why do they tie outboards lower unit with rope? in racing outboards?

i can understand that but
-is it necessary? or just an additional action?

Helps reduce stress on the motors and transom. Is it necessary? I don't know, but why wouldn't you use them for the extra support for the motors? I wouldn't say it is overkill.

Tim just looking at a Mercury 2.5 you will see that the way the trim ram is mounted (vertical with the pin at the very top) that the propeller has a tremendous mechanical advantage….

Theoretically if cylinder/cylinders were mounted lower (maybe midpoint between the tilt tube and gear case) and in a horizontal position much more of the thrust loading and unloading could be assumed and dampened entirely by the hydraulics. And the need to Bungee the lower unit to negate any oscillation would not be needed!

Most of the darn outboard trim units use little pusher pins to trim the motor out. A good pull will let the motor flop up a good bit (as the tilt ram pulls out, the little trim pushers go in due to the way the hydraulics are setup.

This allows the motors to pop up if you hit something.

Race-only motors on race tunnels and such use a single center ram mounted to the gearcase as you described. They won't even TILT up all the way, they need will only trim up and down thru a given range.

If you run this setup, you don't need bungees, but with a normal setup it's a good thing to keep the motors pulled in against the trim pushers.

Check out the white bungee cords on this monster.......

Twin Johnson V-8's on a 26 Velocity!!!

Sorry had to resize.......

Those are spare starters, if your original one don't work, ya just take one of those off, wrap it around the flywheel and give it a good jerk, and presto, your up and running again.

You also sometimes see bungies off to the side of the motor. This is to help take some of the torque off the helm.

Spectre,

Good point. I've never been able to figure out how to "rope start" a big block, but I've yanked a 2.5 Merc to life more than once...