Vetus Bullflex coupling

[lockie]

I can replace the Polyflex flexible disk in my existing coupling and hope for reduced vibration, or I can spend 3 times as much on a complete new Vetus Bullflex.

I have accurately aligned the existing coupling, the shaft has been checked for true and the prop is fine as are the engine mounts (only done about 150 hours.

I'm interested to hear from others as to the worth of the Vetus coupling.

Cheers, Graeme

[skipperpete]

Hi Graeme
A Uniflex 13 or a type 6 are both preferable to the heavy and large Bullflex they’re all pretty good flex couplings but the bullflex is really heavy duty commercial.
What engine do you have? Is there any runout on the polyflex disc?
What’s the shaft diameter and speed?

[lockie]

Pete;

Thanks for your response. My bad, I should have made it clear that my engine is a 13hp Yanmar 2GM, for which the small Bullflex is the closest rated. The others your refer to are for much higher power applications and would hence be much stiffer.

[GordMay]

Originally Posted by skipperpete

... What’s the shaft diameter and speed?

Per Vetus:
Which Size Bullflex Coupling do I need?
The calculation is fairly simple - to determine the HP/100 r.p.m ratio figure the equation is:
(Engine HP x 100) ÷ The maximum speed of the propeller shaft*.
Vetus Bullflex flexible Coupling Type 1, shaft Ø 1"
* Depends upon engine RPM & gear ratio.

[lockie]

Yes thanks Gord, selecting the right Bullflex is straightforward, but I guess what I want to know is whether the extra cost provides much reduction in vibration compared with a Polyflex-style? I'm hoping there is someone out there who has done such a swap and can share their experience.

[Searles]

Sounds like the engine might be ideling to slow ,needs to be above 800 rpm ,if all is good ,as in the motor condition ,slowly increase the idle until smooth .��⛵️⚓️

[skipperpete]

I ordered a bullflex for a 2”shaft and it duly arrived at the boat. Not only was it too heavy for me to lift, it was also too large physically to fit in the space behind the gearbox so a disaster all round. I never read the vital statistics.
Even the smallest one weighs 3 kg but at least its only 100mm diameter.
So I never got to try the bullflex BUT I did use a uniflex to resolve a problem with a 1° angle error in a new installation, yanmar don’t allow the front of the engine to be below the horizontal and the only easy way out was the Uniflex, it worked out very well but I initially had my doubts.
Pete.