I have a 21' Grady with an OMC I/O. Has anyone out there ever converted from this to an Outboard?
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Converting I/O to an Outboard
- Thread starter Mobjack Bay
- Start date
gerrys
Well-Known Member
I did the conversion on an older 22 foot Invader that I owned years ago.
Here's the good and the bad:
We removed the I/O (350), glassed up and reinforced the transom, then added a bracket and a new Yammi 225. I used the space gained under the deck for an additional fuel tank. The boat ran like a scalded dog - I mean the performance was absolutely great!
After about a month while returning from about 50 miles offshore, I noticed the floor flexing with every pound of a wave - not good. I pulled the decking to find that the stringers were broken, primarily due to age and the huge cantilever we hung off the back of the boat. Lucily I bought the new boat from the dealer who sold me the new Yammi and he credited me fully for the return motor but not for the glass work or the bracket.
I think you can be successful but you have to consider the overall impact of putting all that weight and torque way out there on the back of the boat. Get a good structural inspection and don't spare the reinforcement.
Here's the good and the bad:
We removed the I/O (350), glassed up and reinforced the transom, then added a bracket and a new Yammi 225. I used the space gained under the deck for an additional fuel tank. The boat ran like a scalded dog - I mean the performance was absolutely great!
After about a month while returning from about 50 miles offshore, I noticed the floor flexing with every pound of a wave - not good. I pulled the decking to find that the stringers were broken, primarily due to age and the huge cantilever we hung off the back of the boat. Lucily I bought the new boat from the dealer who sold me the new Yammi and he credited me fully for the return motor but not for the glass work or the bracket.
I think you can be successful but you have to consider the overall impact of putting all that weight and torque way out there on the back of the boat. Get a good structural inspection and don't spare the reinforcement.
Amigo
Well-Known Member
I converted an 18ft. aluminum boat from an I/O to an outboard.
It has been 6 or 7 years now and it has been a suscessful conversion. I agree with Gerry. Check the stringers for rot.
I replaced the transom plywood (rot) with three pieces of 3/4" plywood epoxied together for a thickness of 2-1/4 plus a bit for the epoxy in the sandwhich. (Easier to do with an aluminum boat.)
I also had stainless "Knee braces" made for the boat. The braces were through bolted to the inside of the transom plywood and then to the stringers in the area where the inboard engine was mounted. That stiffened everthing up. The bracket is mounted to the transom with 6 - 1/2" stainless bolts with channel used as back up plates.
The engine and outdrive weighed 600 lbs and the outboad and bracket weighed 400 lbs. She balanced out well and sits in the water just fine.
I have trailered this boat many times into N. Ontario for a 1,200 mile round trip. In the summer of 2007 I put 1,400 water miles on the boat and 1,200 trailer miles chasing walleye/pike in Ontario and salmon on Lake Michigan.
I happy to report that the engine is still firmly attached to the boat.
It has been 6 or 7 years now and it has been a suscessful conversion. I agree with Gerry. Check the stringers for rot.
I replaced the transom plywood (rot) with three pieces of 3/4" plywood epoxied together for a thickness of 2-1/4 plus a bit for the epoxy in the sandwhich. (Easier to do with an aluminum boat.)
I also had stainless "Knee braces" made for the boat. The braces were through bolted to the inside of the transom plywood and then to the stringers in the area where the inboard engine was mounted. That stiffened everthing up. The bracket is mounted to the transom with 6 - 1/2" stainless bolts with channel used as back up plates.
The engine and outdrive weighed 600 lbs and the outboad and bracket weighed 400 lbs. She balanced out well and sits in the water just fine.
I have trailered this boat many times into N. Ontario for a 1,200 mile round trip. In the summer of 2007 I put 1,400 water miles on the boat and 1,200 trailer miles chasing walleye/pike in Ontario and salmon on Lake Michigan.
I happy to report that the engine is still firmly attached to the boat.
gradyfish22
GreatGrady Captain
You can do it, but like mentioned above, you will need to consider the structural intergrity of the boat. Best bet is to remove the stringers aft of the last bulkhead and then replace them with new beefier ones that can withstand the load of the new engine placement, whather it be a bracket or notched transom. The transom should be reinforced for sure, and reglassed over on both sides to insure safety and strength. A good yard should be able to do this, but you might want to consult someone with an engineering background or a structural consultant to review what you might need as far as layup to be strong enough. Likely it will be a cored foam stringer and glassed with anywhere from 4-6 layers of glass, likely both bi and tri axial glass, there are many ways of doing it and every yard or consultant will give you a slight variation. There is not right or wrong way, they just might require more layers, cost different, or weight more or less. I think going to an outboard is a smart move if the boat is in decent shape and will not need major work, and that you plan to keep it for a while. The new added space can be used for tons of things...an indeck fish box, or an aux fuel tank, even a big livewell or dry storage boxes. You have tons of options for that space, plus more fishing room. You could add jump seats along the transom if you wish, or cooler and fish boxes, or leave it flush and just have more open space.
If I were doing it, I would add a bracket with floatation to handle a four stroke, and use the engine compartment space for 2 things....aux fuel tank, and a big fish well or livewell. You may also need to put the batteries down there on a shelf out of the bilge floor so remember you need access to them if they are to go there. You can get very creative with this project if this boat suits your needs well.
If I were doing it, I would add a bracket with floatation to handle a four stroke, and use the engine compartment space for 2 things....aux fuel tank, and a big fish well or livewell. You may also need to put the batteries down there on a shelf out of the bilge floor so remember you need access to them if they are to go there. You can get very creative with this project if this boat suits your needs well.
JeffN
Well-Known Member
Thought about doing this with my '25, in the end I replaced with another I/O. Couldn't be happier. I was a little concered with how my boat would handle with an outboard on a bracket. Brackets did not exist when my boat was built so I was unsure about the finished product, why get stuck with something that might be a dog when finished. The I/O replacement will be less expensive also. Check out your I/O options while you are looking at the outboard. What size is the motor thats in it?
i/o power replacements are as cheap as ever. i'll agree about the omc part , as they weren't the best thing they ever built. i think with alittle work on the transom (which might need it anyway) you can go with a old school volvo-penta drive and be almost maintenance free. i have a 85 that has never been apart and the seals hold just fine. plus the gearcase oil is 10-30w motor oil. if you mount a bracket and are off just a little bit, that boat will handle like crap.
gradyfish22
GreatGrady Captain
I do agree, staying with an i/o would be way cheaper. I would have the transom worked on and reglassed and stringers checked. I've heard stories of i/o Grady's having more issues with stringers then outboard models, guess it depends on the model and year as well as upkeep. My buddy has a mid 80's 22 that he repowered and has an i/o. He had the transom redone and the engine replaced, do it at the same time. You need the engine out to redo the transom anyways, so have both done at once if you go that route and stay with the I/O. Hopefully you can find someone to do all the work for you at one location.