SoCal Jet Boats

Tech Talk => I/O's => Topic started by: Luckie Stiff on January 20, 2008, 05:17:12 PM

Title: Jet to I/O conversion?
Post by: Luckie Stiff on January 20, 2008, 05:17:12 PM
Could this be done? Seems like once you glassed in the intake hole it'd be simple math. With the price of fuel getting higher by the day this seems like it may be a logical thing, build a nice high HP small block, add a good outdrive and you're going faster than your jet, and using half the gas. Hmmm, anyone know where I can find a good used outdrive unit? >:D
Title: Re: Jet to I/O conversion?
Post by: Nordie on January 20, 2008, 06:10:26 PM
<~~~my nordic is a jet style hull with i/o...omc outdrive will fill that hole nice but they cant take a whole shit load of power...i'll be testing that theory this summer though i'll keep you posted
Title: Re: Jet to I/O conversion?
Post by: hotrod56cars on January 20, 2008, 10:32:58 PM
You shouldn't own a jet boat for any of the following reasons:
gas mileage





Keep the ropes from the props!
Title: Re: Jet to I/O conversion?
Post by: Warlock on January 21, 2008, 03:53:30 PM
Why not get more room in your ride and be faster then both of them and hang an outboard on the back...They sound a whole lot better to ;D
Title: Re: Jet to I/O conversion?
Post by: OC2Vegas on January 21, 2008, 04:40:43 PM
Why not get more room in your ride and be faster then both of them and hang an outboard on the back...They sound a whole lot better to ;D

Your high as a kite! NOTHING NOTHING NOTHING sounds better then an unmuffled BIG BLOCK!

Crack kills, lay off the pipe! >:D
Title: Re: Jet to I/O conversion?
Post by: Nordie on January 21, 2008, 06:07:58 PM
Your high as a kite! NOTHING NOTHING NOTHING sounds better then an unmuffled BIG BLOCK!

Crack kills, lay off the pipe! >:D

now thats funny, but i couldnt agree more...with the whole better sounding thing...nothing beats a V8 sound or the smell of high octane fuel
Title: Re: Jet to I/O conversion?
Post by: Warlock on January 22, 2008, 07:45:52 AM
New you'd like that comment!  ;D Nothin' like the smell of 2 stroke oil in the mornin'! ;)
Title: Re: Jet to I/O conversion?
Post by: Brad @ SCJB on January 22, 2008, 07:48:41 AM
New you'd like that comment!  ;D Nothin' like the smell of 2 stroke oil in the mornin'! ;)

nothing worse then an outboard cruising through the channel when theres no breeze!
Title: Re: Jet to I/O conversion?
Post by: OC2Vegas on January 22, 2008, 08:39:30 AM
An outboard boat just looks like someone didnt have enough time to finish the jet boat and just threw on what ever they had lying around! What a waste of a perfectly good hull >:D ;D
Title: Re: Jet to I/O conversion?
Post by: old rigger on January 22, 2008, 10:03:18 AM
Bottom line is a prop boat will out perform a jet in all areas, all day long. Jets are fun, I've owned more than I can count, but an I/O, v-drive or an outboard will spank most of em. And they'll do it with far less hp.
Back in the 80's at Advantage we took a Banshee, which was an eliminator knock off designed for a jet (and they're a turd with a jet unless you're running big, BIG horsepower) and we ran a basically stock sbc, single carb, low rise manifold and hooked it to a OMC cobra outdrive. We ran 116 mph, the APBA record still stands after 20 years. Try running that speed with a jet and a small block, hell try doing it with a big block. the Banshee outboards worked well too, stock 220 merc, they'd run 72-73 all day long. The banshee's with a stock jet set up, set back pump, shoe, rideplate and so on but with a stock BBC, would blubber along and try to squeeze out a miserable, very wet 68 mph.

