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Inboard to Outboard conversion . Who Done iT ?!

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Inboard to Outboard conversion . Who Done iT ?!

Old 05-31-2020, 02:59 PM
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Default Inboard to Outboard conversion . Who Done iT ?!

I have a 1990 25 ft Steigercraft Pilot house boat . I hate the engine doghouse . would love to increase deck space . Can someone share some experience with swapping to an outboard ?
Old 05-31-2020, 03:25 PM
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that's an inboard/outboard or I/O not inboard. The biggest problem with hanging outboards on a boat like that is, the boat wasn't designed for it. The weight balance will be thrown off. The transom will need to built up to hold the weight and stringer reconfigured too plus a whole lot more. Not everyone who has done this project has been satisfied. You'll spend a lot of time and money on this project. Take a look at some of the other threads here. It's not a 3 month project. It's really expensive. Your best choices are live with what you have or sell it and buy a boat that was designed for outboard engines.
Old 05-31-2020, 03:57 PM
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There are plenty of hulls that came with both options. I happen to have a 25 Anacapri that was an I/O and I’m converting. Same hull was sold as an outboard. It’s a pretty good sized project if you don’t run into any other surprises like rot or delamination but could certainly be completed in a month working on it full time and having everything ready to go. Most likely though the project will grow as you find things that need attention. If you love the boat, you’re prepared and can find some positive info on your hulls running attitude with outboards I’d go for it.
Old 05-31-2020, 07:38 PM
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When converting a straight shaft in board to outboards , yes you need to do some weight redistribution.

But on an i/O... not so much. Theres almost 900lbs back there at least with a single v8 i/o and they are already in the stern. Not midship. But the rest of the boat may need to be reinforced. I/o transoms are cored just like an outboard boat
Old 05-31-2020, 07:47 PM
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Close up the hole and bolt a bracket on it.
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Old 05-31-2020, 10:48 PM
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X2...I closed up the hole and added a custom built bracket and zuke 250.
I now have 300 hours on it. It so quiet.


I sure love my outboard.

Old 05-31-2020, 11:11 PM
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Originally Posted by signmansez View Post
Close up the hole and bolt a bracket on it.
yes and please do it right. 1 layer of 6oz cloth with holes in it is not correct. The po rotted out the transom and I had to fix keyholes and put new transom in and put a proper bracket on.

my boat is picky on weight and ride but it was love at first sight.

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Rebuilt the outboard. Project is almost finished.
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Old 05-31-2020, 11:23 PM
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I will add that I had no rot; the transom was solid wood. After the conversion, the boat sat about 3 inches higher in the water.

Before the conversion

After conversion.
Old 05-31-2020, 11:33 PM
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Don’t take my post as discouragement. It’s a cautionary tale. Properly done you will have excellent results.

poorly done... well twice is nice as saying goes.
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Old 08-17-2020, 09:12 AM
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Go for it as long as you don’t mind spending the time and money. I did and the project turned out great. Do research composite materials and methods and err on the conservative side. Mine was a CC25 upfit to twin outboards. Did it with all composite construction and a on-off bracket. It will take the better part of a year to complete.
Old 08-17-2020, 09:46 AM
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Buy a outboard boat. It will be a lot cheaper than doing a conversion.
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Old 08-29-2020, 10:46 AM
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Default My Plan for conversion, your Progress

I would be interested in hearing your progress and pitfalls. I am also in the process of going from an I/O to twin O/Bs on a bracket. However, I can't imagine taking a year for the project as some have suggested (unless you are doing a major boat restoration).

