Inboard to outboard conversion, need help with details.

[bradmc]

Hi

Some few questions concerning transforming an inboard into an outboard on a 90's galaxie 18ft bowrider.

I understand I will need a bracket. what kind of bracket do you guys suggest?
I heard of flotation brackets that hook right into the aft transom. Will these brackets be able to absorb the added aft weight on the boat?
Will the transom be able to hold 100 plus horse pounding on a bracket being held down by nuts and bolts?

Secondly, Patching the hull. Will I need to fibre glass the large hole left from the out board or will the bracket cover this?

Now for the weight issue. Once the inboard is removed, will it matter that the weight that once sat in the back, is now shifted back to the bracket? To supliment the difference can I add a large gas tank or just make-shift a heavy LEAD plate?

thirdly. I understand that outboards make the boat "hop" at low speeds, will this put strain on the hull causing it to crack?..or does it matter?

Thanks and I hope you guys can help.

The reason I am doing this is I have a 90 hp merc sitting in my garage. the boat is a project, and has no motor anyways. I might as well utilize the engine I have, rather than investing in a 6000 dallor crate inboard.

PS does anybody here know the max HP for a galaxie bowrider? I am thinking about trading my 90hp in for a larger engine and paying the difference.

regards,
Brad

[marshmat]

Start by contacting the coast guard ( http://www.ccg-gcc.gc.ca/ ) and requesting a (free) copy of "Construction Standards for Small Vessels" (TP1332). There's a lot of stuff in there that you'll need to take into account in your refit. The equations and curves for finding HP ratings are also in there.

I think you're right, a transom bracket is the way to go if you want an OB. There are dozens of styles that work, depending mostly on personal preference. The bracket is through-bolted to the transom with very big and hefty backing plates on the inside.

You will certainly need to patch all the old holes in the hull, and patch them correctly.

You will indeed change the overall balance of the boat considerably. It would be prudent to do a few pencil-and-paper calculations to figure out how much of a difference this will make (given the weights of the boat and the 2 motors, the location of the centre of buoyancy, etc. this can be estimated using high-school physics). The boat's behaviour will of course also change. However, I see all the time builders offering both sterndrive and OB versions of the same hull (sometimes V and jet, too); it's certainly quite a common change and the performance changes are a matter of personal taste.

About upgrading the motor: Larger is not necessarily better. A bigger engine is heavier, puts more strain on the bracket and hull, and drinks more squished dinosaurs. Try your converted boat with the 90, and different props, before you toss the engine in favour of a big heavy transom-monster.