Whaler Central - Boston Whaler Boat Information and Photos

Posted by phillips5281 on 03/10/20 - 12:34 PM

Hi all, I've been devouring this forum for the past few days in preparation of re-powering my 13' Whaler. The information here is amazing and from it I've decided to re-power from my old 25hp 2 stroke Mercury to a 30hp Tohatsu 4 Stroke.

I have the cut out transom (see photos) and from everything I've read my plan was to purchase the 15" short shaft. However in measuring the length from the top of the transom to the bottom of the boat it comes to 16 and 3/4 inches. I was of the impression that the cavitation plate of the engine needs to be BELOW the bottom of the boat but it seems to me with these measurements that it will be sitting above that point.

Has anyone had a similar scenario or could offer any helpful tips on wether this is going to be an issue or not?
Thank you!

Edited by phillips5281 on 03/10/20 - 12:37 PM

Posted by gypsmjim on 03/10/20 - 5:21 PM

In the olden days everyone believed that the caitation plate needed to be below the bottom. Then we started experimenting and found that there was a sweet spot that gave better performance, higher speed and lower fuel usage.

My 2017 Whaler came from the factory with the engine set 2 holes up. My 2019 SeaRay came 3 holes up. All of my previous boats were fine tuned by me and all had the plate ABOVE the bottom as well.

Posted by biggiefl on 03/11/20 - 7:26 AM

"I have the cut out transom (see photos) and from everything I've read my plan was to purchase the 15" short shaft."

Why did you cut the transom?

Posted by phillips5281 on 03/11/20 - 7:45 AM

biggiefl wrote:
"I have the cut out transom (see photos) and from everything I've read my plan was to purchase the 15" short shaft."

Why did you cut the transom?

I did not cut out the transom. I was just describing that I have the year model with the cut out transom. There were two different versions of the 13' Whaler, one with a transom straight across and one with a slight cut out as I have.

Posted by phillips5281 on 03/11/20 - 7:50 AM

Phil T wrote:
This model year has a transom for a 15 short shaft. Do not worry about the measurement.

Thanks Phil!

I had some worry because my old mercury was a short shaft and was mounted on an after market tilt & trim unit that hung off the back of the transom and made the engine sit even lower in the water than it would had it been mounted directly on the transom. With this setup the boat would cavitate pretty easily when trimmed up enough to raise the bow. But I also have my fuel tank under the forward bench seat so perhaps that was a contributing factor with the extra weight in the bow.

Edited by phillips5281 on 03/11/20 - 7:50 AM