Switch from I/O to twin Outboards

[CaptainQ]

Hello I am new to this site and my name is Michael and boats our my passion. Question i have is the Boat is a 1990 Switzer 22.5 or 23 lol . im thinking of converting over to twin 200 outboards. The questions i have are .....

What kind of reinforcing would need to be done so it supports twin 200-250 HP outboards

Any one have a twin outboard bracket used for sale that's decent but not crazy expensive


Thanks for the help by the way !


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[Capt.Insane-o]

https://www.screamandfly.com/showthread.php?333057-25-Checkmate-Convincor-I-O-to-twin-O-B-s

[CaptainQ]

https://www.screamandfly.com/showthread.php?333057-25-Checkmate-Convincor-I-O-to-twin-O-B-s
Thanks yes i seen that long thread lol. Alot of good stuff to see there.

[johnmiffco]

most single engine i/o boats were built 2 ply thick just at the gimble and that inner transom pic looks to be as stated
just 2 ply in center and single on sides
so not strong enough for o/b bracket being thin and the 2 low braces
to be right and safe id be putting in a new transom double across the whole rear
and big brace boards up high by top cap and longer along bottom to be able to hold all the weight of the motors and bracket
and mainly not flex or break off in rough water,,,,,

[CaptainQ]

Thanks for looking at pics, the center is twice as thick and has those small supports. I was looking at that checkmate thread and seen what he did but did not know if my transom was enough. What kind of wood would you use or would you layer glass and balsa or something like that.
See the whole thing is the boat came with a king Cobra 460 set up and I don't know anything about OMC other then people say get rid of it. So if I am going to go through all that A twin outboard boat is what I really want. Let me know about the wood. Thanks

[johnmiffco]

saw ur thread on OSO
and agree with every1 that replied
omc parts are scarce and bravo is cheap as boats being parted out and used bravos are everywhere'
as far as transom can rip it out and go back with wood,,,3/4marine plywood,,,,layer glass1ply layer glass 1 ply
build all the braces and 2 layers glass over all
there also is lots of new composites to use to last forever
done right and sealed marine ply good for 20yrs
also that lil switzer is a good candidate for twin o/bs
I wouldn't use a big 12-24" platform standoff box
short boat would be bow light for rough if set back too much from motor weight hanging way back there
2 good 4-6" jack plates would do

[CaptainQ]

Thanks for the Info John. I think I might try and sell the motor, maybe it would sell quick. I would have time to do the outboard conversion and still have a boat for summer. We will see lol. who knows might be someone out their who needs one of those motors. All I know is I have to be on the water this summer with my two kids, party time.

[johnmiffco]

good luck with the conversion
and a few good o/bs been popping up
on FB there is 3 300xs motors for 25k
so8,500 each is good deal
also saw pair 225 3.0s for 8k for pair
getting the transom rebuilt to hold the weight is the major part

[CaptainQ]

Thanks John, yes need the luck lol. Have not been on the water in my own boat for 10 years due to economy. I am a super Boat lover and I cant wait !!! I'm sure I will be posting more pics soon and needing more help lol. Maybe someone will have a bracket to hang the outboards, that is another big piece of the puzzle. Nothing like the sound of twin Bridge ports or 2.8 Race Mercs screaming down the lake, I could listen to that all day lol

[99fxst99]

I have done this same conversion on a Seebold 25. Used Bob’s Machine jacking plates rather than a bracket. Balance is better and less strain on the transom. Tied the jacking plate mounting bolts to the engine stringers with aluminum plate knees. Worked great. No movement or stress cracking in 6-7 seasons of use.

[CaptainQ]

How thick was the aluminum you used ?

[johnmiffco]

I sold my offshore vee last yr was a 27' Excalibur with triple 260+ offshores and was a blast ,,,fast and the harmony of 3 singing
on a deep vee hull u really want the motors inside the lifting strakes
so when get up to speed props stay gripping and not loose water pressure
as why suggested 2 single jack plates as most platforms motors split motors pretty wide

[CaptainQ]

Il bet that Excalibur sounded sick ! what was that boat pushing top speed no gas or people in it lol. A lot of motor for that size boat.

Oh yea i remember just need to see whats out there as far as jack plates go. I would even do two seperate ones that are fixed.

[johnmiffco]

didn't matter on load very much,,,
was a wave crusher hull 24deg bottom only 6' wide at transom
so was set up for offshore running hard in bays and the gulf
ballast tank in front to transfer fuel when needed for water conditions,,,ect
in 1' chop would only push it to 110 area as whole hull was lifting over 100
as had lifting strakes out the rear and low to bottom and would get transom loose from props surfacing
and want to prop walk,,,,,as props were only 1 1/2" apart so lots of tail lift for rough to keep bow stable in rough
as was set up more for rough running
but was fast to get from 0-110 when did throttle blips in right conditions

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[CaptainQ]

Wow that is a super sexy bad ass boat. That's living the dream lol and fast as hell ! I would be that guy at the dock waiting for you to start those motors lol

[99fxst99]

How thick was the aluminum you used ?
3/8 plate 5086 alloy

[CaptainQ]

Ok thanks, do you have any pics I can see ? just trying to get ideas .

