I/O to Outboard Conversion

[joezek]

I'm about to attempt a fun little project over the next year, hopefully be done by next summer. Looking at a 1995 Riviera 21 ft bowrider that's missing the engine and outdrive. The hull's in solid shape, needs cushions replaced and new covering on the instrument panels. The thing I love the most about this boat is the huge amount of rear interior space, and now with the engine removed it's got another 4 more feet of interior. I don't go offshore, or in rough water. I go from the boat ramp to the sand bar every weekend and party with friends. We currently have a 16 ft grumman with no room at all. So for us this is everything my wife and I want so we can bring friends and our dogs.

The plan is to reinforce the transom and install a 30" bracket, and an outboard. I've looked at plenty of center consoles, and bowriders, and there's just nothing with even remotely close to this much free room as when you do the I/O to Outboard conversion. Most of our friends have 26-30 foot center consoles made for deep sea fishing, nice T-Tops etc, and they just simply have no room inside the boat. I guess the front of the boat has some room. If two people try to walk around the console they're pushing each other out of the way, I don't want that, I want big open area. We don't fish, we just cruise in the Intracoastal waterway.

I'm looking for a source of information about this Riviera boat. I can't seem to find any online sources listing the specs as in weight, width, original horsepower setup, etc. I don't know if it's the same company that makes the motor yachts. It' seems to be a fairly heavy hull, I had to jack it off the ground today since it's laying in someone's back yard in the weeds. I'm thinking around 2,800 lbs?

I'm guessing that when the time comes I'll be shopping for an engine in the 175-200 hp range?

Anyone who's done a conversion please chime in. I know it's becoming a pretty popular thing to do nowadays- instead of buying a much bigger boat.

 

[jigngrub]

Re: I/O to Outboard Conversion

If it's laying on the ground in the weeds I'm gonna go out on a limb and say that the boat probably has waterlogged foam and probably some internal wood rot that'll put you into full restoration mode should you decide to go ahead with your plans.

Fiberglass boats that have sat out in the elements for any length of time are nasty nasty nasty!

 

[mark1961]

Re: I/O to Outboard Conversion

I dont know of any other "Riviera's" except the ones built in Queensland Australia which are normally much larger vessels.....if this is what you have (and im not sure that it is) you could try contacting the company for information......or post up some pics, somebody may know the breed.

http://www.riviera.com.au/about/aboutus.cfm

 

[joezek]

Re: I/O to Outboard Conversion

As for rotting on the ground- He just recently had listed the boat/trailer combo for sale within a month. Last week he sold the trailer and just left the boat sitting on the ground instead of nicely putting it on blocks. I'm pretty sure it hasn't been sitting on the ground for a long time, and when I jacked the bow up real high there was only a small puddle that came out of the rear drain. I did walk around and push on the hull and sides to feel and look for soft spots. The only soft spot was where the seller pointed out, barely noticeable soft spot under the driver seat foot area. It's a wooden floor with carpet over it so..... I was expecting worse. Although my 1983 Grumman still has it's original wood floor and no soft spots. I know it's original, my inlaws bought it brand new 28 years ago.

 

[relocyo]

Re: I/O to Outboard Conversion

Ouch, that soft spot needs inspecting, dont be surprised if Jigngrub is right and it needs a floor, stringers and be sure to check that transom as your plans rely heavily on its condition. Good luck, post back...

 

[joezek]

Re: I/O to Outboard Conversion

Well I got the boat, and see that the title says the manufacturer name is Rivertra. I don't know if this is a typo or if it's really a manufacturer. The side of the boat it says Corona, which is the model. There's so many boat manufacturers it's hard to find info on them, especially when they go out of business all the time.

The boat's 21 foot with an 8 foot beam, feels very solid.

 

[joezek]

Re: I/O to Outboard Conversion

I finally figured out exactly who manufactured my boat and have some better specs on it after lots of help from Google. It's a Corona by Seahart Manufacturing Co. The beam is 8 ft, 3,340 lbs dry, 21.17 ft long.

