All about shaft lengths and mounting methods

Posted by Carolien Henn on May 9, 2023 8:16:30 AM


An outboard motor is the most critical choice you can make when it comes to power for your boat. It is important that you not only have the right size outboard, as discussed in our blog the right outboard for you, but that you also have the correct shaft length and mount the engine correctly.


Why is this so important? 

Having the cavitation plate of your outboard too low will result in additional drag in the water which may affect the performance and fuel consumption of your outboard motor, especially at higher speeds.


To start the process, you need to measure your boat to know what the perfect match will be. Ideally, you want the outboard's cavitation plate to be at the same level as the bottom of your hull.

To measure your boat, you measure from the top of the transom to the bottom of the hull, thus straight down to the lowest point of the hull.


This will determine how your outboards will be mounted. The way an outboard sits at the back of your boat depends on the mounting method, in other words how the transom has been designed. Does the outboard hang from the transom or is it fitted to a mounting bracket. 


Direct mounting

When mounting the outboard directly to the transom of your boat, measure from the top of the transom down to the bottom go the hull, the lowest point also known as the keel.


Transom brackets 

Transom brackets are often used on bigger and seafaring boats to offer maximum protection against bigger seas since they have another advantage that they often allow boats to use standard-length outboards.

With the bracket in the down position, measure the top of the mounting surface down to the bottom of the hull. 



Now we look at how you can tell the shaft length of your outboard motor. 

The shaft length is measured from the bottom of the mounting bracket where it will rest on the transom to the top of the cavitation plate. (Please see the image)

Screenshot 2023-05-09 at 08.38.59



Our outboard motors come with three different shaft lengths, 15 inch (short), 20inch (long), 25 inch (extra long) and 30 inch (extra extra long). Measuring your transom height will likely provide a height measurement between 14 and 32inch. 


Contact your closest Suzuki Dealer for expert advice in this field. 


Happy boating!


Topics: Aftersales Service, Technical