4.3omc i/o and motor conversion to mercruiser

[vdomt]

i have a 1987 searay 265 sedan bridge cruiser with twin omc cobra i/o.s and i want to repower with mercruiser. has anyone already done this or know what all is involved? will i have to plug and recut the transom? will my existing wiring for gauges and such have to be redone? i'm thinking of complete engine and outdrive packages. is there a better way?

 

[futz]

Re: 4.3omc i/o and motor conversion to mercruiser

i think all you got to do is take everything out and install the motor and drive same cutout. Gauges the same. i even think you can make the shift, throttle cables work.

Steering cable " maybe different " ?

 

[jtybt]

Re: 4.3omc i/o and motor conversion to mercruiser

I'm probably going to re-power a friends '87 OMC(Cobra) 2.3 l with a 4.3. The motor is coming out of a junked out boat. If the motor runs we'll probably go ahead with the swap. Not sure if we'll swap transom assemblies...which ever is better. I've swapped out mercs before so if I swap the OMC's, I'll be able to tell you what she looks like. I have merc transom assm laying around so I can match up the inner(which is light).

 

[HT32BSX115]

Re: 4.3omc i/o and motor conversion to mercruiser

i have a 1987 searay 265 sedan bridge cruiser with twin omc cobra i/o.s and i want to repower with mercruiser. has anyone already done this or know what all is involved? will i have to plug and recut the transom? will my existing wiring for gauges and such have to be redone? i'm thinking of complete engine and outdrive packages. is there a better way?

Howdy,

If your 87 Searay indeed DOES have an OMC Cobra installed, you can simply remove all the OMC "stuff" and install the Mercruiser of your choice.

If you decide to install a Bravo drive, you will have to drill 2 additional holes for the 8 studs the Bravo has. If I'm not mistaken, The Alpha Gen II's also have 8 studs. Otherwise the cutout is the same and the all the stud/bolt holes will match up.

You may have to relocate the engine mounts slightly. I simply used marine epoxy mixed with milled fiberglass to fill the old holes and then redrilled the new ones.


You also need to inspect your transom carefully for water intrusion and rot.


While you might be able to use the wiring harness from your OMC with most Mercruiser engines, I removed my OMC harness and used the Mercruiser harness because was in FAR better shape and it had the additional wiring for the low oil/high temp/drive lube alarm circuit.

You could just add the additional wiring if you like.


OMC King Cobra Cutout In my 87 FourWinns 211 Liberator

After cleaning it up, re-glassing the flat areas and getting ready to install the 1997 Mercruiser Bravo III

There is NO change in the "cut-out" "other than the 2 additional holes"

Cheers,


Rick

 

[Ducatinut]

Re: 4.3omc i/o and motor conversion to mercruiser

PM sent, but there's now an alternative to yanking everything Cobra and replacing it with Merc parts.

Times they are a'changin'.

 

[HT32BSX115]

Re: 4.3omc i/o and motor conversion to mercruiser

PM sent, but there's now an alternative to yanking everything Cobra and replacing it with Merc parts.

Times they are a'changin'.

And.....that alternative is............... (?)

 

[Lou C]

Re: 4.3omc i/o and motor conversion to mercruiser

thinking of the SEI conversion....Alpha to Cobra gimble housing??
I'd like to see how well it works first....the shift mechanism is pretty different from the Cobra to the Alpha....if it works...great!

 

[sea wolf]

Re: 4.3omc i/o and motor conversion to mercruiser

PM sent, but there's now an alternative to yanking everything Cobra and replacing it with Merc parts.

Times they are a'changin'.

Yea, what's with the pm? There are plenty of Cobra owners here, myself included, who would like you to elaborate on this new conversion. How 'bout sharing with all?

 

[futz]

Re: 4.3omc i/o and motor conversion to mercruiser

I'm always open to new info, isn't that why we all are here.

