Sterndrive to outboard...jackplate or modified transom

Silvertriton · 15 August 2013, 00:20

Hi I am considering restauring this Ballistic 7.8 but I am not sure wether it is worth the effort and cost.... Obviously each boat will have its particular solution but as a general rule, when converting from IO to OB on a rib would it not be preferable to strengthen the transom with a steel plate and bracket to the stringers and a well rather than changing the center of gravity by fitting a transom bracket or which is likely to stick out at least 1" per foot of lenght? I also think that the transom modification may also be cheaper than fitting an external bracket. I am aware that some brackets have been specifically designed for some hulls and may add additional buoyancy but for the majority of RIBs this is not a viable option. Is a hydraulilc jack plate over a reinforced transom the best compromise?

http://www.flickr.com/photos/100273339@N02/9510953355/
http://www.flickr.com/photos/1002733...n/photostream/

Silvertriton · 17 August 2013, 22:08

Was my question too stupid or not clear or already well covered somewhere else?

PeterM · 17 August 2013, 22:18

maybe to tech for most members?

however there are some properly experienced members who may be busy at height of summer?

ncp · 17 August 2013, 22:24

Do a search here and on other forums. People seem to do this all the. I think that it's very boat dependant (transom construction) and after that, picking the correct style (jack plate versus flotation bracket). Some people have done Zodiac Hurricane conversions and Zodiac says to reinforce.

Good luck with it! It looks like fun project!

Silvertriton · 17 August 2013, 23:59

Many thanks Peter and ncp, I am quite ignorant on the subject and was afraid of not making sense...I have read several threads which talked about conversions but I guess that the brackets used by the Zodiac 733 while being perfect for that model may not be necessary for other ribs if a strenghtening bracket linking the transom to the stringer is built and an adjustable jack plate is fitted...again I am a complete newby to this and may be completely wrong...

Bigtalljv · 18 August 2013, 03:07

as one of the guys doing that very thing to a 733 now I would suggest looking to see i they made your boat in an outboard version. If they did then you know it can be done. I don't think they would vary the transom layup much but backing plates and such are generally very easy and certainly can't help. Are they still in business? A call to the manufacturer can be very informative. Fixing the hole is fairly easy even for the inexperienced. Just takes some plywood, fiberglass, epoxy, a grinder, and some sandpaper. That and hours of itchy work

Jason

Silvertriton · 21 August 2013, 23:24

Hi Jason, yes Ballistic have changed slightly the shapes over the years but they do mostly outboards now. i am trying to get the serial number to check with them more detailed specs. I have not yet seen the RIB since it is in a remote part of the country and I hope to have some better idea of its worth before going there in person...The current owner has just communicated that he has discovered that some of the fore deck ply stringers have rotten...I have asked him to test the tubes because if they also need immediate replacement it may not be worth repairing...

9D280 · 22 August 2013, 09:55

Quote:

Originally Posted by Bigtalljv

as one of the guys doing that very thing to a 733 now I would suggest looking to see i they made your boat in an outboard version. If they did then you know it can be done.

But bear in mind that even if they did both version the sterndrive transoms may have been built differently so may still need reinforcing......

Unfortunately I can't shend any light on your particular hull.

Dirk Diggler · 22 August 2013, 14:07

The most common reason for going the stand off box route is because you need somewhere for the powerhead to go when the motor is tilted up.

If you decide to go that route, be aware that your transom will only be 2" thick where the gimble was located, so you'll not only need to fill the hole, but strengthen the transom as well. I'd normally go with full height knees, bonded and mechanically tied into the engine/box mount bolts as well. 2 lengths of ally angle (12mm thick) is sufficient for that.

Bigtalljv · 22 August 2013, 15:30

A standard powerboat transom is usually on 2" thick so that shouldn't be an issue. The bigger issue is the rotten stringers. If they are rotten then it's a good guess that other stuff is too. Especially if the forward portion is rotten as the stern tends to sit lower and water flows downhill. if the tubes are good then the stringers and transom can all be replaced if you didn't want to use it any time soon. I'd drill some big exploratory holes in the transom and stringers before you make the plunge.

Silvertriton · 27 August 2013, 18:02

many thanks to all for the very interesting points. I am waiting for additional information from the seller before going a long way out to see this boat...I wil keep you posted of developments!