I wish I still had my '65 Tahiti that I restored in the late 80's. Had a 125 merc hanging off the transom, it was a fun boat. My friends nicknamed it the jet killer, 'course I'd only race pretty much stock jets, I'm not an idiot, but they never had a chance and couldn't figure out why their 80 mph jet boat just got spanked but an old Tahiti. lol

I/Os, jets, outboards and v-drives...I like 'em all.  ;)
Title: Re: Jet to I/O conversion?
Post by: wanabe on January 22, 2008, 04:19:57 PM
Bottom line is a prop boat will out perform a jet in all areas, all day long.
I think that's not contested; jets are simply  8) coooooooool  8) ; looks, sound, etc.
Title: Re: Jet to I/O conversion?
Post by: OC2Vegas on January 22, 2008, 04:24:42 PM
An outboard boat just looks like someone didnt have enough time to finish the jet boat and just threw on what ever they had lying around! What a waste of a perfectly good hull >:D ;D

Im just starting shit! ;D

I think that's not contested; jets are simply  8) coooooooool  8) ; looks, sound, etc.

exactly!
Title: Re: Jet to I/O conversion?
Post by: Nordie on January 22, 2008, 06:09:04 PM
hmmmm im liking that...healthy small block with omc outdrive jet style hull and over 100 wait wait...i have a jet stlye hull not (banshee) but still descent hull omc outdrive and purchasing a healthy small block soon hmmmmmmm im liking the sound of this...it's all good, like i said omc outdrives you half to make the hole in the transom bigger so that makes things easier, now on to plugging that big hole in the bottum and you got yourself a different boat and maybe some gas at the end of the day
Title: Re: Jet to I/O conversion?
Post by: old rigger on January 22, 2008, 06:24:30 PM
OMC's take the same size hole as a Mercruiser, have for over 20 years. The old OMC's that took the big hole, bigger than the one for a pump, aren't as good as the newer ones. Tough, dependable, but not built for speed. :)
Title: Re: Jet to I/O conversion?
Post by: old rigger on January 22, 2008, 06:25:21 PM
I think that's not contested; jets are simply  8) coooooooool  8) ; looks, sound, etc.

They're all cool to me.  ;)
Title: Re: Jet to I/O conversion?
Post by: hotrod56cars on January 22, 2008, 06:44:59 PM
OMC's take the same size hole as a Mercruiser, have for over 20 years. The old OMC's that took the big hole, bigger than the one for a pump, aren't as good as the newer ones. Tough, dependable, but not built for speed. :)

Which one is better of the two, OMC or Mercruiser? Thanks.
Title: Re: Jet to I/O conversion?
Post by: old rigger on January 22, 2008, 07:10:58 PM
I'd have to give the nod to Mercruiser. OMC jumped on their bandwagon 20 years ago when the copyrights expired for Merc. The Cobra was a clone, kinda, of the Merc except it was a piece of shit. They re-tooled and came out with the king cobra, that's what we raced, and we only raced it because they gave it to us. OMC wanted a record to help promote the new and improved King Cobra. That unit was tough as nails, we ran it and set the record and then two years in a row ran the Mississippi race. That one is/was (I don't know if they still run it) 1000 miles in 2 days. On the river, through 5 or 6 states, not on a track going in circles. A hell of a race. The first year we got a big fat DNF, broke on the second day and I can't even remember what the hell broke lol, second year we won. Never had a moments problem with the OMC drive. But lets face it, Mercruiser had been the leader for a long time. I've had a few, have an old one now, and like 'em.

Oh the boat died at the Parker enduro when it was, I think 7 hours, maybe 5 I can't remember what it was in the late 80's. Harry caught a sponson in the FIRST turn, ripped the sponson off, flipped the boat and it sank. We got it up I think 3 days later.
Title: Re: Jet to I/O conversion?
Post by: bkplesh on January 22, 2008, 07:12:51 PM
mercruiser >:D
Title: Re: Jet to I/O conversion?
Post by: Warlock on January 23, 2008, 02:11:10 PM
Since they haven't made OMC's in 10years parts are getting hard to come by...
Title: Re: Jet to I/O conversion?
Post by: SLCKREG on January 23, 2008, 02:32:11 PM
I had horrific luck with the omc I owned.
Title: Re: Jet to I/O conversion?
Post by: bkplesh on January 23, 2008, 02:47:30 PM
just one of a few >:D
Title: Re: Jet to I/O conversion?
Post by: Toes on the Nose on January 23, 2008, 05:05:48 PM
I've heard bad things about the OMCs I have a Volvo/Penta and it hasn't given me any trouble yet. Let's just hope it holds up when I put a stout Small block in front of it. If you're gonna go Mercruiser, I would suggest going with a Bravo. My friend has a Bravo on his 23' Essex w/ a 502 and I've beat the hell outta that thing in heavy chop and it holds up well.
Title: Re: Jet to I/O conversion?
Post by: jrork on January 23, 2008, 08:26:54 PM
I/Os, jets, outboards and v-drives...I like 'em all.  ;)