The title is not very helpful. The vin number on the title exactly matches the vin number that's permanently etched into the boat. However there's some blank information blocks in my title. The "Make" and "model" blocks are empty. Then the block that says "odometer status or Vessel Manufacturer or OH use" block says RIVERTRA. As a result the seller mistakenly thought it was a Riviera boat with a misprinted title. The title is also missing the "color" block as well.

I'd like to know if it's possible to correct the information blocks when I apply for my title when registering the boat. To confirm the manufacturer, I looked at the metal plate in the front of the boat which says the maximum number of passengers, max HP, and max weight to be loaded. The bottom of this metal plate says Seahart Manufacturing AR. (my max load is 1,200 lbs).

Has anyone edited the information in their title? Also after I convert from I/O to outboard is it possible to edit the title to show it's an outboard boat? Currently it says IN/OUT.

 

[zopperman]

Re: I/O to Outboard Conversion

I'd take your title questions to your state's dmv... Where are you located? As for what Jiggy said.... take core samples. The floor probably has a layer of fiberglass over it unless it's been replaced... poorly. You take a croe sample by drilling (with 3/8" bit or so) into the deck, stringers, and transom in various locations and assessing the quality of the shavings. Wet and dark = rot and must go. Dry and tan and light = . Then fill the holes with 3m 5200. I would seriously check these things before continuing iwth your project Also, you'll be fabricating your own transom so I guess it insn't a huge deal even if it is rotted... but that likely means the floor and stringers aren't in good shape.

 

[joezek]

Re: I/O to Outboard Conversion

I'd take your title questions to your state's dmv... Where are you located? As for what Jiggy said.... take core samples. The floor probably has a layer of fiberglass over it unless it's been replaced... poorly. You take a croe sample by drilling (with 3/8" bit or so) into the deck, stringers, and transom in various locations and assessing the quality of the shavings. Wet and dark = rot and must go. Dry and tan and light = . Then fill the holes with 3m 5200. I would seriously check these things before continuing iwth your project Also, you'll be fabricating your own transom so I guess it insn't a huge deal even if it is rotted... but that likely means the floor and stringers aren't in good shape.

Located in Florida. The floor feels very solid everywhere, I'm not worried about it at all. The boat's solid throughout. The transom appears to have been built pretty strongly as well, and I'm working on some stainless steel supports that'll connect the transom to the original engine mounting points on the floor. Also plan on putting in a big stainless steel plate on the inside of the transom that the outboard bracket will attach to. The plate will distribute the load over a much bigger area. I've got a friend who welds for a local boat company, who's going to help make the supports. The planning is going well, hopefully things will flow pretty smoothly over the next year.

 

[zopperman]

Re: I/O to Outboard Conversion

Well, I don't know anything about florida title laws... I'm sure it's similar to NJ where you can request a new title and make changes ETC... While I don't mean to belabor the point, that soft spot is an issue. See the link in my sig... That started with a soft spot in the deck.... While the rest of the deck felt solid and I thought I could cut that out, I soon learned that a soft spot is generally indicative of larger issues. Also, an I/O transom isn't build like an OB transom... the weight distribution is different... Also... the boat isn't built for an OB. It is designed to have a 1000 pound inboard in teh engine compartment.. the OB is probably closer to 400. My guess is you would need twins to: 1. power the boat adequately, 2. balance out the weight issue and you would probably have to move them back. A 200 HP probably won't move that boat too quick.

I'll admit.. this is a fascinating project and I wish you the best of luck and I'll be following it closely, but I have yet to hear a successful one here on iboats...

PS -- on the transom metal etc... metal is bandaid over rotten wood... make sure you use fresh wood and treat is properly and glass it well ETC. You say appears a lot... You don't know till you drill core samples.. Also, look into a product called sea cast, you need an inner and outer transom wall to pour it, but it won't rot.

here's a quote on this from another similar post...

Thoroughly research this before spending a bunch of bucks. There have been several posts here on this where the results were not to the users liking. Beware of the changes in weight and center of gravity. Most hulls are designed with the type of power as an important consideration in the design. I remember complaints about how the boat sat in the water and handling/performance.

