Shorten length of transom?

[iceangler82]

I just purchased an 89 Smokercraft deep v and a short shaft 15hp Johnson both separately. This is my first boat that I have ever purchased and I thought that it would be a good combination . After taking her out for a spin i realized that I should have bought a long shaft instead. Now that I am stuck in this dilemma I am wondering if anyone has trimmed a few inches off the transom to fit a short shaft engine. Any experience or thoughts would be greatly appreciated. 

[Dispy]

Neah neah..never......transoms are specifically engineered/designed for stress, thrust loads and carrying capacities. To alter it may be lessen the structural integrity of the vessel, especially if it is fiberglass.

[iceangler82]

Aluminum 14 ft.

[Dispy]

Aluminum 14 ft.

Curious as to 'how far' below the keel is the motor-centerline of the prop?

[tbfisherman]

I had a 1974 Johnson 40 HP short shaft and found out I needed a long shaft, so I had the motor coverted to
a long shaft.
Then I had the best of both worlds because if the need arose I could just swap shafts and take the housing
piece out and presto it was a short shaft again.
Back then it only cost me $150 Dollars to convert it.  [drive shaft and extension housing piece of the lower unit.]
Definately a better option then cutting the transom of the boat.

Hope this helps.

Bob

[Nor Easter]

I agree that converting is the better thing to do but it can be v-e-r-y expensive. A 15HP driveshaft alone could run $200.00 or more.
If the motor is anything from the mid 50's to the mid 80's vintage the job is a piece of cake. But your best bet is to find all of the necessary parts at a boneyard/used outboards junkyard.

Depending on the year, you would need:
Driveshaft
shift linkage extender or a longer shift rod
lower unit housing extension
bolts to fasten (probably 4 small, one larger but depends on vintage)
Outer cowling extension optional.
Labor to change it over and the parts could run around $500.00 but 1/2 that if you do it yourself or get an old timer mechanic friend to do it 'with' you.

Your best bet is to sell the 15HP as-is and buy another motor in long shaft version. But before you do this, are you sure you need a long shaft? A 14' rear tiller boat usually is set up for short shaft. Measure from where the motor would rest, down to the bottom. If it is 14 to 17 inches, you need a short shaft. If it is closer to 20 inches +/- 1", you need a long.

[Dispy]

Hmmm ...his first boat, so it is assumed a beginner boater. Therefore, before convincing him to buy a long shaft. How about asking the perhaps not so obvious question? What is the center line of your prop in it's 'lowest position below the keel?' Be sure to check your motor lock mount and that it is in the lowest position possible. If your vessel does not draft properly, make a slight adjustment to the pin setting, upwards. It is possible to simply measure your transom height to keel, the top of motor mount to centerline of prop shaft to determine if a long shaft is needed. Please find attached link, I suppose it is the best manner in which to make the proper determination http://www.ehow.com/about_6609738_short-shaft-boat-motor-definition.html

Good luck!!

[Dispy]

Not too mention that you ask but do not provide what length the boat is. RETRACTED you posted a 14 footer.

[tbfisherman]

He also mention the Boat was a Deep V...usually takes a Long Shaft Outboard Motor.

Bob

[Dispy]

He also mention the Boat was a Deep V...usually takes a Long Shaft Outboard Motor.

Bob

My Deep V hull uses a short shaft. To better gain an understanding of what should be used, please viewhttp://www.smalloutboards.com/shaft.htm

Only trying to help, based upon limited info.

[iceangler82]

I just got off the phone today with the manufacturer of my boat and they told me that they made it with both transoms. I took a trip over to the place that I am temporarily storing my boat and took the nesary measurments and realize that I do need a long shaft engine. Bummer! I then talked to a fella that owns a local boat shop and he told me that he has shortened transoms and gave me a few tips.  I have a guy that is really good with metal work and I am considering shortening the length. The engine is a 93 and after checking around it might prove difficult to find parts and someone to do the work. I'll try to post pics and give an update on either. 

[Nor Easter]

How about asking the perhaps not so obvious question? What is the center line of your prop in it's 'lowest position below the keel?' Be sure to check your motor lock mount and that it is in the lowest position possible. If your vessel does not draft properly, make a slight adjustment to the pin setting, upwards. It is possible to simply measure your transom height to keel, the top of motor mount to centerline of prop shaft to determine if a long shaft is needed.

Dispy,
I know you mean well but the top of the transom down to the keel does not compare to the top of the transom bracket to the center line of the prop. The comparison measurement on the motor is the upper inside of the transom bracket (where it rests on the transom) to the cavitation plate (which is designed to help keep air from entering the prop area). You seemed to be comparing apples to oranges...

Iceangler82,
You will lower the resale value of your boat if you modify it. Taller transoms are better than shorter ones because backwash does not splash in as easily. Please consider all of your options and safety before taking on the task.

[Moto21]

Just my 2 cents here but Id wouldnt shorten the transom. I work as a custom fabricator/welder with degrees in mechanical drafting and I'm a cert. mechanic and Id even look for other options first. Id personly look at some vertical jack plates and see if you could find one with the dimensions to work right or even have a custom mount for the transom made to lower it.  Really though the most logical awnser is sell your current motor and buy a long shaft.  Theres always good used motors in the classifieds and the price for a used one is most likely going to be cheaper then a custom modified transom job.  A lot more work goes into this type of job then most people think and time is money.  If you walked into my fab shop this is what Id tell you and send you on your way just so you would die when you saw the bill.  I think this would be your best option but thats my opion. Hope everything works out for you.
~Brad

[SWAMPGOOSE]

I have a long shaft on my 1954 15 horse and iam in realy shallow water all the time i built my trasom up higher with 4 huge bolts peace of wood and two steel plates looks like crap but it works great!!!!!! 1954 i dont realy care what it looks like as long as it works

[Dispy]

Dispy,
I know you mean well but the top of the transom down to the keel does not compare to the top of the transom bracket to the center line of the prop. The comparison measurement on the motor is the upper inside of the transom bracket (where it rests on the transom) to the cavitation plate (which is designed to help keep air from entering the prop area). You seemed to be comparing apples to oranges...

Iceangler82,
You will lower the resale value of your boat if you modify it. Taller transoms are better than shorter ones because backwash does not splash in as easily. Please consider all of your options and safety before taking on the task.

No offense taken however, both measurements directly correspond to one another. Moot point now anyways as he has found his answer.

Cheers & Tight Lines!!!