Propeller query

[Dmc]

I have been in touch with Broom and they confirmed that these are correct sizes as fitted when built.
Thanks to everyone for your input and suggestions much appreciated!

 

[snowbird30ds]

A friend of mine had a coronet 30 with a pair of md32's and the ratios were different as one box ran in reverse to give counter rotation so had odd props to suit, it always ran even and well and were original props.
With 4108's likely to be same era.

 

[Bilgediver]

Need to know the gearbox ratios .... need to know if they are the same or, as suspected, different

Might find a few Broom 30 owners on The Thames forum.

 

[scottie]

What make of gearboxes?

 

[Spirit (of Glenans)]

Boat may have had replacement gearbox at some time in its life, for reasons of budget or availability the drive ratio may be different from original box.
Simple check.
Go at WOT on each engine separately , if they achieve roughly the same revs, they are probably OK.
If vastly different , really depends as to how much faff and expence you want to go to to sort it.
A decent local prop shop can tweak the prop blades but at around £100- £150 .
Guess from prop pitch its a slow displacement boat.

WOT...... wide open throttle. I had to google that!

 

[QBhoy]

If broom say this is originally correct, I’d assume that when new, they achieved counter rotating props by means of reversing the transfer through the gearbox on one of them. Not ideal and a little cheeky, but a method of doing it for sure. If I’m correct, it would mean that one engine is running through what would normally be the reverse gear ratio. If I didn’t read above that broom suggested it’s original, I’d be doubtful this was normal