The transom has to be beefed up besides covering the hole. An I/O's weight is supported by the hull stringers whereas the transom has to carry the weight of the outboard. This is a major deal. In addition, the current hull was designed with an I/o. Simply bolting an outboard to the rear may not give you the satisfaction and performance you desire.

 

[Lou C]

Re: I/O to Outboard Conversion

This is something that takes a lot of thought and planning, you have to keep in mind that an outboard puts very different stresses on the transom than an I/O. With the I/O, the front of the engine rests on the engine stringers, the rear is supported by the transom plate on the transom. The drive does put thrust forces against the transom. An outboard transom is under much more stress, the entire weight if the engine, is cantilevered on the transom, you can see this when watching an outboard boat with the engine all the way up being trailered. It has to be stronger and supported differently (supports going from the inside of the transom to the stringers).

Personally if I wanted an OB boat I'd sell mine and get one built that way from the get go. Yes some have made the conversion but cheap it ain't and you are now the boat designer/engineer. Will it be balanced right and run right after all that work?
I/Os are not that bad if you don't keep em in the water. To re-fit it with late model I/O components would be cheaper, easier, and there would be no issues of balance and handling. Yes they take up room, but build it with an engine dog house and a jump seat on either side and that gives the most room inside.....

 

[joezek]

Re: I/O to Outboard Conversion

Luckily the transom is 1 1/2" thick, it's a good start. Today I spoke to someone who did this recently and they told me that most I/O transoms are only 1" thick, and most OB transoms are 1 1/2" thick.

I live in a town that calls itself the "Sailfish Capital of the World", and it's got about 20 different tournament boat and yacht manufacturers. I'm surrounded by marinas, boat supply stores, and best of all lots of extremely knowledgable guys who build and modify boats on a daily basis- for a living. A customer of mine who's airplane I work on, is one of the best in town well known for completely chopping and modifying old boats and turning them into top dollar off shore fishing competition boats.

I'm not just blindly throwing parts together and expecting this to magically work, I'm thoroughly thinking out each step and getting excellent advice from every source I can. I'm also an aircraft mechanic for the last 16 years with a 4 year college degree at Embry Riddle University. I took 2 years of engineering and drafting classes and have a thorough understanding of the basic idea behind supporting an engine. I'm designing a basic support system for the engine/bracket that's going to mostly utilize the original engine supports and also connect the upper part of the transom which wasn't previously supported very well.

I'm using standard aircraft weight & balance procedures to come up with the approximate amount of weight the transom is gonna be dealing with, based on the weight of the engine X the length of the arm (distance away from the transom) etc. That's also helping me try to figure out the CG of the boat before and after. Previously the engine/outdrive was probably around 800 lbs mostly centered around 20" forward of the transom. Now I'll have probably 400 lbs centered about 3 ft aft of the transom. So now instead of 16,000 in/lbs pushing down on the boat just forward of the transom, I'll have 14,400 in/lbs lifting up on the boat/pushing down at the imaginary point 3 feet aft of the transom (3 foot bracket). It's probably gonna promote porpoising or making the rear of the boat want to sink, and it's just another part of the experiment and learning process in this conversion.

PS I've googled a few minutes and found plenty of people who've done this mod. A lot of people consider this a really nice upgrade since you're now dealing with an OB, less noice, better performance etc. Please only post here with positive help or ideas, but don't tell me I need to give up and by a different boat.

 

[produceguy]

Re: I/O to Outboard Conversion

I think most I/O are 2" thick. Thats wood and glass.

Sounds to me you have a great handle on it and you seem to be very intelligent so I'm sure it will turn out good. Good luck.

 

[zopperman]

Re: I/O to Outboard Conversion

i don't think anyone has said to give up.. we just want you to be aware of the risks and potential problems that aren't so obvious, even to an educated person. Personally.. I'd just hate to see you do such a project then find some floor and stringer rot and have a whole other emss on your hands.

Moving on, I believe that there's a company in FL that actually manufactures brackets for this purpose that are from $600-900.. i remember reading that here on iboats in a similar thread...

