OMC SEI Conversion

[shep247]

Hey guys,
I posted the When to Cut Your Losses thread ( http://forums.iboats.com/showthread.php?t=364273) a few days ago, and some of you mentioned the option of doing the OMC to SEI outdrive conversion. I'm going to take your advice and proceed in that direction. I'm excited about this adventure I'm about to embark on, but I'm sure I will have many questions for you all along the way.

My first question is how do I know which SEI outdrive to get? I know it depends on the ratio of my old drive, but I don't know what it is. Its a 1991 4.3 OMC engine with the cobra outdrive. Can someone tell me what the ratio is on my old outdrive, or better yet, tell me how how I can figure this out?

Thanks guys!

 

[Fishermark]

Re: OMC SEI Conversion

or better yet, tell me how how I can figure this out?

Thanks guys!

The easiest and safest way is to tell Sterndrive Engineering what you have and what you are doing and they will fix you up. Great people - easy to work with. (I have installed of couple of their drives and am happy with their product and especially their customer service).

 

[mcleaves]

Re: OMC SEI Conversion

Agreed. best thing to do is call them and let them tell you what you need. Then if there are any issues you can leverage their recommendation as a tool to solve it. Plus from everything I have heard they are great with this stuff and you will get it right the first time.

My project boat will be getting an SEI.

 

[flyer4ever]

Re: OMC SEI Conversion

I also called them on what I might need to change over my OMC when and if the time comes and found they were very helpful. I've read alot of info on their product and have found everyone has good things to say about them. I think there will be several folks watching your progress if you go through with the change over. I know I will . Keep us informed please. Thanks Ernie.

 

[zbnutcase]

Re: OMC SEI Conversion

SEI drives have their place-on older low dollar boats that would only fetch 2-3000 in great shape. Hard to beat for the money-even with the gear whine the last 2 I installed had, but they haven't broke yet! 'nutcase

 

[flyer4ever]

Re: OMC SEI Conversion

Nutcase, how about a discription, on how the instalation went. How difficult,what drives can be used, and how about the part about needing to change over the controler (push to pull). How difficult was that, And total cost for the average guy to do. I'll bet that would help all of us that are considering the change. Thanks Ernie

 

[Bondo]

Re: OMC SEI Conversion

Ayuh,... I haven't done it, but from what I've gathered,...
You buy the conversion Kit, which mounts to the gimbel housing,at about $1200. It fixes the mounting,+ shifting issues..

Then you bolt on an Alpha 1, Gen.II drive which you buy for another $1500...

 

[flyer4ever]

Re: OMC SEI Conversion

I thought the conversion kit was $350. then the drive was about $1300. Did I read it wrong? I was wondering if you could use any doner boat with an alpha 1 gen 2 drive. Maybe that was wishful thinking. Ernie

 

[Lou C]

Re: OMC SEI Conversion

If you go onto their website and look in the forums...a guy posted on his expereince in coverting over a Cobra to the Alpha with their kit...it seemed do-able by an average do it yourselfer...the water intake hose aspect (getting it the right length) seemed a bit tricky but that's the only issue I can recall that he mentioned...and yes the coversion kit is like 350 if I recall right....I'd still want to try one of these out on the water if I could first to see how well it shifts (shift just like an Alpha or is there more play in the linkage?) and the noise level....my Cobra still shifts with 2 fingers and it's QUIET compared to other Alphas I have heard....but you really cannot beat that price...anything else and you're into more money than most of these boats are worth...the Volvo idea is great until you realize the conversion from them (700 pivot housing....350 raw water pump....4500--5000 drive) is really too expensive unless you can do it with all used parts....and to convert the boat to all Merc you need a donor boat to change everything over (not a bad idea either if you can do the work yourself)...

