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Author Topic:   1961 13 STANDARD Engine Shaft Length
19snooky63 posted 01-15-2015 05:24 AM ET (US)   Profile for 19snooky63   Send Email to 19snooky63  
[Some dimension of the] transom [of a 1961 Boston Whaler 13-foot STANDARD boat] is 17-inch. The anti-ventilation plate of the recommended short shaft or 15-inch shaft outboard will be 2-inch above keel. Will this affect performance? I am getting a 25-HP. Thanks.
macfam posted 01-15-2015 06:35 AM ET (US)     Profile for macfam  Send Email to macfam     
That's about right. You want the anti-ventilation plate ABOVE the keel, never equal to, or below. The best performance and control, and least porpoising occurs when plate is 1-inch to 2-inch above the keel.
jimh posted 01-15-2015 09:48 AM ET (US)     Profile for jimh  Send Email to jimh     
The transom of the older Boston Whaler boats is designed for outboard engines with a short shaft or 15-inch shaft. There really is not any particular dimension on the transom that is supposed to be precisely 15-inches.

Having an outboard engine with the wrong shaft length affects performance.

dg22 posted 01-15-2015 10:45 AM ET (US)     Profile for dg22  Send Email to dg22     
When measuring the transom, you need to take a vertical measurement. It should be closer to 15 inch.
jimh posted 01-15-2015 11:38 AM ET (US)     Profile for jimh  Send Email to jimh     
The vertical height will be shorter, but it won't be 15-inches on a transom of 17-inch height with the usual transom angle of around 13-degrees. It will be more like 16.5.

The trigonometry will be

vertical height = COS(transomAngle) x (transom height)

vertical height = COS(13) x 17

vertical height = 16.56

dg22 posted 01-15-2015 03:29 PM ET (US)     Profile for dg22  Send Email to dg22     

I read a post here that the actual transom angle of the 13-footer is 20-degrees. I borrowed my daughter's calculator and this works out to a vertical height of 16 inches using the formula Jimh provided. If I remember correctly that is close to what I measured a few years back.

19snooky63 posted 01-15-2015 05:39 PM ET (US)     Profile for 19snooky63  Send Email to 19snooky63     
thanx a lot folks you were realy helpful,i,m doing a total redo outside is buffed out,inside is blocked to 220,shold buff it out this weekend,came with orig brass and stainless,will post pics if I can fig it out,thanx again.

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