I acquired a well used 242 Formula Sport Fish w/ a Mercruiser 260hp I/O. I am not a fan of I/Os in general and Mercruiser in particular, and since the steering pin and gimbal were shot (a common problem) I decided to install outboards on a bracket. My plain is very simple:

1) remove the I/O and motor (done and sold)
2) Inspect the transom (done and solid)
3) Glass in the hole (in progress)
4) fabricate Bracket (picked up aluminum yesterday)
5) hang a pair of old 2 strokes on the back (if the boat performs as expected, then spend 10x more for new motors than I spent for the boat)

I will admit that it would be smarter to purchase a bracket- but cost and shipping seems pretty high, and fabricating one sounds fun. I am still "engineering" the bracket. Currently the design is for a 24" set back and 40" in width. I have pondered engine spacing- after speaking to a charter boat operator than had widely spaced motors, he reported better maneuverability in swinging the boat in reverse, but cavitation problems in a following sea ( I assume slow trolling speed). If anyone has thoughts (or better yet actual experience) on motor spacing or set back issues- please chime. Thanks -Tim PS- if there is interest in keeping tabs on my progress, please reply and I will start a thread on the project. Thx
Old 08-29-2020, 10:58 AM
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check out the Steiger owner group page on facebook, someone just did this project.
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Old 08-29-2020, 05:56 PM
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I too had an I/O that we removed. The boat now sits 4" higher in the water and the trim line turned out to be perfect.
I had a custom built bracket from a well known highly experienced boat shop. In fact, he had 4 other boats in the yard, waiting for the modification. So I was very fortunate.
A drain plug access "cavity" was made, after these pictures were taken. We are 400 hours now on the new Zuk 250 that we bought out of Florida and shipped to WA. We are super happy.
Sixteen bolts hold the bracket.







Attached are some pictures of how it was constructed.
Old 08-31-2020, 11:09 AM
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Thanks Debit. How much set back do you have from the transom? It looks like the bracket is flush with the bottom and then tapers up toward the engine. If so, by how much? Assuming you put something bigger than the 9.9 on the boat. Did you raise the engine height any? Thanks.
PS- My project was slowed by weather. I was able to get the out-drive hole prepped for glassing in, and ground out the delamination I found on a few ribs- but can't glass when its 50f, rain, and blowing 35! -TC
Old 08-31-2020, 01:48 PM
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Pro-Line 251 getting some love...I/O to Suzuki O/B

750 hours. Completely satisfied!
Old 08-31-2020, 02:22 PM
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Alaska Formula - I included the pictures, since I thought you might benefit, working from scratch.. This boat shop mostly works on Alaska and WA boats. He is located in Mount Vernon.
They are "bay fishermen", and leave their boats up there.
Setback - 33" This is for a Zuk 250.
No, the bracket is flush and straight back. We had seen boats where it was not flush and did not like the spray.
Yes, we raised the bracket 5" since the motor is the 30" model. Water rarely some over the bracket, which I like a lot.
Weather here has been in the low 70s, and very nice. We were not allowed in Canada this year.

. The bracket rarely has water on it, as a result.

I'll add a picture of the inside view of the transom,

Old 08-31-2020, 03:19 PM
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Alaska Formula,
For steering and AP, we went with SeaStare and Si-Tex. My brother (a commercial tuna skipper) and I wanted APs that would hold a line, while fishing. We both chose the SP-110 auto pilot with virtual steering and like them very much,. It was easy to connect the steering helm to the AP power pump with 3 hoses, made in Bellingham. The AP price was remarkably reasonable.
Old 08-31-2020, 03:47 PM
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Default Small World

I too, fish in Bristol Bay. Years ago I had a shop in Burlington build a 32' Herring Skiff for me- North Sound., great builders. I can't recall his name now- but a great guy. I believe his son took over the shop. I have also had Ed over at Maritime Fab do a bunch a work on my Bay Boat. What shop did the work for you? I might know them.
From your pics, it appears they one-offed the build right on the stern of your boat. I am not that confident, I intend to mock it up in plywood first, cheaper than a mistake with aluminum. Thx TC
Old 08-31-2020, 04:08 PM
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Alaska Formula - the name is Petrselka. - brothers, and John does the aluminium stuff.
Yes - one-offed on the stern. My brother first had his little Lake Tahoe 19' boat done, where they filled in the transom and then added the bracket.

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