Repower OMC stern Cobra to diesel?

[digitalman]

If when I am finished restoring this 25' trophy convertible I want to repower with a used diesel stern drive is this possible? Transom patterns? Know the obvious such as flushing tank etc. Adding electric for glowplugs etc. Just wonder if its possible, has anyone done it, what stern unit(s) would work and where to locate one. I know OMC had a diesel in 1992, Mercruiser had a diesel. I am looking for economy, not speed.

Currently had a OMC cobra w/chevy 350. 4 barrel holly carb etc.

 

[digitalman]

Re: Repower OMC stern Cobra to diesel?

Anyone married a diesel 350 DX Goodwrench diesel to the cobra? Those came out of 82-85 Olds/Buicks etc and if replaced with a DX engine have the durability that the original diesel 350s didnt. Figure it should work as the engines share same 350 block (if you recall GM used the 350 gas block w/o beefing up bearings and led to major failures..and then had to replace with the DX that has the strong main // rod bearings.

Just a thought.

 

[tommays]

Re: Repower OMC stern Cobra to diesel?

A marine diesel requires DEEP pockets ,water cooled tubro ect

They generaly use a different sterndrive with a gear ratio that will work with the diesel power band


Tommays

 

[RubberFrog]

Re: Repower OMC stern Cobra to diesel?

Fuel savings? You mean like spend $10k on the repower to save $1500 in fuel? And you want to do this on an OMC? Sheer madness....

 

[Don S]

Re: Repower OMC stern Cobra to diesel?

Sheer madness....

LOL

Better own a machine shop and know how to build couplers.
The only Cobra with a gear ratio even close is the very lightweight 3.0L drive, and it isn't strong enough for a V6 gas even.
Then hooking up the shift interrupt switch that interrups the ignition would be fun to see.

I know OMC had a diesel in 1992

Never heard that before, but if that was on the cone clutch drive, you wouldn't need the shift interrupt.

 

[HT32BSX115]

Re: Repower OMC stern Cobra to diesel?

The main problems with the Olds/GM diesels was not really the lower end. It was pretty strong. Their main problems were not enough headbolts(blown head gaskets) no fuel filter/separator (!!!) and a pretty crummy injection pump (Stanadyne Which is better now...) And of course NO turbocharger (=NO POWER)

If you want an engine that maybe would be "OK" you'd want either a 6.2L or a 6.5L "current crop" engine.

These are pretty good I gear BUT, (and I like big buts...) BRING LOTS OF MONEY!


All things being equal etc.......I would NOT bolt ANY diesel to a Cobra.

It might do ok bolted up to my 1.43:1 King Cobra outdrive (for sale btw!) since that drive was connected to a 460 and survived.... but you'd need to put a pretty "tall" prop on it since the diesel would want to turn only about 3600 at WOT. For fuel economy you'd want to cruise it under 2000 rpm.


at that RPM you probably would be breathing a lot of diesel smoke in a light tailwind!




Regards,



Rick





Also as Don indicated, unless you use a Cobra with a cone clutch, once you got into gear, you'd eventually break the shift cable forcing it out of gear(or you'd have to shut it off every time you wanted to come out of gear)

It's pretty hard to interrupt a diesel......Oh you could probably pulse the shut-down solenoid on the injection pump....until it failed....

Anyone married a diesel 350 DX Goodwrench diesel to the cobra? Those came out of 82-85 Olds/Buicks etc and if replaced with a DX engine have the durability that the original diesel 350s didnt. Figure it should work as the engines share same 350 block (if you recall GM used the 350 gas block w/o beefing up bearings and led to major failures..and then had to replace with the DX that has the strong main // rod bearings.

Just a thought.

 

[whywhyzed]

Re: Repower OMC stern Cobra to diesel?

We have one of those OMC Cobra diesel rigs at the school all mounted on a stand with gauges and such that the students made up for it. It has a Cobra drive, I forget if it has the bump or not. I also forget who made the engine - some Scandanavian company or something. Sweet looking package. I think it's 250HP... I remember noticing that it's turbo'd and intercooled.
Of course like most of the goodies the marine guys have - it has zero hours.
meet me at the school some night around midnight with a fist full of big unmarked bills.. hahaha

EDIT: It was 200HP electronic diesel FDE 236 made by Austrian company called Steyr and it looks like you can d/l a service manual for it here:
http://www.steyr-motors.com/technical/t_part_marine.htm
Cool site they have

 

[whywhyzed]

Re: Repower OMC stern Cobra to diesel?

Here's a pair of Cobra diesel drives in Europe.
With transom assemblies!

http://www.marinepowerservice.com/Classifieds/AdView.cfm/adID/500/classCatNEW/26.cfm

 

[digitalman]

Re: Repower OMC stern Cobra to diesel?

Thanks for input. I was really interested not only marrying a diesel to cobra..what about just diesel conversion..ie outdrive and engine together,,such as penta or similar? Just wondering the options. I mean it doesnt make sense to put another OMC in it if the whole thing has to go. Mercruiser? Mercruiser diesel (there was one).

Think I will nurse the OMC alone and look for a diesel inboard or Sea Ray with twin 4 cyl diesel drives. (30 footer)

 

[digitalman]

Re: Repower OMC stern Cobra to diesel?

OK lets get specific. If I wanted to pull the OMC cobra completely out..stern drive and engine..ie bare hull.. could I retrofit a volva stern/diesel combo to the boat? Some reseacrh has shown the A031 engines / stern drives to be good and have reasonable parts availability.

How does that sound and would it work? 25' trophy 9.5' beam 6500 displace
current is 5.7 liter gm with cobra outdrive.

 

[Richierichie420]

Hey, I’m trying to get the same engines for my 45 foot grand mariner. Are they worth it seeing that omc went out of business 20 years ago I’m wondering about parts and how easy they are to get