Ditto rigger.  Clampons are the norm up here in the salt followed closely with the I/Os.  Either way, I like them all too.......
Title: Re: Jet to I/O conversion?
Post by: Nordie on January 23, 2008, 08:44:19 PM
i agree on the mercruiser deal way better and i got clued in on the omc deal just now...my omc does fine just the tilt mechanism gives me shit but i got a fresh one going in...
Title: Re: Jet to I/O conversion?
Post by: TIMINATOR on January 29, 2008, 01:16:24 AM
An alpha setup with a decent small block will run well on top end, ride better, and use less fuel too. Now the downside....  although you can buy the Merc Alpha copies cheaply, and they will take more HP than the Merc, the problem is finding a complete transom assembly to mount it on. New ones are pricey! Downside two; jets push the boat from the floor where the intake is glued in and so the transom needs minimal strength. A Merc I/O pushes the boat from the transom, and the transom also carries the weight of the mount assy. and the lower unit too, the hole size in the transom is of little importance if the proper reinforcement is not done. I have seen where peeps have glassed in the jet /transom hole, mounted a setback plate/jack assy, gone to the lake and almost IMMEDIATLY started ripping the transom from the top down. Neither boat sank, but it could have been close....  Better talk to someone that knows what they are doing before starting this deal. Just as an example, before I bought my 25' Eliminator Daytona, I had a 24' Daytona, it had a 260 HP/350 small block in it, and it ran about 50 MPH. I installed a Comp 280 cam,Performer RPM airgap intake,big block risers on the stock manifolds, and thru transom exhaust. Speed increased to 62 MPH, the new buyer added Holley systemax heads and cam and now runs around 68 MPH, on regular gas. Not bad for a 24' boat! It was at the Eliminator regatta on Havasu this summer and surprised quite a few folks. Plans are for either a 406 or a 434 shortblock,with hoped for speeds of about 75 or so. Best of all the insurance company still thinks it is a 260 HP/350!  P.S. the aftermarket Alpha copy outdrive has been troublefree for 3 years now.  The boat is black with pink and blue stripes and can be seen at Havasu or Lake Plesant AZ.  TIMINATOR
Title: Re: Jet to I/O conversion?
Post by: TIMINATOR on January 29, 2008, 01:19:41 AM
To clarify what happened to the jet conversions, one installed an Evenrude 150 HP weed wacka, and the other had a Black Max 175. TIMINATOR
Title: Re: Jet to I/O conversion?
Post by: UNDONE on February 28, 2008, 08:30:26 PM
Not mercruisers fault but two of my friends have had some issues with their outdrives. One spent 5000 getting it fixed. The other is still broken with a price tag of $3000 to fix.

The first being the Mercruiser Black Hawk in the high-freeboard 1995 22' daytona (running mid 80's with a 415HP 502 EFI). Blackhawk was in for routine maintenance, apparently the shop took apart the drive to grease everything and put something back in place so that caused the shaft coming straight down in the drive and the prop shaft to bind. It SHEARED the shaft going straight down through the outdrive. PW_tony has seen this boat


The second being a Teague Custom Marine Bravo 1 in a 20.5 Carrera Elite (running high 80's with a 720HP Teague Custom Marine 502 built 5 years ago).

This one needs new gimbal ring assembly among many other things. Apparently not made for that much power. Still runs but is real sloppy. Engine sounds mean as hell, drive thunks real hard
Title: Re: Jet to I/O conversion?
Post by: beerjet on November 23, 2008, 11:09:51 PM
Do to the random gum flapping , the question was never answered . My understanding is that the hole the intake leaves is what drives everyone from doing this conversion .

My idea: To Balsa wood the entire bilge and then glass the bottom . Not in the order exactly but I think the wood would be a huge help in strengthening that area back up . Speed coat the bottom , wood inside , badda bing , badda boom . Yay or nay .

