Borg Warner gearbox problem

[Jacob Vetter]

Hi fellow cruisers!
I have a problem with my Borg Warner 72C gearbox. It makes a big "klonk" sound when i put it in gear, almost every time. The shift arm has been correct adjusted, new gear oil, damper plate changed on the engine, but still it makes a heavy klonk sound. (some times it goes in gear smooth..) I am beginning to think it is the prop. I have an Autoprop (old) but ok. Maybe it is to big. Anybody have the same experience with that gearbox/autoprop?

[Foswick]

Well, it is not resistance. Resistance is futile.

[skipperpete]

Hi Jacob and welcome to the forum. Here’s a list of things I’d be checking to track down the “klonk”
1. Check idle speed, if idle is too high it may cause a harsh engagement
2. Input shaft splines worn. I know the damper plate is new but did you look closely at the shaft spline?
3. Output flange splines, if either of the splines ( male or female) on the gearbox output are worn, there will be a noise, maybe an oil leak too
4. Coupling to propshaft key worn out and coupling loose on shaft.
5. Propeller loose on shaft, again , worn key and loose on taper.
The last two on the list are the risky propositions, each of these circumstances can either lose the prop off the end of the shaft or lose the propshaft to gearbox connection and in some instances the rudder can be blocked by the shaft.
Is it a reduction gear BW or direct drive?

[Jacob Vetter]

Thanks!
You have a good point in output flange spline, they were worn when we changed the damper plate. I just now found out that the prop is also to big for the engine/gear/boat, so thats also a problem. I have a reduction gear, Borg Warner Velvet Drive 72C, gearing: 2.10:1

[deblen]

Some info on how to check Borg Warner fluid:
https://www.justanswer.com/boat/h2to...ive-fluid.html


Cheers/Len

[skipperpete]

Originally Posted by Jacob Vetter

Thanks!
You have a good point in output flange spline, they were worn when we changed the damper plate. I just now found out that the prop is also to big for the engine/gear/boat, so thats also a problem. I have a reduction gear, Borg Warner Velvet Drive 72C, gearing: 2.10:1

The Autoprop is by far the least likely cause of the noise on engagement, assuming it’s in good condition with no seized bearings or damaged blades. An Autoprop that’s “too big” is an interesting subject, Autoprops are self pitching so if the diameter was too large, theoretically it should adjust itself to the available power but I have no actual seatime with one despite having installed and re-raced the largest ( driven by a Perkins T6-354 with a 3:1 reduction) to the smallest, driven by hydraulic motors as part of a twin screw installation in a catamaran.