from I/O to outboard

[Part-time]

I have a Sea Sprite deck boat that had a 140hp 3.0 I-4 with a POS OMC that wouldn't stay together.
It took me about 2 hrs to take it all out and I actualy found someone that wanted it and traded me a mid 80's 25hp merc xd for it.
Perfect motor for my little 14' steel hull.
Now, getting back to the deck boat...

BTW, the boat is a 19 1/2 footer.
Just because I know everybody likes pictures so much!!!

 

[Woodonglass]

Re: from I/O to outboard

Installing a bracket (POD) changes the dynamics of the boat. The center of effort, line of thrust and center of floatation change among others. It works better on some boats than others. Porpoising is the usual side effect of extending the motor aft. Trim tabs help. It is a lot of work and expense. A general rule of thumb from what I have been able to learn is about 1" of rise on the motor for every 12" of Set Back. You should be able to determine that by tilting the motor when it is on a stand. Your POD design will need to accomodate the cabling, cowling etc. IMHO I would much rather see you modify the existing transom and hang the motor on it. mo

 

[Pmccraney]

Re: from I/O to outboard

Many on here (including me) would encourage you to ditch the OMC stringer. However, I also sense that many of the experienced guys (including WOG ^^^), which to be clear, I am not, may simply encourage you to convert to a merc i/o set-up as opposed to converting to an o/b set-up (and that's only if you are dead set on keeping the boat and up for a good project). I think a common observation from these experienced guys is that a lot of conversions fail and most people are not happy with the boat performance afterward. Of course, I can't speak directly to this, and I am just reporting what I have read after lurking around this forum a good bit for the past 6-8 months.

I think there are a couple of open threads on here that you may want to look at: Weldzilla has done what appears to be a successful conversion, but I think he had a lot of experience and took a bunch of detailed measurements to make it work. Also, "Captain kickback" is doing an i/o to o/b conversion as well. i would read their threads and maybe reach out to them if you have some questions.

Whatever you decide, good luck!!

rpm

 

[Part-time]

Re: from I/O to outboard

It was my original idea to modify the transom to accept an outboard... but it just seems much simpler to build a bracket and then brace from the inside to the stringers where the engine used to mount.
It also just gives me that much extra space inside the boat.
I should have weighed the OMC outdrive and the 3.0 before getting rid of them but I'm guessing the 150 Black Max probably only weighs about half as much???

 

[Woodonglass]

Re: from I/O to outboard

I understand the space issue but you really need to understand the dynamics that this modification places on the boat. It's a lot more complicated than just plugging the hole and hanging a POD on the back.

 

[oops!]

Re: from I/O to outboard

most of the i/o to ob conversions dont really work to well....or better said, the owners dont like the boat a s much. as the dynamics change.

i have heard of a few that did work, buy over all the results are less than expected.
a ob conversion is a standard idea the omc owners try to go to, in order to save the hull.

a merc swap has a far higher success rate than a conversion.

but weldzilla has done a great job on his and is very pleased with the results. search is link.....

 

[Part-time]

Re: from I/O to outboard

After reading Weldzilla's thread I'm definately going that way!
I think that ditching that extra weight can compensate for having the motor that far back.
The other reason for going O/B is I already have the motor, the merc outdrive I don't.
And as for the handling or anything else... Anything is going to be an improvement over the OMC!
It never worked long enough for me to really know how the boat could go :facepalm:

 

[Part-time]

Re: from I/O to outboard

Another option just poped up!
I picking up a complete jet drive unit this morning...
Maybe a 454 BBC powered jet deck boat?

 

[boatnut74]

Re: from I/O to outboard

A 454 jet drive would be way to much power for that boat. You would be adding 200+ horsepower over fatory. It would be unsafe to do it that way. That's just MHO.

 

[Part-time]

Re: from I/O to outboard

I was only kidding about a 454 but I might go with a TBI 305 or 350 cid.
I want something that will let me cruise 30-35knots and pull tubes and skiers without having to use all that she's got...
Just because it's there doesn't mean I have to use it.
I'm thinking a SB V-8 with a jet drive must be pretty close in weight to the stock OMC and 3.0 I-4 that used to fill that hole?
Any imput and comments is apreciated, doesn't mean I'll listen to 'em all but I definatly give 'em all some thought.

