jimh » Tue Nov 10, 2020 7:31 pm

perkris wrote:
jimh wrote: I don't understand what components of the steering system you are calling "the thru-tube" that "would get pinched by the outboard's thru-tube."


I was referring to the tilt tube on the outboard [engine]. My [outboard engine] is set up for remote controls.


My confusion occurs because you used the term "thru-tube" twice to refer to different components. See above for some more standard terms used to identify components in cable steering rigging. The term you are using, “thru-tube", is not in common use. The more common term is tilt tube.

perkris
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Re: Short Shaft Engine on 15-inch Transom

Postby perkris » Wed Nov 11, 2020 12:02 am

jimh wrote:
perkris wrote:
jimh wrote: I don't understand what components of the steering system you are calling "the thru-tube" that "would get pinched by the outboard's thru-tube."


I was referring to the tilt tube on the outboard [engine]. My [outboard engine] is set up for remote controls.


My confusion occurs because you used the term "thru-tube" twice to refer to different components. See above for some more standard terms used to identify components in cable steering rigging. The term you are using, “thru-tube", is not in common use. The more common term is tilt tube.

Thanks Jim, English is my second language and I find when it comes to specific areas, such as mechanical or engineering terms, I do have a challenge.
I really do appreciate all your input - thank you.

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Re: Short Shaft Engine on 15-inch Transom

Postby jimh » Wed Nov 11, 2020 6:54 am

PERKRIS—thanks for the clarification on English as your second language. I understand more now.

Another term: CLEVIS—a mechanical attachment what allows for motion in one or two axis. More at

https://en.wikipedia.org/wiki/Clevis_fastener

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Re: Short Shaft Engine on 15-inch Transom

Postby biggiefl » Thu Nov 12, 2020 11:22 am

Many times you need to attach the steering to the engine and then install the engine on the boat.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).