My transom on my Offshore measures about 15 inches from the top of the transom to the bottom not counting the outer keel. I have read that 15 inches call for a short shaft. Can I get away with using a long shaft on this boat?
Larry
Long shaft vs short shaft
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Phill Blank
- Posts: 412
- Joined: Thu Jan 05, 2006 4:20 pm
- Location: Hurley, Wisconsin
Larry,
Th problem with using a Long Shaft motor on a short shaft transom is that you will have the lower unit and leg deeper then they are designed to be and this can cause a lot of torque to be applied to the transom and you will drag bottom a lot sooner then with a short shaft.
I do not know what the handling would be like with the long shaft motor on a short shaft transom. It may be make a big difference or may not.
You may what to look at possibly raising the transom height to accomodate the longer shaft motor, which means rebuilding the transom and reinforcing it. Or looking aorund for a motor with the short shaft to fit your transom height.
Maybe some else has a better idea of what handling would be like.
Good Luck!
Phill
Th problem with using a Long Shaft motor on a short shaft transom is that you will have the lower unit and leg deeper then they are designed to be and this can cause a lot of torque to be applied to the transom and you will drag bottom a lot sooner then with a short shaft.
I do not know what the handling would be like with the long shaft motor on a short shaft transom. It may be make a big difference or may not.
You may what to look at possibly raising the transom height to accomodate the longer shaft motor, which means rebuilding the transom and reinforcing it. Or looking aorund for a motor with the short shaft to fit your transom height.
Maybe some else has a better idea of what handling would be like.
Good Luck!
Phill
If the egine is a Johnson or Evinrude, it is easy to convert back to 15", parts should be easy to find. Mercury has a one piece midsection and would take a lot more effort to make it a 15". Look on www.aomci.org for old parts.
The increased drag of the extra 5" would make the perforance bad compared to the proper length engine. If the boat was able to get on plane, you may see engine trying to oscilate from side to side, making driving hard at best.
The increased drag of the extra 5" would make the perforance bad compared to the proper length engine. If the boat was able to get on plane, you may see engine trying to oscilate from side to side, making driving hard at best.
Larry, to go from a long shaft to short you will actually be getting rid of some parts. You will however need a short shaft drive shaft and a short shift rod coupling. I believe that's all the new parts that are required. You will dispose of your 5 inch tower extension and one or two cooling tube extensions. As suggested post a question on AOMCI " ask a member" for an authoritive answer, once you know what you need post on the "webvertise" ads for parts wanted.
Joe B
Joe B
Good chance a 75 hp drive shaft will work. If you are lucky, the shift shaft will have a 5" coupler and all you will need to do, is find the std one. My 1960 40 has a 5" coupler on a std shift shaft. If not your will have to find a short shft rod, should not be hard.
Seems like some early 1960 75 had a extension on the drive shaft, can not remember if the 50's had one.
Post on aomci.org as Joe B posted
Seems like some early 1960 75 had a extension on the drive shaft, can not remember if the 50's had one.
Post on aomci.org as Joe B posted
Folks are always covetering long to short and short to long. So you can probably find someone to swap with in lieu of having to pay for the necessary items.
www.aomci.org discussion forum is the place to go.
Andreas
www.aomci.org discussion forum is the place to go.
Andreas