bertram31.com

Hey Guys,

Anyone know what the stock down angle on the 1 3/8” shafts & struts is? I’m not at the boat and need a quick approximation.

Thanks,

JohnV8r

Not 100% sure but I think its 15 degrees.

Thank you!

Don't take that to the bank. Somebody who actually knows what they are talking about likely will come along shortly.

John

What year is your boat? I don't remember the year but at one time some of them had 12-degree shafts.

John

I found this from an old 2020 post. Maybe Carl can confirm since he was the one who stated the 10 degrees.

the 31. The stock 10-degree struts from what I know are for 1-1/4" dia shafts with no room to bore open for larger bearings. Then they only have ... point just yet. What I can say for sure...the closer the shaft/prop angle to the direction of travel the more efficient the setup. Outboards ...

1978 FBC. 1 3/8” shafts.

Older boats running 1:1 trans on gas motors with 1-1/4 shafts had short, sleek 10 degree struts allowing a 15inch wheel. These struts had no beef to open for larger shafts.

The others had the longer 15 deg struts allowing the boat to turn a more efficient larger diameter wheel. These came through with 1-3/8" shafts to handle the extra torque. The barrel holding the Cutless was also kinda beefy so most struts could be machined open a bit to fit a larger Cutless bearing opening the door for 1-1/2" shafts.



If your not sure...your wheel size will tell you. A 16" diameter wheel left a prop tip to hull clearance of aprox 3/4", so if your running a larger wheel, it's not the 10 degree strut.

John mine is 1977 and stock was 15.2deg with 1 3/8” shafts

John

You would have the 15 degree shaft angle.