BTW the gear ratio on an OMC Cobra with the V-6 is 1.68:1

 

[Lou C]

Re: OMC SEI Conversion

I thought the conversion kit was $350. then the drive was about $1300. Did I read it wrong? I was wondering if you could use any doner boat with an alpha 1 gen 2 drive. Maybe that was wishful thinking. Ernie

One important point I forgot to mention is that the drive has to be modified by SEI for it to work...they can modify your drive or if you buy the drive with the kit they modifiy it for your...you can't just bolt up any Alpha Gen II to it......call them to verify....

 

[flyer4ever]

Re: OMC SEI Conversion

Is the modification anything that can be done by yourself. Just looking to save a few $$$$ Ernie I hope this is info that shep can use too. After all this is his post.

 

[longstand]

Re: OMC SEI Conversion

What about me.. i have an older boat with a regular sterndrive. its not COBRA. nothing. just regular.

do i have any hope of converting my also..

 

[bruceb58]

Re: OMC SEI Conversion

They do not offer anything for a stringer drive and never will. The Cobra uses U-joints and the stringer doesn't have u-joints so there will never be a mod to a sei drive.

 

[Bt Doctur]

Re: OMC SEI Conversion

http://www.sterndrive.cc/pdfs/conversion.pdf

 

[Bondo]

Re: OMC SEI Conversion

i have an older boat with a regular sterndrive.

Regular,..?? Regular,..??
There ain't Nothing Regular about a Stringer drive...
It's a historical artifact,+ little more...
They were Obsolete in 1985,... That's 23 Years ago...

do i have any hope of converting my also..

Sure,... I do it all the time,...
Rip out the entire Driveline, Junk it, Glass in the huge Hole in the boat, cut a new keyhole,...
Then drop in a Complete Mercruiser driveline...

 

[flyer4ever]

Re: OMC SEI Conversion

My cobra runs great, I quess I'll leave it alone for now. I'ts lasted sence 86 so I may have another year or two before I need to worry. Still curious about what they do for a modification to a Gen 2 drive. Ernie

 

[shep247]

Re: OMC SEI Conversion

I guess its about time for an update. Holiday season keeps me pretty busy. I ordered the conversion kit and sterndrive. Everything came from SEI in better than expected time. I called and asked them what gear ratio I should get. I don't know what ratio my old drive was, but it was on an OMC 4.3 ltr. The book says its 150 h.p. at the prop. They recommended I get the 1.81 ratio, and I will probably need to reprop no matter what ratio I get. I took their word for it, as they're who I'll be calling if its not right.

Yesterday I got around to installing the conversion bell housing. It went pretty smooth. I was very meticulous about it, had to run to the shop for grease and bellow adhesive, and got it all done in about 7 hours. (I'm a rookie, and was doing this alone cramped in the back corner of my garage, as I didn't want to re-attach the trailer tongue and drag the boat out.) Someone with more experience could have probably pulled this off in about 2 or 3 tops.

Before I proceed to attaching the sterndrive to the new bell housing I do have a question. SEI didn't put n exhaust bellow in the kit. I looked at my old exhaust bellow, and there were holes along the whole bottom of the bellow. It looked so uniform, I assumed it was like this from factory. There is an optional step of cutting the old bellow to fit the new drive that I can do, but if the old one has holes, I guess I just don't see the point. Can someone explain this to me? How would attaching the old bellows benefit me? Is it worth it?

Thanks guys!

 

[Don S]

Re: OMC SEI Conversion

The OMC bellows had the bottom of the bellows ground off like they put it on a table saw and cut it. All they are, are drain holes. With the drive down most of the exhaust goes out the drive anyway.
Yes, you will need a Mercruiser prop for a Mercruiser drive.

 

[Fishermark]

Re: OMC SEI Conversion

I guess its about time for an update.

Thanks for the update. When you are completely done, be sure to let us know how it works!

 

[shep247]

Re: OMC SEI Conversion

With the drive down most of the exhaust goes out the drive anyway.

Do you mean with the OMC drive or the New Mercruiser drive without the bellows?

Would it be worth it to attach them on the new drive?