 

[KRH1326]

Re: 4.3omc i/o and motor conversion to mercruiser

Bubba1235 is the man with the inside track. I will not spill the beans without his permission, but watch his project posts this winter.

 

[Ducatinut]

Re: 4.3omc i/o and motor conversion to mercruiser

Sorry, didn't mean to offend. Quite a while back, I asked the moderators about discussing the conversion kit on the forums. There was a bit of reservation among them and I didn't want to rock the boat or cause any problems. I have tried to use the PM system to avoid violating the terms of use and to avoid looking too commercial.

But, since you asked - SEI does have a conversion kit that's being seeded to a select group of dealers. I am one of the original designers and testers of the conversion and I have to say that there is NO good reason not to use it. I have well over 150 hard hours on the prototype or production kit (the testing was done on a 24' cruiser that weighs about 5K in the water with a 260HP V8). If you want to see the conversion in person, I keep the boat in the water at Norris Lake in Tennessee and I'm happy to give rides and demos (provided you split the gas and beer money ).

It's WAY over-designed and very robust. There are no modifications required for the transom assembly and the boat can easily be converted back to the Cobra, or even a Volvo SX, should you actually want an over-priced and under-supported drive.

The conversion (including labor), should cost no more than about $2500-3000. The kit is about $350 retail and the drive will be modified for free if you buy it from SEI or one of their dealers. Expect about 6 to 8 hours of labor by a tech has done the install before. I can do one with my tech in less than 3 hours.

The only real limitation is the drive. Right now, only the Alpha style drive is supported (Gen II to be specific) so you are limited to 300 HP. (If someone is willing to donate a Bravo bell and drive upper, I'm certain that it can be adapted as well)

I'm happy to answer your questions about the kit. If your reservation is based on the quality of SEI's parts, then don't waste your time. Their drives are bulletproof and QC is of utmost importance. I'll buy an SEI drive before an OEM part, because they're better made and the factory support is better, IMHO.

My disclosure: I get nothing if you don't buy the conversion kit from me. I get no royalties or kickbacks as the manufacturer has full rights to the product and design. We weren't out to make a bunch of money, but to get back in the water with a solution that works and doesn't break the bank (or the marriage). We partnered with SEI, because they were the most likely to bring a quality product to market and highly unlikely to bury any competition (they ARE the competition).

Again, if I've offended anyone, my apologies.

Chris

 

[KRH1326]

Re: 4.3omc i/o and motor conversion to mercruiser

Oooh,

Who REALLY has the inside track NOW!!! Ha Ha

That is awesome for the cobra, will there be one that will liberate me from the Electric Shift, down the road?

 

[HT32BSX115]

Re: 4.3omc i/o and motor conversion to mercruiser

That is EXTREMELY COOL!

I might have considered it with my 211 Liberator.......(wait a min I would have had to keep the 460......

NEVER MIND!!)


I don't think anyone will be "offended" by your illustration and promotion of the SEI conversion. (At least I'm not!)

This is what everyone has been waiting for I think. It will solve a LOT of problems people have with replacing the Cobras. (It won't solve the engine problems though but..... ONE PROBLEM AT A TIME!!)

Firefox + Adblock = No Annoyances

True........ Make it Firefox + Adblock running on top of a major distribution of Linux and you get .....NO MS ....which is even better!!....And then add OpenOffice and GIMP (but there I go digressing again!......somebody slap me!!!!

Cheers,



Rick

 

[Ducatinut]

Re: 4.3omc i/o and motor conversion to mercruiser

Oooh,

Who REALLY has the inside track NOW!!! Ha Ha

That is awesome for the cobra, will there be one that will liberate me from the Electric Shift, down the road?

I personally doubt that there will be anything for the stringer drives. There's just too much engineering and tooling for too little return. There are some great boats out there that have stringer drives in them and I suspect that the only reasonable solution is to keep the old drive system alive. For every electric shift horror story I've heard, there's someone talking about how dependable it was...

