Opions on shaft lengths

[ashedd]

I know outboard shaft lengths have been talked about since the dawn of time, but I'd like some input nonetheless.

I've got an 11' RIB/inflatable boat. It calls for a short shaft motor. I've used my Yamaha F8 shorty with success. I'd like to put a larger motor on it so it'll plane with more than just me aboard. I'm trying to make a little fishing rig to either sell or loan out.

I figure 15+ HP will be ideal. I actually found a well priced 35 HP Evinrude short shaft locally, but have since decided that 35hp is too much power, especially if I loan it out to people who might kill themselves with it. I'd also prefer a 4 stroke over a 2 stroke for ease of use for other people.

Found a nice 15hp short Evinrude 2 stroke that I might actually buy. A good running 2 stroke is a fine motor, especially an OMC. The only cheap(I'm cheap btw) 4 strokes I can find in the 15hp range are long shafts.

So the million dollar question is:
I measured my transom(yeah I know how to do it properly) at 18 inches, the F8 is also 18 inches. If a long shaft is "20 inches", can't I just used a LS and maybe use a piece of wood to jack it up a bit?

My second question:
Are there ANY long shaft OB's that actually measure 20 inches? The only LS kicker I've ever had was a Honda that measured 23 inches.

Seems like if I can get a LS that's 20 inches that it'll work for me. I don't want to use a commercial jack plate and have the powerhead of a LS sticking up real high looking silly. Plus they're expensive.

 

[ashedd]

EDIT to add:

The RIB is rated for 25hp at a weight of 120lbs. That 35hp I was checking out came just under 120lbs according NADA

Whats the actual shaft length of a mid 80's 9.9/15hp short shaft evinrude?

 

[jbcurt00]

EDIT to add:

The RIB is rated for 25hp at a weight of 120lbs. That 35hp I was checking out came just under 120lbs according NADA

Rated for 25hp, means rated for a 25hp.

 

[ashedd]

Rated for 25hp, means rated for a 25hp.

So what?

The question was, what LS outboard has a 20 inch shaft length

 

[jbcurt00]

So what?

Odd statement since you posted:

EDIT to add:

The RIB is rated for 25hp at a weight of 120lbs. That 35hp I was checking out came just under 120lbs according NADA

 

[racerone]

???----A short shaft motor is for a 15" transom.----A long shaft motor is for a 20" transom..----There is the same amount of motor sticking down below the hull in both cases.-------Yes you can use a stick to raise a motor up a bit.

 

[Sea Rider]

If comparing all OB's between them in same length say S or L shafts, will see that all are bit different in length, some are slight shorter, some slight larger, depends entire on OB manufacturer. You can mount a L size OB on a S (15-18 inch) height transom, for that will need to install a 3"- 5" SS transom mount that bolts right in middle transom.



If going by the wooden shim route will need a one piece large wooden shim glued and screwed onto middle transom along raising front and rear engine mounts for a solid height transom modification.

Happy Boating

 

[Sea Rider]

To illustrate two different S/L shaft OB's powering 2 different S/L boat's transom heights scenarios :



Right pic is a West Marine S transom Sib powered by a 2 strokes S 18HP Tohatsu OB. Lower leg being tad larger produces back or over transom water splashes at speed. By word of mouth of a shade tree boat guru, owner has added a doel fin on lower leg to compensate that issue. Wrong as seen on pic, West Marine transom is much shorter in height for Tohatsu OB to work as expected. Sib needs a transom height modification from current 37 cm height to 40 cm straight transom as same seen on red Sib.

Left pic is a Sea Rider S transom powered by a 2 strokes L 18HP Tohatsu OB, being way longer produced huge water splash over transom at speed, to solve that issue have duplicated same SS upper water deflector plate (>>>) Meantime is only roped to lower leg, once water tests to dial best plate height is reached will be screwed onto lower leg.



Tohatsu L 18 OB's have a large and clean lower leg, with a SS deflector plate can match any boat transom in the 15 to 20 inch height range. Now you know that S/L sizes different brands OB's and S/L sizes different brand boat transoms, most of the time will not match 100% spot on.

Happy Boating