18sf transom angle

[jctj123]

Carpenters square wont fit to measure transom angle with notor installed on 20 in transom. Anyone have another technique to measure transom angle, or know the angle of a 75 18sf without a doubt? I've read thru alot and got many different answers. Prefer to measure myself without pulling motor.

[Capt Terry]

Not sure of your space limitations. Using a bottle jack could you hold a straight edge or carpenters level on the keel. Then using a small adjustable square placed on the level measure the vertical distance to where the square touches the transom and the corresponding distance along the keel. Hence the two sides of a right triangle. The angle would be the arctan of the short keel dimension divided by the vertical dimension. For instance the arctan of 2.9” divided by 10” is 16.2 degrees. Rusty on your trignometry, post a pix with dims. One of us will help.

[DonV]

Well you could get one of these, or a better one, get the keel level as in horizontal and check the transom angle measurements....bingo!

https://www.amazon.com/Johnson-Level.../dp/B00004T807

[jctj123]

I've got one of those. I'll use tongue jack to get keel level and put that on the transom

[gofastsandman]

Or a rock and a piece of string.

[jctj123]

I measured from the hull outside edge on both port and starboard side with carpenters square. I also measure as tight to engine on both sides. all three produce 3.75 assuming I have a 15 degree transom. would you guys trust this or do I really need to pull motor and measure off of keel? I measure many times between motor and the outside edge just couldn't get centered on keel.

[Capt Terry]

The old saying is a picture is worth a thousand words. I would assume the transom was originally planar with the same angle in all locations. Better confirmed by those who replaced their transoms and used methods to keep it flat. If you want the angle calculated via trigonometry, two dimensions are required like the height and base of a right triangle (the two sides that form a 90 degree angle).

[jctj123]

I understand the math and trigonometry just curious if the angle is different between keel to bottom of gunnel. wish someone who's done the transom bracket route on 18sf would chime in

[uncleboo]

Just sent you a pm. I used one of the cheap plastic dial type angle finders and it measured 15...I just don't know how precise it is.

[jctj123]

I'm now comfortable ordering my bracket for a 15 degree transom. Tongue jack as low as it would go got me to 1 degree of level and transom measured from center of keel and varies other spots was reading 16 degrees so with my 1 degree b4 level I'm confident with 75 sea raft 18sfbeing 15 degree transom