Engine swap?

I have a 1988 24ft Bayliner trophy with a 5.7l omc/cobra outdrive, has anyone repowered one of these with a diesel equivalent ? if so what did you use or does anyone know what would fit in engine bay
Current engine runs fine, its just the cost of petrol over here in UK (£1.40 per litre) and i have access to very cheap red diesel
Dont want to put in a new engine/drive as this wouldnt be worthwhile economically, just want some advice as to what would be a good used replacement
Thanks in advance for any advice, Nick

anyone got any ideas?

welshswampy said:

anyone got any ideas?

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Yes.... forgo the idea of a diesel swap!
You'll never realize a decent return, IMO.
Since you have the Cobra drive, this leaves you open to a Volvo Penta DP-S conversion.
Many in the US have done this!
While this may still be expensive, it will be less than if you were to do the diesel conversion.

The DP-S will normally render a performance gain in the area of 25% or so.
A kit is necessary, and the correct over-all gear ratio for your 5.7L engine.... of which should be 1.95:1.
This leaves you with a Cobra that could be sold.

Food for Thought!

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Thanks for reply Rick, I'm not too concerned about a decent return as the boat was very cheap in the first place, I would like to swap over as the price of fuel over here is ridiculous and getting dearer! and I have access to very cheap red diesel

There are no Borg Warner components that will aid in a Diesel to OMC Cobra drive system conversion.
This would include the using the DP-S drive conversion.
Plus, the OMC Cobra will likely not handle the diesel torque.

The additional weight of the diesel engine will also sacrifice performance in that it will make this hull somewhat stern heavy..... the Duo Prop drive will help with stern lift.

Most diesels that can be marinized, are Borg Warner capable.
If you do the diesel, you may as well also go to an AQ series Volvo Penta Duo Prop (not the DP-S style).
The Borg Warner pattern F/C and a V/P PDS adapter housing can take this to an AQ series V/P Duo Prop drive..... of which is a better drive anyway, IMO.


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OMC actually made a 200HP 6 cylinder diesel/Cobra combo - the engine was Steyr but was branded OMC

I know where there is an almost new one in N.America for around $15,000 US - plug and play

would be a useless swap though. even if you had free diesel, you'd probably never see a financial benefit.
If you aren't looking for "return" as Rick suggested, then why do it? you like the nauseating smell? prestige? like to brag of expensive maintenance costs? (a set of 6 Steyr injectors is over $2000 remanufactured)

Your fuel is cheap. Gas in the UK used to be 2.5 the Canadian price. It's $1.46 per liter at my local marina today for 87 octane.

I wouldnt pay anything like 15k!!!
My question was, has anyone repowered with a good used diesel
I was thinking something around the few grand mark, I dont pull any skiers, its just for fishing
The drop in performance wouldnt bother me
The boat is only worth a few grand
Ive seen a GM 6.5l diesel with 280 sterndrive including transom etc for £2800 or best offer, the engine has been reconditioned but no info on the leg,this was the sort of figure i had in mind
Would this GM lump be physically too big/heavy