Can anyone advise me on how to work out the required shaft length on a deep vee hull when using twin outboards?
On a single engine set up its easy, measure from top of transom to bottom of keel and that's your shaft length. But how is the vent plate supposed to sit in relation to the hull when the hull is at 21 degrees from horizontal?
Do you put the vent plate level with the bottom of the hull on the centreline of the outboard, ie. half the vent plate is hiding behind the transom and the other half is in the water flow?
Obviously every boat is different and minor tweaks need to be made to get it just right but where is the start point?
I bought a pair of 225hp Optimax's for my Arctic 28 before I had the boat delivered. I went for 25" (XL) thinking they were too long, the plan being to mount them on jacks to lift them the extra 5". The reasons behind this were:
a) keeps the engines from getting swamped so much
b) allows me to close in the transom cut out so I don't get water spilling over into the boat so much.
Trouble is it's just dawned on me that this won't work! With the motors set back on the jacks by 5.5" and the transom closed in, the hydraulic steering cylinder etc. will foul the transom when I try and tilt! At least I guess it will, I haven't got the motors yet.
So I'm now looking at fitting the motors straight onto the transom and I've been trying to work out how much I may need to raise the transom height. Now that I've taken a tape measure to the boat, I'm now wondering if I have actually bought the correct shaft length and can just bolt them straight on!
If this is the case then I won't be able to build up the transom height to keep the water out but looking at the tide mark on the back, it looks like I have around 8" above the waterline which isn't too bad I spose.
Is this post getting too long?? Hello.....? Anyone one there....? Zzzzzz...
Ps. scanned a sketch I made of the transom, not sure how it will look when it's resized. And no, it's not to scale!