I/O to outboard conversion

[danthern]

Hey Guys....I have a 1977 24ft Wellcraft Airslot that I want to restore. The engine and outdrive (OMC) and gone and I'd like to go back with outboard power. Is it feasible to assume that this could be accomplished by glassing in the outdrive hole and refashioning the transom to accept the outboard motor? Thought I'd use the former motor location as a fishbox or something....Would y'all advise this and if so, what size motor would you go with? Was powwered w/a 235hp Ford 351.
Thanks for your thoughts

 

[Solittle]

Re: I/O to outboard conversion

A number of posts have been written on this. Try the search function.

One beware I remember is to bake sure the weight distribution is pretty much the same or the hull will be out of balence fore and aft from the way it was designed as the I/O is usually much heavier than an OB.

I would think you would need a pair of V6s to adequately power that hull.

 

[danthern]

Re: I/O to outboard conversion

Thanks for the info. I tried to search this, but since the site has changed it is a chore. Came up w/ nothing which I know can't be true. I'll try again..Thanks alot!!

 

[Bob_VT]

Re: I/O to outboard conversion

There are companies that make brackets specific for that purpose. It usually sets the outboard back almost 2 feet. The lost weight of the iron V-8 and the outdrive is significant and the cost of a good single outboard or twin outboards will be huge!

I am not trying to discourage it (you will gain alot of room in your boat) but for the money involved you could repower and install a new outdrive. Do not anticipate any fuel savings with the outboard.... even if a 4 stroke.

 

[danthern]

Re: I/O to outboard conversion

Thats the kind of thing I need to hear. maybe going back I/O is the thing to do. Thanks

 

[Bondo]

Re: I/O to outboard conversion

Ayuh,...........

I know several people who have Tried it,........

None of them considered it a Success,.......
The boats were either Junked or Sold within the year......

 

[tashasdaddy]

Re: I/O to outboard conversion

there is more to it than it looks. the i/o is mainly supported by the engine mount one the stringers. the transom would really have to be beefed up to support the mounting bracket and the engines hanging 2 ' off the stearn, changing the center of gravity of the complete boat. the cost of the refit of the boat and engines is probably be more then a refit with the i/o. if you really like the boat and it does what you want , i'd go for replacing the i/o. and i'm and OB person.

 

[danthern]

Re: I/O to outboard conversion

Thanks for the input. I/O repower it is. Was set up for a stringer. Am I forced to go back with that?

 

[Tacklewasher]

Re: I/O to outboard conversion

Hmmm.

Guess I'm the weird one.

Did just this to an 18 foot Starcraft Holiday. It worked becasue the existing transom was substantial to start with and I further strengthened it. I doubt I could ever sell the boat with these modifications, but it is working well for me.

Under no circumstances go back to a Stringer. Junk the boat first (IMHO). Who wants a motor that can't be trimmed up when coming into shore? And finding parts for those things can be a pain in the butt.

I just don't know how you could switch outdrives with that big hole in the back of the boat.

 

[Bondo]

Re: I/O to outboard conversion

Whichever way you were to go,...... You've Got to Plug the Hole...........

A few small pieces of Plywood,+ some Epoxy,...........Done Deal........

The Absolute Best way to do a Refit like this,...... Short of Brand New components,......
Is to shop around,+ find a Good Running boat, that has all the components that you want in Your Boat.......

Then Buy it,+ Junk it,....... A Donor Boat.......

That way you get all the Little Pieces,.......
The 1s that end up Co$ting a $mall Fortune.......
And,..... There are Lots of boats around for $3 or 4,000.00,...... That's less than 1/2 the price of New,.......
And, you get all the Extras......

Finding the Right Donor is the Key,........

 

[Tacklewasher]

Re: I/O to outboard conversion

Whichever way you were to go,...... You've Got to Plug the Hole...........

A few small pieces of Plywood,+ some Epoxy,...........Done Deal........

Just be aware that the whole is friggin huge with the stringer drive. It's more than a little plywood. Mine was an inch thick and about 2 feet by 3 feet. That's why plug for my hole is sandwiched between even more plywood.