 

[zopperman]

Re: from I/O to outboard

i/o's don't have any HP limit for a reason

 

[Part-time]

Re: from I/O to outboard

Ok, the idea of the OB was droped in favor of the jet drive.

The OMC is long gone
A SB 350 (260 mercruiser) is going to fill this space

Now I have to do some more repairs to the hull.
As I was bringing the boat up river to the boat ramp I have to go under a bridge and as I was lined up to go through the hole (there's 2 spots for boats to go through under this bridge, both one way trafic and about 12' wide)... I spot a padle boat coming down river on my side. I had no more reverse so all I could do to stop was turn the wheel.


I'm not getting into splitting the deck, I hope... Are these repairs posible just from the outside?

 

[Decker83]

Re: from I/O to outboard

Love the Deck Boat.
Good luck with your project.
I'll be watching this thread for information.

 

[Part-time]

Re: from I/O to outboard

Here's the donor for the sbc 350

the outdrive was seized but after I pulled it off the motor started and ran like a dream!
I got this boat in trade for the 25 merc xd that I had got in trade for the original OMC sterndrive from the deck boat.

 

[Woodonglass]

Re: from I/O to outboard

IMHO the damage in the pics looks to be above the water line. If so then it can be done from the outside only. It prolly should be done from both sides but... You can do it from the outside only. R U absolutely certain that you do not have waterlogged foam below deck??? Some of those deck boats were completely filled with foam and if it is waterlogged it could add 1,000lbs+ to the weight of your boat.

 

[Decker83]

Re: from I/O to outboard

Take a look at all the foam in my Deck Boat. It's a 1983 and it was full of foam.
The foam had water in it all over the boat. Some really dry and some soaking wet.

 

[Part-time]

Re: from I/O to outboard

Well, I wanted to strip the century but mother nature had other plans for the weekend.
She made me shovel some then turned on the deep freeze.
Ended up being -29*C (-20*F) not counting a 15-20 mph north wind.
No working outside today.
I got tired of having that boat in the midle of my driveway and the trailler wasn't mine and I wanted to return it sooooo.
http://youtu.be/nU3THymwUeY

I guess I might be a bit of a redneck

 

[Part-time]

Re: from I/O to outboard

I thought the 'D' ring on the left side had just broke off when you see the swimstep fly but it tuns out the transom is so week it just pulled out through the plywood and all... even the metal backing plate that was on the inside

 

[WeldZilla]

Re: from I/O to outboard

I certainly had success with my conversion. Make no mistake about it I believe still that most have not. Guys who have done it say it went well but their lack of pics makes me wonder. Usually when a guy (ok check that) a person has great suuccess on something and they belong to a forum about it you see a ton of pics and you can tell by the wording in their posts they are excited by what they accomplished. Most of the time you see an outboard that is half under water as they come up to plane and then you don't really see any planing pics. These are things that make me go Hmmmm?

You could easily convert that to an outboard. Most transom brackets you buy setback about 28 to 31 inches. I'm telling you straight up you must get a motor with a 25inch leg. I went with 29inches on my bracket as it allows me the room behind the transom to fully tilt my motor and it gave me a nice platform. My Suzuki140 was also light enough that the extra leverage did not hut me. I know your engine out drive combo you have now weighs in at about 650 to 695. Your brack will weigh about 90 pounds including all hardware. Keep your motor at under 500lbs. less is better. With a 29 inch long bracket I mounted the bracket so the top of the engine mount was 28 inches not 25inches. That far behind the boat your engine is riding in the swell that is created as the water compressed under your boat rises up as it comes out from under your boat. By having the top of your mount at 28 inches that will accomdate the swell so your engine is not drowning. You can also raise it a hole or 2 if necessary but 28 should be about nuts on. Now the next question is your transom in good shape?
Good luck whichever way you go

WZ

 

[Alwhite00]

Re: from I/O to outboard

I thought the 'D' ring on the left side had just broke off when you see the swimstep fly but it tuns out the transom is so week it just pulled out through the plywood and all... even the metal backing plate that was on the inside

Maybe you could have been going a little faster and they both would have pulled through. I think if you pulled on it gradually it probably would have held. Even if it was not rotten it might not have held up to that.

Looks like an ambitious project, Keep the pics comming.


LK