 

[joezek]

Re: I/O to Outboard Conversion

When I got this boat I had a specific timeline and amount of work planned in the back of my mind. I gave myself until next summer to get it ready for my wife and I and our dogs (and friends) to be able to enjoy it in a few runs up the river and weekend trips to the sandbar. I knew the labor involved, and was looking forward to a challenge. I paid a measley $100 for it and I already know the saying that the most expensive boat a person can get is free....So at least it wasn't free.

This boat is a hobby, it gets me out of my boring house every night. Right now it's only costing me a few dollars on glass, wood, and resin- bottom line. When I'm satisfied with a bulletproof transom I'll buy a bracket and save up for a used outboard. I have the ability to figure out how to engineer it to be stronger than the Brooklyn bridge if I want to waste that much time on it. If it's got too much weight aft of the the transom then I'll move the fuel tank forward and install trim tabs, I don't know- it's just a hobby, I'll figure it out.

Today I cut off the glass around the hole in the transom to see how bad the transom "really" was because it was delaminated at the removed outdrive hole, turns out I have to replace the 2" thick wood/glass transom. My thought upon seeing this- "So what". So tomorrow I get some wood, cut it to fit, and borrow a sawzall, and get the damn transom done. Apparently the old outdrive wasn't sealed up good and soaked up a **** load of water into the transom which ruined it. That explains why it felt like a 5,000 lb boat when I towed it home.

I didn't start this project with the thought of selling it to someone else. I live in a town that sells high end boats at a fraction of the cost at the end of every summer because there's way too many people who can't afford their own gas. I started this project because I wanted something to do. My point is, this boat aint going anywhere until I'm finished putting my outboard on it, and it's going to be built like a Sh#t brickhouse.

I've got 4 knee braces ready to go, a couple spars connecting the stringers, and some braces connecting the top of the transom to the sides of the hull. I have a big bracket connecting the original forward engine mounts simulating the original engine block too, which reinforces the left/right rear hull. I'm adding a ton of reinforcement to the entire floor area in all directions around each knee brace. The knee braces are at two different angles to spread the load, and to prevent oscillation frequencies caused by running at one continous RPM. Honestly the only problem I'm worried about is low speeds because the rear of the boat may sit low like the race boats we see around here.

Just in case I don't have a clue what I'm doing, I'll bring a life jacket for my wife so she can tell you guys how wrong I was.

 

[zopperman]

Re: I/O to Outboard Conversion

Hang on to that sawzall. It will come in handy

If the boat felt heavy, check the foam too.. that absorbs water like a sponge. and watch what you say about free boats!!!! shhh....

And can we see some pics!!

 

[joezek]

Re: I/O to Outboard Conversion

http://s251.photobucket.com/albums/gg306/gto7878/The%20Ark/

This is the link to some pictures from last week. I got a lot more glass work done after these pictures. Filling in minor gaps and glassing over them. The outside needs to be finished up also. I planned on finishing the inside part using black gel coat to neaten it all up. I also gotta make a few drain holes in between the knee braces.

Overall I'm very happy with the design and outcome of it. It's built really strong and not too heavy. I'm using Biaxial glass and Polyester resin over most of it, aside from some chop glass to fill in the open areas where strength isn't the main focus. Those (4) knee braces basically make the transom and floor all one solid piece. Then that giant 2 X 12 that's connecting the top of the transom to both sidewall stringers of the boat puts it over the top as far as extra strength.

Now I gotta start looking for a 3 foot bracket, outboard engine, and continue making some floor repairs- then interior too.....It's true, free boats are the most expensive thing you'll ever have.

 

[boatnut74]

Re: I/O to Outboard Conversion

Good to see you back joezek. Looks good so far. Have you decided how big of an outboard you want to run. I would still be concerned about that soft spot in the deck and the potential for waterlogged foam but that's just my .02
Also it's hard to tell from your pics but is there transom wood across the whole back or just that small piece in the center? Bolting on a bracket and heavy motor would put alot of stress on the back of the boat. I would assume it would be best to have a bigger wood transom in there.