 

[Bondo]

Re: I/O to outboard conversion

Whichever way you were to go,...... You've Got to Plug the Hole...........

A few small pieces of Plywood,+ some Epoxy,...........Done Deal........

Just be aware that the whole is friggin huge with the stringer drive. It's more than a little plywood. Mine was an inch thick and about 2 feet by 3 feet. That's why plug for my hole is sandwiched between even more plywood.

Ayuh,......... I've Done 4 of them,........

The Actual Hole left by a Stringer Drive is about 18" around,............
And,..... If you're installing a Mercruiser,..... It Better be 2" Thick,..... The Combined Total Thickness........

The last 1 was 2 layers of 3/4 Plywood,.... The Outer "Skin" from the Donor Boat,+ the rest was the Epoxy,+ Glass........

 

[danthern]

Re: I/O to outboard conversion

Having said all that, would y'all recommend a Mercruiser or am I safe to go w/ a Cobra?

 

[Mark42]

Re: I/O to outboard conversion

Although I have never done this conversion, I have kicked the idea around a bit while looking for "doner" hulls for a project boat.

A few interesting points:

- A new 250 hp Evinrude v6 weighs 516lbs dry.
- A new Mercruiser Sterndrive 220 hp w/bravo drive is 912 lbs.

That is a difference (savings!) of about 400lbs. Or roughly the weight of two fishing buddies.

The difference in 400 lbs in relation to the boats "balance" is partially addressed by having the O/B mounted further to the rear.

If the weight difference is really that big an issue, then relocate whatever equipment possable to the rear. The space where the motor was located can be re-used for additional fuel tanks, and/or bait wells, and/or equipment storage. If the existing fuel is relocated to the rear, then the weight re-distribution may be all it takes to get a good balance back. Also, a 1977 boat could probably use a fuel tank upgrade/replacement by now anyway.

Most folks are conserned about the strength of the transom. I don't see that as being as big an issue and is addressed by building in whatever support is needed to hang 512lbs of outboard on the back. Plus, the added weight of a new transom that will support the motor will go towards balancing the weight difference.

Remember, this is a 24ft boat. How much is the boat affected by having 400lbs of passengers and gear up front as opposed to the rear?

Just my $0.02

 

[tashasdaddy]

Re: I/O to outboard conversion

go with what is currently able to be serviced. some omc, cobra parts and service is getting rare. basically mercruiser and volvo.

 

[Bondo]

Re: I/O to outboard conversion

Having said all that, would y'all recommend a Mercruiser or am I safe to go w/ a Cobra?

OMC is Gone,....................

Would you buy a Chevy or a Rambler...............

I see the Only Choices are Mercruiser, the Most Popular,+ Easiest to Find parts for,......
Or,... Volvo........

 

[JasonJ]

Re: I/O to outboard conversion

You don't have to use a bracket either. You can rebuild the transom to the desired strength, and also build in some "knees", or braces from the transom the the stringers that supported the original drivetrain. This way it is bringing the weight closer to the boat, helping to maintain balance. One other thing to consider, weight placement in regards to balance is not an absolute. There are more than a few boat makers that have offered the same hull in I/O and outboard, without detriment to handling. The problem of weight distribution is fixed by moving the fuel tank forward towards the bow, under the floor, moving batteries, livewells if so equipped.

If it were me doing your project, I would not go back to I/O. You will want to go with a complete Mercruiser drivetrain, which people do not just give away. You will have to do transom modification as well as stringer modification to get it right. When all is said and done you will still have an I/O.

The question you have to ask is what is the intended use of the boat? Fishing, cruising? The next question you have to ask is are you so in love with this boat that you can't just sell it and find a boat that better suits your needs without all the hassle? You would save a bunch of money if you did just get another boat.

Now, if it must be this boat, then I will recommend an outboard conversion, without bracket, followed by a Mercruiser conversion. Costwise, its a wash, between a good, complete Mercruiser drivetrain and a good used outboard of significant power output. Good luck either way...