[FUJIMO]

sounds expensive. and a lot of work. lots of glass & support system work required prior. lots of cosmetic work inside & out. big empty hole in the back when your done. have to figure out what to with that hole & then build it out. twin platform o/b bracket is thousands. get the right transom angle bracket, they are different. install TWIN everything. engines. props(and prop testing). throttles. shifts. gauges. fuel supplies. oil tanks. dual performance steering system. tie bar(s). throttle cables. shift cables. 2-cycle oil supply. trim tabs & trim tab controls & indicators. Just me, but that boat is a nice clean looking Switzer that I would simply degrease, paint, and install a BRAND NEW MerCruiser engine/drive PACKAGE into...and be done with it. SUPER EASY to install, can be done in a day, performs excellent, full factory warranty for years, turn key, go. and no loss come resale time, just an INCREASE in value.

[FUJIMO]

oh. and im an outboard guy.

[johnmiffco]

agree with above on time and money for a conversion done right
that 27 was a restoration of everything new but the hull and a super stout transom done
and lots of extras,,,,but what I do,,,,then run em till I meat my goals then build another,,,lol
also saw a low hr blue 500efi cheap and as stated before bravos are everywhere
but the twin o/bs are nice

[CaptainQ]

Thanks for that, i know it would be alot of work gages everthing. Who knows maybee start it this winter coming up. I agree with you 100%. It is just the boat I really want is an Outboard ripper . That other guy on here doing the checkmate looks like he has a big garage too, i defitly dont have that, work would all be done in the driveway lol. Who knows I probley would leave the big whole in the back I definitely like the big sun pad and that always comes in handy with the girls and my kids lol. That would be a sick boat with twins on the back. 2- 225s done right, right props , no people or gas probley put that boat into the 73-75 mph range that would be fun !

[FUJIMO]

couple year project in Wisconsin if you have everything and know what your doing...

[99fxst99]

Here are some pictures of the conversionI did from stern drive to outboard. I have more pictures but these address how I mounted the engines.
The rigging tubes running from the engines into the aft compartment passed through aluminum trim rings with slight clearance to allow them to move as the engines steered and trimmed. Not 100% watertight, but pretty weathertight and I never had any concerns with them.
With the engines turned straight ahead I could trim them out of the water.
If you have any questions I will be glad to share what I learned doing this conversion. It really was a fun project and I ended up with a great boat. Much better than the sterndrive. Went from 54-55mph with the sterndrive (330hp 454 Magnum) to a 74-75mph (stock 2.4L 200s with Bob's nosecones, 26 Choppers turning inboard).

[Instigator]

Bingo.

Tons of work, a bag of money and a pile of time.

Thats a small boat for twins too and would be a way better boat w/a single if you did do the conversion.

I looked at a similar Switzer yrs ago and would be careful checking existing structure before doing anything.

And yeah, I’m very lucky to have a big shop for mine.

I spent 2 yrs restoring a 24’ Sonic twin O/B in Fla, outside, under two Harbor Freight carport roofs zip tied together before I had the shop.

You have to want it ��


sounds expensive. and a lot of work. lots of glass & support system work required prior. lots of cosmetic work inside & out. big empty hole in the back when your done. have to figure out what to with that hole & then build it out. twin platform o/b bracket is thousands. get the right transom angle bracket, they are different. install TWIN everything. engines. props(and prop testing). throttles. shifts. gauges. fuel supplies. oil tanks. dual performance steering system. tie bar(s). throttle cables. shift cables. 2-cycle oil supply. trim tabs & trim tab controls & indicators. Just me, but that boat is a nice clean looking Switzer that I would simply degrease, paint, and install a BRAND NEW MerCruiser engine/drive PACKAGE into...and be done with it. SUPER EASY to install, can be done in a day, performs excellent, full factory warranty for years, turn key, go. and no loss come resale time, just an INCREASE in value.

[CaptainQ]

That is very impressive, that project you have going, nice job. I went though your post and seen that part were you cut the top of the exhaust holes up a bit. It looks like those supports went to those holes or by them. Could not figure out … What did the top of those supports attach too ? or did you just glass them to back of transom ?

[CaptainQ]

Nice looking boat, il bet that was a fun boat to own. Looks like you did a lot of work to that transom , how long did all that take you and how much money just into completed transom thanks

[SUNKIST]

i have these 200 merc outboard mtg brackets for sale. they are made to fit std. 3 liter wingplates. i made these out of 316 stainless to save a ton of money. 450 for the pair shipped. just the brackets. no wingplates or tie bar.436430 436431 436432

edit..have a tie bar also.

[CaptainQ]

i have these 200 merc outboard mtg brackets for sale. they are made to fit std. 3 liter wingplates. i made these out of 316 stainless to save a ton of money. 450 for the pair shipped. just the brackets. no wingplates or tie bar.436430 436431 436432

edit..have a tie bar also.
Wow nice job, they look good. I will keep those in mind. First I need to sell currant motor. What size is that boat you have those twin 200s on?

[99fxst99]

Nice looking boat, il bet that was a fun boat to own. Looks like you did a lot of work to that transom , how long did all that take you and how much money just into completed transom thanks
Start to finish November to May. Except for the glass and paint work I did the entire job. Only thing I had help with was bleeding the steering. Had about 600-800 in the transom work.