That makes more sense now, always wandered why it was called brake horsepower as well, every day is a school day!
It may mean that I'm slightly underpowered with a crossflow but there seem to be plenty of options for tuning that engine if I find I need to increase power a bit plus I'd rather stay lightweight wherever I can. I'm loosing some weight in the build also as I've gone for fir frames, keel etc. The plans called for oak which would have made for a heavy boat!

Here's a progress report... With the other boat re-homed things are moving again
I've fixed the frames to the keel permanently this time, engine stringers are getting glued on tomorrow along with the sheer line battens. All the frames are screwed temporarily to the floor to keep them where they should be and everything seems to measure up correctly which is a good start. Here's some pics anyway...
And a speedy vid

Glad too see that the dog is "helping",,,,

Yeah she whittles pieces of wood from outside then brings them in for me... Not sure I'll be using any of them though

I'm after a bit of advice about prop sizes... I'm at the stage of doing a mock up for the prop shaft angle (thanks sean-nós for the pic). But the thing I'm unsure of is what size prop to cater for? I'm going to make a p-bracket so the drop is pretty flexible size wise.
The engine I'm using is a 1500 pre crossflow, I'd appreciate advice / comments or even to know what others are running with this engine would be great! Obviously it will take some tweaking once the boat is running but I don't know where to start as of yet

I had to mount the engine and gearbox first as you want it as low as possible and it can depend on where your sump and gearbox hit the bottom of the boat,the distance between the rudder and the engine allowing about 4" to remove the prop and 2" between the top of the prop blade and the hull I also off set the rudder about 1/2" so the prop shaft could be removed without removing the rudder.
Once you have your engine angle you can work out where your strut and prop will go on paper "I used wallpaper backing paper"




Making sure you take into account the thickness of your hull and if you are going to sink in the strut to keep it flush.

Before anyone asks Dan will be running a 1:1 gearbox.

so if your prop is 13" diameter and you need to clear the hull by 2 inches would that make the drop at the back end of your strut about 8 1/2"?

I'm thinking I might build it so I can fit up to a 12" diameter prop or maybe even smaller? So could I make the drop about 8" at the strut to suit that? If that makes sense

Thanks Alacrity yeah gearbox is 1:1

I'm running a borg warner 1-1 gearbox and I had to cut a bit off the mounting plate to get it down to 12%, you also have to try and keep the engine as close as possible to it's centre of gravity and centre of buoyancy as any movement in a small boat can upset the balance a rudder off the back of the transom will give you a bit more room to play with. I made some mockup struts and using some 1" hollow steal pipe fitted to the gearbox I was able to work out where to place it.

Dan, take a look at a Delta prop with the same engine (like mine) - that will give you a reasonable starting point. Not sure how your boat weight will compared to a Delta which is a light boat (although not with me in it!). You may be able to borrow one to use to mock it a up. Even an Albatross (Kent engined version) will do as it will be the right dia - albeit the reverse rotation but that won't matter just now.