For what it's worth, there's a fella out west who has a stringer-powered boat and a cheap/free Cobra transom assembly who is looking at a two step conversion to SEI power.... I think he's nuts, but I made him promise to keep me posted on his progress.

Fair winds,

Chris

 

[Ducatinut]

Re: 4.3omc i/o and motor conversion to mercruiser

That is EXTREMELY COOL!

I might have considered it with my 211 Liberator.......(wait a min I would have had to keep the 460......

NEVER MIND!!)


I don't think anyone will be "offended" by your illustration and promotion of the SEI conversion. (At least I'm not!)

This is what everyone has been waiting for I think. It will solve a LOT of problems people have with replacing the Cobras. (It won't solve the engine problems though but..... ONE PROBLEM AT A TIME!!)

The poor 460 - it's a great engine for a boat, other than being thirsty (and having no support). Don't forget that Chris Craft used 427's (the predecessor to the 460) for many years in their big boats. Gobs of torque, indestructible, and beautifully smooth.

As far as offending anyone - I don't want to be *that guy* and I try to make sure I follow the local etiquette. The same reason I prep my boat in the parking spot and not at the ramp and why I don't throw wakes at little boats or folks fishing, even if I'm in open water.

True........ Make it Firefox + Adblock running on top of a major distribution of Linux and you get .....NO MS ....which is even better!!....And then add OpenOffice and GIMP (but there I go digressing again!......somebody slap me!!!!

As far as that goes, I'm an OS X user, so I get the best of both worlds... a *nix underneath and an interface that doesn't make me crazy... And if I want to open a terminal session, it's a couple of keystrokes and I get a happy bash session looking at me...

Fair winds,

Chris

 

[HT32BSX115]

Re: 4.3omc i/o and motor conversion to mercruiser

Don't forget that Chris Craft used 427's (the predecessor to the 460)

I thought that was the 429?


This thing ran GREAT with the 460. I don't have any real complaints about how it used to run..... but it sure runs great with the 454+Bravo III now....I still cannot believe how fuel efficient it is.

I'm an OS X user, so I get the best of both worlds...

hmm...well to a certain degree...except that you have pay a fairly pretty penny for it and you have to use their hardware......I can use any hardware (including YOUR hardware!) and it's completely free...as are all the updates and upgrades.......And I can make it look like MS Winblows or or a MAC..(isn't that some sort of a truck?..........JUST KIDDING!!!!)


Just bought myself a new Lowrance HDS5 (runs Linux) I also have a new Garmin GPS navigator.......(Runs Linux) I have a Netgear router sitting on the desk.....(Runs Linux), My wife wants a new Palm "PRE" (runs Linux)..... She also wants a TIVO (runs Linux).....Just bought myself a cool ethernet camera (runs Linux) It's everywhere! (including my desktop computer!)

Above all, I love having a choice.....There I go........digressing again.......

 

[vdomt]

Re: 4.3omc i/o and motor conversion to mercruiser

thanks for all the good input! I've worked on boats for years but never this big of a job so i'm a bit intimated. my major problem is i can't keep the omc drives where they will shift so the sei conversion is very interesting because it would be way cheaper and presumable solve my shifting problems. i would be interest in seeing your prototype installation. how could we set that up? what happens if later i do decide to replace the motors would i have to use omc or could i easily ie cheaply use mercruisers? ht32bsx115 your pictures look great You did an outstanding job. Want to do another one?

 

[Ducatinut]

Re: 4.3omc i/o and motor conversion to mercruiser

I thought that was the 429?

Umm... You're right... Confused it with the FE engines. :redface: Still a great motor, if you can afford to feed it..

hmm...well to a certain degree...except that you have pay a fairly pretty penny for it and you have to use their hardware......I can use any hardware (including YOUR hardware!) and it's completely free...as are all the updates and upgrades.......And I can make it look like MS Winblows or or a MAC..(isn't that some sort of a truck?..........JUST KIDDING!!!!)


