gas to diesel

[lilmandavis]

would an omc cobra that was geared for a big block be able to be convereted to diesel? it never runs over 4000 rpms and i dont see any diesels that go over that either? im ready to switch over and dont want to buy an outdrive umless i have to ya know.

 

[Bondo]

Re: gas to diesel

Do you have a Particular Diesel in mind....???????......

 

[Don S]

Re: gas to diesel

The gear ratio isn't right for most diesels because of the rpm. Plus the torque. Not sure you can even find an OMC prop that would do the job.<br />The other problem with those drives is the lack of parts for the big block outdrives.<br />Then you get into flywheel housings that fill adapt the motor mounts on the aft like OMC does.<br />Then, you have the exhaust to deal with. Where are you going to find part to go thru the drive. I don't think you are going to want thru transom exhaust with a diesel.<br />What kind of diesel were you looking at installing?

 

[lilmandavis]

Re: gas to diesel

one that fits the shaft comming out of the cobra lol!!! any suggestions of what kind?

 

[lilmandavis]

Re: gas to diesel

i am a machine fabricator by trade i can get the exaust to work and as for cast iron i can tig that, so the motor mounts will need to be worked with but, as for big block parts ive got a whole big box full of gears and bearings. all brand new for the big engines i actully have two complete sets of new upper and lower gears and bearings to redo that particular lower end but im just sick of gas big blocks. what kind of prop would i need? last trip out i lost more hair from pulling it out

 

[Bondo]

Re: gas to diesel

I don't know if they Still Do,... But Merc. has used the 7.3l Ford/ Navistar motor.........<br /><br />That,+ a Bravo III is My Personal Dream Driveline...........

 

[Don S]

Re: gas to diesel

Oh yea, forgot to mention, you will have to find a coupler that will fit the bolt pattern on the diesel crankshaft and fit the splnes of the shaft.<br />Those rear mounts have to put the CenterLine of the crank in direct line through the CL of the gimbal bearing.<br />A good CAD drawing of the diesel of choice and some time with a good CAD program and it's possible. Still, you have the wrong gear ratio and OMC never used diesels with Cobra drives.

 

[lilmandavis]

Re: gas to diesel

hmmmm well my fiance is a cad specialist so im good there !! what set of gears should i look for. i could machine a adapter plate for a coupler i guess. what did this navistar come in are they new, old, not ten thousand dollars? is it possible is what im saying. and i guess what do i need to get is what im asking. as for gears?

 

[lilmandavis]

Re: gas to diesel

would the cobra hold up? im not a wide open kinda guy- im a cruiser..im thinkin of safty and reliability. and its efficient...diesel anyway

 

[Don S]

Re: gas to diesel

If you want reliability, loose the Cobra.<br />There are no "Correct" gear sets for Cobra's because they were never used with a diesel. <br />You then run into a problem with a shift interrupt system so you can get them out of gear. Merc uses some small diesels that shake bad enough to not need them, not sure with what ever you plan on using.<br />I just think you are making a big mistake trying to put a diesel on a drive that hasn't been built for 10 years and the company that produces parts went out of buisness 10 years ago. That alone would kill the reliabilty issue for me.

 

[lilmandavis]

Re: gas to diesel

http://www.sterndrive.info/index.html <br />heres the cobra owners heaven lol

 

[lilmandavis]

Re: gas to diesel

is there a drive that would cover the holes in the transome? without having to blow the whole thing out?

 

[Don S]

Re: gas to diesel

The Mercruiser Bravo drives (all Bravo drives) all Volvo SX/DP-S style drives use the exact same transom cutout as the OMC Cobra.

 

[Bondo]

Re: gas to diesel

Originally posted by Don S:<br /> The Mercruiser Bravo drives (all Bravo drives) all Volvo SX/DP-S style drives use the exact same transom cutout as the OMC Cobra.

Would this mean that the Alpha Gen.II will Also bolt right Up,..??.. It matches the Bravo.....<br /><br />And,... The Alpha 1,+ Pre Alphas would bolt up,+ have a couple of Extra Bolt Holes,.....?????.....

 

[Don S]

Re: gas to diesel

Matter of fact, you can get a kit from Volvo that will adapt the SX/DP-S drives to the OMC transom shield. That drive would be much better behind a diesel than the old Cobras, but even Volvo doesn't use them on any of their diesels. Bravo's are being used on Yanmars, the 7.3 Navistar, and those nasty BMW diesels. <br />You would be better to look at a complete repower setup as using a piece by piece from everywhere. The way you are going with this you will have something that is impossible to sell down the road. With no way for someone else to get a broken part or help to fix it.

 

[Don S]

Re: gas to diesel

Bondo, yes the Alpha's also take the same cutout. But I wouldn't stick an Alpha on a diesel of any size.<br />So far we haven't heard of what size diesel lilman is looking at or thinking about.

 

[Bondo]

Re: gas to diesel

I Agree Don,.....<br />This is just Future Reference for All Those guys that are getting Sick of the OMC dilemma,...........<br />And, Wanting to Repower their Hulls........<br /><br />Unfortunately,....... There were Many Beautiful Hulls powered by OMC,..........<br />I Know,......<br />I'm Refitting 1 now,+ Helping with Several More...........All Stringer drives through......

 

[lilmandavis]

Re: gas to diesel

probably something thats electronic controlled so i can utilize a shift interupter right? im a ford guy but i really love cats lol but thats not realistic i dont think. its a 30 ft boat. know anyone that wants to buy a 460 ford pushing the best drive ever built---cobra lol? all rebuilt, box full of goodies to go with it

 

[Don S]

Re: gas to diesel

A Cobra won't handle a Cat pushing a 30' boat. It's a wonder it handled the 460. Couldn't imagine the gas that must eat when on plane. <br />I know most people figure miles per gallon, wondering if you are actually using yards per gallon???? Just kidding, Kind of.<br /><br />Bondo, yes the hole is the same for even the older Alphas and yes there are a lot of neat boats. I am right now repowering a 1969 Uniflite 24 ft inboard. Was a 318 Chrysler, will soon be a Volvo D4-210HP diesel with Electronic Vessel Control. talk about culture shock for an old boat. No shift or throttle cables. all computer controlled.

 

[Bondo]

Re: gas to diesel

will soon be a Volvo D4-210HP diesel with Electronic Vessel Control. talk about culture shock for an old boat. No shift or throttle cables. all computer controlled

And All I ever wanted is a Mechanical Injected 7.3l, That I'd Twin the Turbos on,.... With a Bravo III..............<br /><br />I Guess I've got My Sights set alittle Low................