Seafari with OB in well

[rockdoc]

Here's an idea that occurred to me yesterday. I sold the V-6 and drive out of my 1974 Seafari and am thinking; OB? OB on bracket? OB in a well???

I've been looking at the Simmons Sea Skiffs for years, and recently the Atkin Ninigret ; both great looking boats with outboards in wells. I'm just wondering out loud here; what about hanging a 90 or 140 in a well where the i/o motor was in the Seafari. I realize this would move the prop forward a foot and half or 2 feet... But center of gravity would be forward too... I just might try. Any ideas?

Steve

[Bushwacker]

Steve,

Building a well for the motor is certainly more work than a bracket, but the boat would definitely be better balanced with it and you'd save some weight. A couple of years ago, I asked Carl Moesly how the CG compared between the I/O and OB configuration. He said it's further forward on the I/O, even with the very light outboards they had back in the 60's! Although the I/O weighs a lot more, most of the weight is forward of the transom. That confirms my experience because I know the I/O Seafari rides better and will plane at a lower speed than the OB model

What you're proposing should give you a CG similar to the I/O, but with less engine weight, and much less weight than a bracket. The bracket might give you a 2-3 increase in top speed, but my experience is that it will hurt the ride and increase min planing speed. Once you add a 4B prop and an AV plate fin to correct those problems, top will probably be LOWER than it would be with a motor on transom!

If you put a compact low profile motor like a V-4 E-TEC in the well, it would probably fit under your existing I/O engine box, so you would end up with a full height splashwell too! The only problem I can see with that is that you'd have to check the tach to be sure motor is running, since you won't be able to hear it! Denny

[rockdoc]

I'm really thinking about trying this. Thinking outside the box here; actually, inside the box......
I don't love brackets, and I do love closed transoms. The noise reducing factor of an outboard in a well with a lid is a real plus too. Nice casting platform as well.

Steve

[pianewman]

Very interesting thread. I just can't envision where the engine would come through the hull, how large that opening would have to be, how/where you'd run steering/shift cables, how the engine would be attached to the boat.
Am I missing something here, or am I just too stupid to see how this would work?

[Blue_Heron]

Originally Posted by Bushwacker

What you're proposing should give you a CG similar to the I/O, but with less engine weight, and much less weight than a bracket.

I would tread with caution here. You're not only talking about the effect of a lighter motor moved forward affecting CG, you're also talking about reduced dynamic lift where you cut the notch in the keel to accommodate the forward mounted motor affecting CL (center of lift).

Maybe the two factors will balance out, but I wouldn't go down this road unless I knew the answer to the CG/CL question before I started. If you can afford to have a naval architect run some numbers for you (I have no idea what that would cost), that would give you some assurance of success. If not, the bracket and transom mounted outboard approaches are well documented.

Not trying to discourage you, it's a novel idea. But you should know what you're getting yourself into. I went in blind on my 25 Seafari and got lucky. But there are some things I'd have done differently if I'd done more research first.

Dave

[rockdoc]

Well, I have a 20 Seafari I'm basically going to keep and re-do the transom on to hang an outboard, give away, or do something interesting with....... I'm not too worried; I have enough backyard naval architect in me to get this to work....

Steve

[Bushwacker]

Originally Posted by Blue_Heron

I would tread with caution here. You're not only talking about the effect of a lighter motor moved forward affecting CG, you're also talking about reduced dynamic lift where you cut the notch in the keel to accommodate the forward mounted motor affecting CL (center of lift) . . .

Good point on the CL change Dave! The notch would remove several sq. ft. of planning surface, so even IF CG were unchanged, that would still reduce stern lift that helps low speed planning! Might be able to compensate with other stern lifting devices like trim tabs, 4B props and AV plate fins, but then you're back to needing the extra stuff you'd also need with a bracket! Might still be a bit lighter than a bracket, although I could see the sides of that tub being about 1.5" thick with some big knees on motor mount surface to transfer motor loads into the stringers and existing transom! I started reading Dave Gerr's book on Boat Strength but still have a long way to go! Denny

[rockdoc]

I have considered the loss of planing hull surface. I do have a set of Bennets waiting for an assignment.....

[rockdoc]

I'll have to take a look at Dave Gerr's book.

[pianewman]

Okay, now I understand a bit better. I was wondering what would happen if you removed planing surface at the transom on such a short boat.
Thanks for the discussion, guys. Very interesting.