-beerjet-
Title: Re: Jet to I/O conversion?
Post by: GT Jets on November 23, 2008, 11:30:48 PM
Why not just build an aluminum plate and bolt and epoxy it in like an intake? :sly:

Aluminum can be speedcoated, you could plug that hole for a hundred bucks in a weekend...The problem remains, a transom of approx. 2-1/8" still needs to be fabricated. That's where the mad skills come in...Can be done, but requires some laminating talents.

GT
Title: Re: Jet to I/O conversion?
Post by: beerjet on November 23, 2008, 11:49:39 PM
Why not just build an aluminum plate and bolt and epoxy it in like an intake? :sly:

Aluminum can be speedcoated, you could plug that hole for a hundred bucks in a weekend...The problem remains, a transom of approx. 2-1/8" still needs to be fabricated. That's where the mad skills come in...Can be done, but requires some laminating talents.

GT

I just figured the wood looked pretty and would add some strength is all .I do remember that the transome would need to be beefed up considerably too . I picked up a sheet 1/4 aluminum plate about the size of an intake for $30 bucks so that does sound like a waaaaaay better way to go (https://forum.socaljetboats.com/proxy.php?request=http%3A%2F%2Fwww.socaljetboats.com%2Fcpg%2Falbums%2Fuserpics%2F10034%2Fidea_2.gif&hash=feb8bb07af45546811fec675cf181609b33cb672)

-beerjet-
Title: Re: Jet to I/O conversion?
Post by: GT Jets on November 24, 2008, 12:01:25 AM
I think if done right the aluminum would be considerably stronger given the old glass new glass thing. I have only seen a few jobs that give me the warm and fuzzies in reference to overall strength of a major hull repair with glass and wood, but then again, that's not my area of expertise.

A funny thought though, have the bottom of the boat hinged for easy oil changes  O0

GT
Title: Re: Jet to I/O conversion?
Post by: dragdaddyO on August 02, 2009, 07:08:17 PM
New to the sight but was reading this and one thing to remember. I/O drives require a lower idle speed than jets so when choosing a cam you might want to use a 118 degree centerline on big cams.
Title: Jet to I/O conversion?
Post by: damstarr on February 09, 2012, 10:00:47 PM
Anybody go the other way? I/O to jet? Pros/Cons????
Title: Re: Re: Jet to I/O conversion?
Post by: BIG JOHNSON on February 09, 2012, 10:35:20 PM
Anybody go the other way? I/O to jet? Pros/Cons????

Sounds like a lot of work.

I like this idea.

Sent from my ADR6400L using Tapatalk
Title: Re: Jet to I/O conversion?
Post by: wickwine on July 04, 2013, 06:56:03 PM
Anyone have any pics of swapping from the jet to I/O? Transome work, intake glassing? I have a 1980 condor 5.5 with a berkeley 12je and a mercruiser 260, I think I could get ahold of an alpha 1 for dirt cheap.. How much work would be involved.. I think I'd be getting in way over my head but I live in the ozarks in mo and my boat will be a lake boat and I'd love to own all those big 30 plus footer race boats around there. I'd be hilarious to see a lil ole jet boat with a sbc and a I/o hit a Hundo coming out of the no wake zone
Title: Re: Jet to I/O conversion?
Post by: redmond572000 on July 06, 2013, 08:03:22 AM
Anyone have any pics of swapping from the jet to I/O? Transome work, intake glassing? I have a 1980 condor 5.5 with a berkeley 12je and a mercruiser 260, I think I could get ahold of an alpha 1 for dirt cheap.. How much work would be involved.. I think I'd be getting in way over my head but I live in the ozarks in mo and my boat will be a lake boat and I'd love to own all those big 30 plus footer race boats around there. I'd be hilarious to see a lil ole jet boat with a sbc and a I/o hit a Hundo coming out of the no wake zone

Check out Ky0atk posts! I believe his bahner was already a I/o but he rebuilt the entire transom and cut everything in from scratch! He has a lot of pics and great info!
Title: Re: Jet to I/O conversion?
Post by: spdbk1 on October 15, 2019, 12:28:44 AM
have complete bravo 1 outdrive transom shield gimble rams drive pump 3000.00 949 683 3120 text me for pics
SMFPacks CMS 1.0.3 © 2026