I/O to Outboard conversion question

[soaked]

I have read the other posts on this topic and have been thinking about this conversion for my 1979 Carver 23' runabout. It's powered by a mercruiser 260 - which I am tired of always working on. I would likely replace the 260 with a 250 outboard, but those suckers are 600 lbs, plus change.

I was thinking that the transom repair and new bracket for that large of an outboard would be strongest when tied into the existing I/O engine stringers, but am not sure how that would work... seems like the stringers support weight applied from above, not cantelevered and attached from behind.

Anyone have any thoughts about conversion of such a large power source?

I understand the basic reluctance - especially since an I/O transom is not built for a large motor to be hanging off the back... Although, it is a very common practice up here where I am (SE Alaska). And, I have access to good aluminum fabrication services as well as folks who can repair fiberglass... sadly, I just don't have access to a good I/O mechanic.

Yes, I know the cost difference is extraordinary. I also know that an I/O engine compartment is just a potential puddle in which your engine will eventually take a bad swim... And dang if changing the starter isn't a serious chore!!! And the engine cover is always in the way when hooking up a big king, or trying to land a big pooner halibut...

Thanks for your thoughts.

 

[mattsmall1972]

Re: I/O to Outboard conversion question

I'm doing the same thing on my 1970-something Sea Ray 240 Sedan Bridge. I'm planning on a single outboard bracket that has angle iron arms attached to the inside bolts that connects to the motor mounts, thus providing support to the top of the transom - similar to a knee brace. When I get to the point of rebuilding the transom, I'm either going to use Seacast or have at least 2 inches of transom thickness for added strength. Also, I'm planning on putting knee braces from the stringers as long as they don't get in the way of the angle iron brackets.

Hope this helps.

 

[Reel Kahuna]

Re: I/O to Outboard conversion question

Your 23 footer should handle a 250hp motor just fine. I mounted a Yami 150 on my 20' which pushed the boat fine but I think I could have gone as much as a 200hp. I'd suggest having a Gil Bracket made that'll provide floation that' literally will be an extension of your hull. By making brackets only will transfer lots of stress to the bolts rather than spreading the load. Stiffeners inside the boat attached to the stringers strength the transom. Some will say it's not needed but for peace of mind, I put stiffeners made of plywood encased with fiberglass.

I posted pics of this before but rather than doing a search, here's the pic again of the Gil bracket. BTW I also mounted my motor onto a power CMC jack plate. I was able to see and feel the difference when trimming the jack plate while underway.

The only issue I had was getting the proper prop. I bought the motor used and which had a 20 that only brought my WOT to 3K rpm. I bought a 17 that raised it to 4900-5100rpm. WOT on the Yami should be 5500-5600 so I ordered a 15 which should be delivered next Tuesday. I could have lived with the 17 but figured to do it right .

Here's a pic during the shakedown cruise.

 

[soaked]

Re: I/O to Outboard conversion question

Thanks for the replies.

I was planning to mount a gil bracket like the one in your photo, RK. There's a local guy who can weld one up for me. I also carry a small kicker, so will need a wider bracket. I was trying to figure out if that gil braket would then be further secured through the transome to the stringers, with something like the braces or the angle iron brackets that Matt mentions. I am guessing the brackets are mounted flush to the stringer.

What is a knee brace?

Good tip on adding thickness to the transom - marine ply, maybe even glass it. Peace of mind is big when fishing with the family.

If either of you happen to have pics of the old engine compartment in the finished state, I would love to see them.

 

[Rich Hargis]

Re: I/O to Outboard conversion question

I made a plate that had the same bolt pattern as the Armstrong bracket,the plate was through bolted into the bracket.I then took 2 pieces 4x4 angle (approx.30") and butted one end up against the inside plate on both sides.Then I drilled the holes into the stringers and put some 5/8 bolts through them.Next I took some 2x2 angle and made them to fit from the top of the plate to the other end of the 4x4 angle on the stringer.This creates a Knee brace (Approx 45 degree angle) I tack welded everything together and pulled it back out.I drilled out the holes larger in the stringers so I could epoxy a fiberglass sleeve into them(Rake handle). I traced all the parts so that I could have it fabbed up in stainless steel later.In the mean time I finshed welding all the parts together and painted it with a good epoxy paint and slapped it back in the boat.I first had a Yamaha 2 stoke on it until it blew up.I am now running a Suzuki 4 stroke and love the whole conversion that I did to the boat.
Here is the thread

http://forums.iboats.com/showthread.php?t=262606&highlight=Wellcraft

 

[Reel Kahuna]

Re: I/O to Outboard conversion question

Hey Rich, I just clicked on your conversion thread. Great work!!

 

[Rich Hargis]

Re: I/O to Outboard conversion question

Thanks, It was actually fun. I would love to find a 28 or 29 footer and do it again.