Just bought myself a new Lowrance HDS5 (runs Linux) I also have a new Garmin GPS navigator.......(Runs Linux) I have a Netgear router sitting on the desk.....(Runs Linux), My wife wants a new Palm "PRE" (runs Linux)..... She also wants a TIVO (runs Linux).....Just bought myself a cool ethernet camera (runs Linux) It's everywhere! (including my desktop computer!)

Above all, I love having a choice.....There I go........digressing again.......

I don't disagree with you. I use Linux a lot - for remote router installations, for servers, and for desktops where it makes sense. I'm a big fax of OS X, because it *just works*. It doesn't hurt anything that I've used a Mac for my primary machine since the OS 6.0 days. Even with the transition to BSD, Apple has done a good job of retaining the look and feel that I like and not changing stuff just to change it...

Ultimately, I agree with you - the key is *choice*.

Fair winds,

Chris

 

[Ducatinut]

Re: 4.3omc i/o and motor conversion to mercruiser

thanks for all the good input! I've worked on boats for years but never this big of a job so i'm a bit intimated. my major problem is i can't keep the omc drives where they will shift so the sei conversion is very interesting because it would be way cheaper and presumable solve my shifting problems. i would be interest in seeing your prototype installation. how could we set that up? what happens if later i do decide to replace the motors would i have to use omc or could i easily ie cheaply use mercruisers? ht32bsx115 your pictures look great You did an outstanding job. Want to do another one?

To be honest, the goal would be to look for a dealer who has a grizzled veteran that can make your Cobras work. They're not bad drives, but support is a challenge. However, if you've been down that road...

I'm not sure how to demo the conversion, other than in person. My suggestion would be to contact SEI (Sterndrive Engineering) and ask for Justin. He should be able to point you to a local dealer who can help you out. If there's noone who can or will work with you, I'll make every effort to help you out.

In regards to the engines, keep in mind that most sterndrive engines are just "marinized" auto engines. In most cases, the engines just have the freeze plugs replaced with brass pieces and a truck-type cam spec'd (yeah, yeah, there's a few other details, but these are the most apparent).

Most of the major components are still available (manifolds, trim pumps/motors) and the maintenance stuff is a non-issue as both Merc and OMC (and Volvo, etc) are using the same basic parts, just with their own part numbers. I use napa filters, plugs, etc (but, always marine for ignition or for anything that is a spark or fire hazard). A little bit of legwork will reveal a lot of similarities between the brands.

I'll see if I can get some additional photos of the conversion up on the web. I also have a couple of videos that show the conversion in use. Let me think a little bit and I'll see what I can come up with...

Fair winds,

Chris

 

[Ducatinut]

Re: 4.3omc i/o and motor conversion to mercruiser

Hello, all--

I posted some of my pictures and videos on Photobucket this morning. I'm not very fluent with this stuff, so if it doesn't initially work, please be patient. Of course, suggestions are MOST welcome.

Here's a picture of the Alpha-type drive installed on a Cobra transom:

A wide angle shot:

As you can see, my development mule is a decent sized old beast. It's among the last of the old school Four Winns cruisers - thick fiberglass, huge stringers, massively overbuilt. And heavy.

A mandatory off the stern shot:

A short video while underway at speed - the quality is poor and I am not skilled at taking videos (was done with my el-cheapo digital camera), but you can clearly see the SE116 drive installed on the boat:



Here's a shot of us pulling a 2-person tube at Norris Lake:

Performance on this boat is close enough to be a non-issue. The gear ratios between OMC and Mercruiser are nearly identical and the relevant dimensions of the drive ARE identical (within fractions of an inch).

The kicker? With a small adapter bushing that I got from Delta Prop here in Cincinnati, I was able to reuse my "Cobra-Type" prop with my new drive.

There's a bunch more photos and some other videos in my album, feel free to check it out:

http://s65.photobucket.com/albums/h213/tautog/Cobra Conversion Kit/

Fair winds,

Chris