Underwater Gear

[Harry Babb]

What year model is your Express??

The strut looks like a fabricated strut rather than a cast strut.....I would not know if they are original or not........but the struts are not like the cast ones on my 1966 Express.

I do know that only a few 31's were equipped with intermediate struts like yours.

I'm guessing that your shafts are smaller than 1-3/8.

Harry

[Tony Meola]

I know on 75FBC, once had all the bottom paint stripped off the strut, they had Bertram stamped on them. It was pretty clear. I don't know if the older models were marked that way.

[Carl]

That setup does not look like mine either. As Harry said, it looks like a fabricated Strut. Looks to be a custom shaft log as well.

I never saw an intermediate strut on a 31 before, but I can say if the trannies are 1:1, I would understand why they went that route. If everything was not perfect the boat would rumble like a bastard. I was going to fabricate a pair of intermediates for myself, but then decided to reduce shaft speed with different trannies and that made a huge difference.

To answer your question, I don't know. From what I have learned here, Bertram came thru with differnent angles on the running gear. My Ol' 62 Express has a shallow angle that worked with a small wheel that was set up to spin fast using a 1:1 ratio, as reduction was added a larger wheel was needed and the angle had to be increased. So if your considering swapping the drive train over you have to see how your setup between the two. Take some measurements, shaft angle, shaft length, see where the shaft exits the boat and take it from there.

[Pete Fallon]

John,

The barrels on the intermediate strut bearings and main struts look like they have been replaced. My intermediate bearings have much thinner barrels, they are orginal from 1962 ( Made by Wilcox), I had new main struts cast by Buck-Algonquin back in 1995, they made the barrels thicker in case I went to 1-1/2'' shafts. The lenght from the bottom of the boat to the bottom of the strut barrel is 10". Low profile original.
The reason they put intermediate struts on is the early 31's had problems with shaft whip and snapped shafts. The were using 413 CID Chrsylers with direct drive trannies, the profile angle was lower( 13 degrees) and shafts were only 1-1/4" and longer. The props were only 16"x11 pitch 3 blades. They changed to 1-3/8" shafts in 1963 and went to longer main strut lengths that increased shaft angle and allowed for larger diameter wheels.
I changed my engines out in 1997, 7.4 Liter TBFI Mercruiser with Hurth 1:5:1 8 degree down angle trannies and 3 blade 17"x19 pitch props. 1-1/4" shafts. The top end speed went from high 20's to 41 mph and fuel burn was cut in half, boat cruises at 28 mph@ 3000 RPMS, 41.8 mph@ 4300 RPMS on GPS. The largest wheel I can turn is 18"x18 but I found that the 17"x19 with mediun cup works the best for my boat a 1961 express.
Good luck with your engine switch out.

[randall]

man....that must be fun to align.

[In Memory Walter K]

The i 1/2" shafts explain the intermediste cutlass bearing. That's why it's there.

[Carl]

Looks like they added a support pad from the log to the intermidiate strut, and then bedded the rudder flange.