Tunnel hull with outboard

[GeoffSChapman]

I have a bare 7m50 hull with a tunnel, designed for an in-board diesel drive, I would like to fit an outboard moteur, is it worth the effort modifying the hull to remove the tunnel?
I would imagine that if I place the prop in the area of the tunnel it would be ok

[safewalrus]

You could drop the prop in the tunnel and it would work but you'd most likely lose the manouvering ability of the outboard and it's swivel prop!

I guess the best and most reasonable way would be to put the prop in position in the tunnel and try it with a normal rudder, if it don't work then you can start ripping the boat apart but it seem's a bit drastic! (another good thing with the outboard is it would be easy to remove it for maintenance!)

[GeoffSChapman]

I was thinking of fixing the moteur on an outboard bracket about 80cms aft of the transom would this retain manouverability?
In other words the question is what do I loose by keeping a tunnel when it's not necessary?

[War Whoop]

Is it a prop tunnel, a full length wet tunnel or a dry high-speed tunnel design???

A clue to start would be on an outboard motor as a rule only the lower unit is shaped to run through the water if there is any midsection exposure that should be addressed with a long faired in Deflector/Pod/Appendage/Blister wide enough to protect the exposed portion of the engine and tapered in at it’s foreword portion. Like we do on the three engine boats where the center motor is in the tunnel.

in this situation, he might be best off with his outboard mounted on it's bracket, with a bob's machine shop, jackplate - allowing him to raie or lower, the outboard so that the prop and water intake / anti vent plate, are located within the optimal poisition with regard to the tunnel of water exiting the transom tunnel?

I suspect that far from losing maneouverability - he will gain much over the original shaft /prop /tunnel / pocket installation...in terms of maneouverability, reduced draft, increased speed and so on.

Just do it - I can't see any need to start messing with the underwater shape of your hull.

Cheers!

[GeoffSChapman]

Thanks for your suggestions,
I'm going to give it a try, and outboard on an adjustable bracket, I'll let you know how it goes.
Geoff

[safewalrus]

Yep, seems the best way to go! I certainly wouldn't mess around with a perfectly good hull if I didn't need to! Can't see you having to much of a problem with the motor on the back of the boat. Best of luck but I don't think you'll need it!