I/O to Inboard conversion

Has anyone ever done anything like this before?

We have an older I/O, 18ft powered by a 350 Chevy (320 hp) that was possibly converted from an outboard at some stage, but I'm not sure.

Last night I discovered a major oil leak, oil in the bilge and none in the engine. I'm not sure where it is coming from, under or behind the engine somewhere probably which basically means we may have to pull the motor to fix it since there is next to no room under there. I'm pretty gutted we've only been out 2 days this year and we have another massive fix to do now. Seems like we fix this boat two or three days for every one on the water.

The stern leg isn't in the best condition and will probably be quite expensive to rebuild. The power tilt has never worked because someone burned out the pump before we bought the boat. So the advantages of having an I/O pretty much don't exist in this boat any more.

I am trying to figure out if it makes sense to convert to a V drive, and also find out if there are any pit falls to watch out for, or any good advice out there. D drive might be easier but I don't want the motor in the middle of the boat. We would need a new trailer but our current one is pretty rough anyway and sucks for towing on the open road, so it would be nice to get a new one.

The wake is almost like a CC2001 currently, solid and steep. As a V drive I think this wake would be incredible. This boat weighs a lot dry, about the same if not more than a modern 21 foot wakeboat I'd imagine. We rode on the weekend with 8 people on board and no additional ballast, the wake was nearly knee high and clean 70 - 75' back at about 22 mph. Not bad for an I/O.

While this is not really a project I want to start in the middle of Summer we can't ride with no motor so it would give us a chance to pull up the floor and replace at least some of it, as well as fix the leaks in the front ballast tank and maybe add some new ones and new more effective scoop plumbing. Plus I can look at fixing some cosmetic things that have been ignored for a while and change out the stereo that doesn't work for one that does.

After a quick search this morning finding the V drive might be the big hurdle as I couldn't find any used ones for sale on local auctions, although we might find one new somewhere. I will also need a transmission if I want her to go anywhere when we're done but I don't know anything about what kind or size.

Anyway, I'm just looking for advice at this stage, all comments welcome. I'll get some pictures some time soon.

Oh yeah, how do you figure out where to put the tracking fins?

I can see the sense of accomplishment from tackling this mechanical quest, but you will pour money and time into it and it will not make practical or financial sense. An older 18' I/O is not going to be worth much and an older I/O converted to a v-drive is going to be worth about the same. You will be way better off patching her up riding it or take the money you are setting aside for the upgrades and trade for a used inboard.

There are many more issues to think of too. Steering, tranny mounts, motor mounts, cooling, exhaust.......

That's true, if I lived in the states I probably wouldn't even consider a conversion, but used inboards don't come cheap down here in NZ ($12,000 just to ship a boat from the states is a common figure apparently) and we already have a ton of money in this boat. I think we could get some coin for the stern leg too.

Far as I can tell the motor should be able to sit on the mounts it already has, just turned 180 degrees, will be easier to tell once it's out of the way if it does need to be pulled. Cooling and exhaust shouldn't be a problem just need to measure up and cut some holes for the raw water pickup and pipes and swap the headers over (I think).

The steering sucks, I'd way rather have a cable and rudder (or double rudder ala Epic) set up than the bent hydraulic whatever it is we have now.

Tranny and mounts I have no idea about, I haven't actually seen inside a V drive, only inboard ski boat I've ever been on was a D drive.

Thanks for the input I appreciate any help I can get, or constructive criticism.


(Message edited by jtnz on February 10, 2009)

sounds like you will have the next 2 years of your life set aside tackling this project. good luck though and post up pics of your progress.

Haha hopefully not quite that long. I have to find the oil leak first and determine if I even have to pull the motor, but it could probably use some cleaning up at the very least.

Hi Jos. I've done many weird and wonderful conversions over the years. (On cars and other things, but not a boat yet) I have enjoyed them all and they have all been frustrating at times. From an economic point of view it has never been the cheaper fix.
Here is, honestly, how you budget for it. Figure out the cost of all the parts ahead of time and the custom fabrication and hand work. Do not be low on your guesses. Pick the high range. When you get that total with everything at the high end - double it. If you have that much extra cash you want to spend feel comfortable starting. You won't be high on your estimate. Stopping in the middle of this kind of project gives you $0.00 back.
If all that's fine just remember jason's time estimate.

Put the tracking fins at about the centre of mass. Start with one, then add another or two if you need more.

(Message edited by rallyart on February 10, 2009)

Make sure your trailer will work with tracking fins on the boat before you put them on. Or raise the bunks to accomodate the clearance.

And I'd agree with the conversion estimates here. I like Art's formula for estimating the cost as well. Unfortunately, your resale is going to be the virtually the same. The issues that arise during a conversion like this could be endless. Not to discourage you, but thats how I see it.

Your engine: first thing that pops in my mind is the rear main seal. personally, I'd yank the engine you got, tear it down and drop it back in. You could be on the water in a week tops.

The conversion is a cool idea, but poses many issues.

I'm not exactly sure what you expect to gain by going to a V-drive. Inboards do have some inherent advantages when towing a skiier or wakeboarder but the wake is mainly a product of the hull. Changing your drive system just isn't going to make that big a difference.

Onto the conversion at hand, you've got a big hole to plug the the back of the boat. They make that pourable stuff for transom repair but it's pricey. In your case though it may be better than completely redoing the transom. Your current engine mounts will probably not work. A V-drive angled a lot more than most I/Os. You're probably going to have to fabricate some mounts on your own. You may be able to get away with using your mounts on some sort of spacer.

If you do go through with this, try to get some pics.

Yeah I thought rear main seal too

We will need a new trailer if I do this, the one we have now has rollers all the way up the keel, that's never gonna work. Although apparently I might not even need tracking fins.

I thought I/Os produced soft wakes and V drives were the business haha. At least that's about all I see on here.

So far just about everyone has made a fairly discouraging albeit accurate statements (not a bad thing) which has got me thinking. Double the budget is probably what we paid for the boat in the first place, not to mention all the replacement parts and hours we've put into it already. I wouldn't be surprised if this boat has had $50k spent on it during it's life.

While it would be an awesome thing to do it would also be terribly expensive and time consuming for not much gain. Maybe I should just sit on this boat, ride it and then get something purpose built in the future... it really does have a good wake as it is, but it is a work horse not a show pony that's for sure. I don't think I will have the time or the money to throw at it to make it the latter.

I'm gonna have to weigh up the difference between getting everything fixed as it is now versus changing everything over to a full inboard. I like that with a V drive I can surf too, I think she would throw a pretty sweet surf wake, so it would add some versatility. That being said I'm spoiled for choice here a couple of mates surfed both coasts in a day last week just to say they'd done it so I can surf regardless.

Thanks again for all the posts whether encouraging or discouraging it's all good informative stuff so much appreciated.

(Message edited by jtnz on February 11, 2009)