stuart turner

[maggier]

i an trying to install a p66 into my boat,the problem is its very tight to the keel with little room for manauvre, i have noticed on some photos of various engines that some of them have a dropdown gear box, is this unique to certain models or does the gear box fit all stuarts?

 

[Katouf]

A bit hesitant to reply 'cos my memory of Stuarts goes back to the 1960s!

The drop down bit you refer to is possibly the reduction gear fitted on the after end of the gearbox. Our P55MR had the 2:1 reduction (1500 rpm down to 750) driving a heavy wooden 22ft clinker hull on a 17 x 17 inch 3 bladed prop supplied by Stuart Turner. The gear box operated through a lever ahead and astern in the vertical plane (rather than the cute right angled handle swinging in the horizontal fitted to some of the smaller engines) and would have been connected, I believe, direct to the crankshaft. The lowest point on our engine was always the flywheel which was only 2 in from the keelson. This made for fun when there was more than 2in of water in the bilge! /forums/images/graemlins/smirk.gif The lowest point of the reduction gear was still higher than the bottom of the flywheel.

If you're tight for space and trying to fit with an existing prop shaft, you may have to consider using a universal joint (or 2) on the coupling in order to get the necessary height for the engine mounting.

Hope that helps in some small way.

Alan

 

[oldharry]

The standard Stuart gearbox was a 1:1 model with the output shaft in line with the crank, reversing being acheived by epicyclic gears, and cone clutches for for fwd and reverse.

A reduction gearing system was offered which was similar in operation, but had the 'drop down' bit you refer to housing the reduction gearing, which was in essence simply two gearwheels meshing with each other to acheive the reduction. The gearbox case was modified to accomodate the reduction gear, and from the diagrams I have the reduction gearbox casting was different to the standard gearbox necessitating replacement of the whole unit to change the ratio.

The reduction gear allowed fitting a large slow revving prop, while the 1:1 version normally fitted a 13 inch prop with a pitch between 10 and 12 inches depending on the application.

The cone clutches were quite vulnerable if the gear change mechanism was not correctly set up ensuring the cones engaged fully.

The other idiosyncracy of the Stuart box is that the rear oil seal runs on the casting of the coupling, and not on the output shaft as one would expect, which means that the shaft coupling has to be a Stuart.