Mercruiser 7.3 D Tronic Replacement/Swap

[SJHE]

I am looking to replace the very tired and forever unreliable Mercruiser 7.3l diesel that is in my powerboat. Sadly, my budget does not stretch to a new Yanmar or Cummins equivalent so I am on the lookout for a good used replacement engine... Does anybody happen to know if there are any other Mercuiser diesels that will drop straight onto the existing engines mounts? I currently have a Bravo 3 duoprop outdrive and would like to utilise as many of the current installations components as possible.
Thanks in advance.

 

[spannerman]

The 320 D- tronic may well fit, its a straight 6 so may be a bit longer than your V8 lump, but its about half the weight and has more HP.
The engine mounts may fit as they are adjustable for width IIRC, but not sure where they sit for/aft in relation to where they are at present. It will fit straight onto your transom shield but you'd have to fine out what gear ratio your drive has to see if it would be compatible as the 320 spins a bit faster than the V8.
Those old International Harvester V8's were only any good as anchors!

 

[SJHE]

Thanks for your advice - will keep my eyes peeled for a straight 6 Mercruiser. If anybody hears of a good one for sale, I'd be much obliged if they could let me know...

 

[burgundyben]

If your handy with the spanners you could buy an ex vehicle Cummins B series and marinise it with the Bowman manifold and heat exchanger.

 

[dieselboy]

ask latestarter on here if he has a couple of suitable units...if he doesnt, he probably will know someone who does!

 

[Latestarter1]

ask latestarter on here if he has a couple of suitable units...if he doesnt, he probably will know someone who does!

Love to help, however torque of Cummins 6B Series turns gears in Bravo 3 to mincemeat in short order.

Yanmar 6LP will work, just.

 

[SJHE]

Thanks for the suggestions. Is there a sterndrive out there that can cope with the Cummins torque? I know that Konrad make some pretty heavy duty units but never seen one up for sale on the second hand market!

 

[Latestarter1]

Thanks for the suggestions. Is there a sterndrive out there that can cope with the Cummins torque? I know that Konrad make some pretty heavy duty units but never seen one up for sale on the second hand market!

SternPower are good units and plenty about as they were used on M.O.D Pacific RIBs however their strength is their underlying weakness, gear shifting is by external Velvet Drive 72C 1:1 transmission, good gearbox but runs out of capability around 250 horsepower, can be coaxed a little further, however 300 is a bridge too far,

 

[SJHE]

Thanks for the suggestion. I had considered the Sternpowr but unfortunately there is not enough space in the engine bay for such a long drive train. If I can find an alternative, can anybody recommend a good engineer in S W Wales that may be able to help with installation?