Angle of Prop Shaft to the horizontal for a Cavalier 28

Would anyone know the angle to the horizontal for the prop shaft for a Cavalier 28? Is it 8 degrees, 10 degrees, 12 degrees, 15 degrees, something else?

The reason I ask is that I will have to do some surgery to my engine beds. The engine beds should lie at the same angle to the horizontal as the prop shaft, to avoid unevenly stressing the mountings and bearings.

Why don't I just measure what is already there, or align the new beds with the old? I hear you ask. Because, at some time in its history, the builders or owners decided it was a good idea to put a step in the beds so that the aft mounts are on a step, about 70mm higher than the forward mounts (the rear bracket on the engine can be mounted up or down to let you do this). Not only is there a step between the front and rear brackets, but the steps do not lie at the same angle to the horizontal. There is, maybe, a 5 degree difference. So, I don't know if the front steps are right, or if the back steps are right, or if they are all wrong. If I knew the angle of the prop shaft, I could work something out.

There is not much of the prop shaft inside the boat from which to get an angle or an alignment. I'll measure it as precisely as possible, but it might not be very accurate.

Also, before anyone asks, the boat is not on the slips, it is in the water (else I could get a measurement). And, I've bought a polyflex coupling for the flange. I don't intend to rely on the polyflex to get things aligned, but it will increase the tolerances somewhat from the previous arrangement, which had the engine flange hard-bolted onto the prop shaft flange.

Someone here might know? Guess you have tried there. Would essentially need the original as-built plans.

www.cavalier28.com/

groups.google.com/g/cavalier28

Good move re the new beds set up and polyflex coupling.

To check the angle if there isn't much shaft length available inboard of the stern gland getting the angle of the shaft flange might be possible? Straight edge and spirit level used to draw a triangle on a piece of manila folder the calculate it?

I just use a dummy shaft made from bright steel shaft along with some bushes to centralise the shaft in the stern tube,,, like woko sugested

A level has limited use in boat building, setting up strong backs and moulds etc but when the vessel is in the water.... well it is variable. The plane you are looking for is an extension of the prop shaft, a builders square & string line taken off the prop shaft flange or a piece of ply with a factory corner should suffice. Then all that needs to be known is the engine mount offset from the crank centre line. This system is also useful in setting up universal joints that need to work in the same plane as their partner but can operate at different heights

Here's the challenge. The photo shows the starboard bed. The cardboard shows the main dimensions. The cardboard might be difficult to read because I traced the port and starboard beds onto it. The black lines (sharpie) trace the top of the existing beds, and the bottom of the cardboard aligns to the bilge. The thin blue lines show where I intend to put the new beds (maybe 15mm lower). You will notice that the two steps in the existing beds are not parallel. The existing beds are also too short. I think I will be able to cut in the new beds without puncturing the hull, but will need to work my way in carefully. My plan is to get some dressed hardwood planks, say 600 x 115 x 18mm (Tas Oak, or Meranti from Hammerbarn), over-cut the old beds, line up the dressed hardwood, and pour epoxy into the gap.

I'm currently making up some templates for the engine and flange.

(Channelling Leo and his Tally Ho project)