Old Volvo vers New Cummins Mercruiser Shaft Drive Diesel

[DAKA]

I am looking to change my Corniche and I thought I had found a perfect boat but it has been re engined with a 2004 4.2L Cummins Mercruiser 300 HP shaft drive diesel

I have been told that this is more Mercruiser than Cummins and it started life as a BMW.
Is this correct?

I know Mercruiser stern drives have just taken a battering and I would like to know what engine will give the best service and resale value as I have a choice of two boats.
The boats are similar in all other respects including cost.

Choice of 1996 Volvo 63L 318 HP
or 2004 Cum/Merc 300 HP
Although this is a 2004 engine it is already an obsolete modle which does not help my confidence. /forums/images/graemlins/confused.gif

 

[[2068]]

Fairly sure the Mercruiser engine was never a BMW, more likely a VM Motori Italian block, marinised by CMD. Advantages over the 6.3L Volvo include reduced weight/size/fuel consumption. Comparing to a much older engine isn't easy, it all depends on condition/maintenance: personally, I would choose the newer Mercruiser, unless the Volvo was in really good nick.

dv.

 

[tamarind]

I would prefer the Volvo's only if in good condition. Better resale value, also spares will be easier to get hold of, a tried and tested motors!

 

[mercman]

BMW were the first to use this engine and after a few years Mercruiser bought out BMW marine. They ran the engine in the same guise for a good few years. Little has changed different intercoolers, heat exchangers, turbo`s, hp ratings and litre sizes.
Yes it is a VM and MTU use the 6 cylinder in exactly the same form on their smaller range. VM is part of Detroit they bought it out a few years ago.
The 300hp i wouldnt say is discontinued it is now 320hp. Slighty different dual stage injectors, different cylinder heads.
Parts are not going to be a problem.
Gearboxes have had a few issues get them checked over by a dealer. If in doubt get me the engine numbers i can look into the warranty history for you....see if there was any major issues with them

 

[omega2]

My mate had brand new mercruiser 180, VMC, which after 2 years devloped an oil leak in the timing case area, when investigated it was found that the sump is made from mild steel, although he was able to aquire an alloy one to replace it. The original sump had corroded away, and it was a gasketless fitting.

 

[oldgit]

Perhaps for any marine operation the heavy but lightly stressed and well proven lump would be best..Be interesting to compare the RPM of both units.

 

[kimhollamby]

The original 300hp Mercruiser diesel...

...was based on the old Navistar V8 diesel and didn't feature in the BMW range. It has been dropped from the CMD range because it cannot meet the new emission standards and power-to-weight ratio increasingly out of step.

It is the 5cyl and 6cyl inline Mercruiser/CMD diesels that were/are based on VM base blocks and originally featured as BMWs. The original BMW versions suffered cooling problems, the early Mercruiser ones still weren't completely sorted but there's been a few years of development since then. The 5cyl is no longer featured.

The one you are looking at sounds like a 6cyl 4.2lt of relatively recent vintage - the latest version offers up to 320hp at the crank.

 

[mercman]

Re: The original 300hp Mercruiser diesel...

sorry Kim the 270hp V8 was a Navistar the 300 was actually a Ford. Another reason it was dropped was it was a complete pile of s**t.
The 6 cylinder VM engines used to suffer a lot with rear crank seal probs.....the new ones were the crank pullies falling off and the key way machines out the taper in the pulley. They have now fitted left hand threads to combat the nut winding off. The 7.3 V8 was also dropped a couple of years before CMD took over the diesel side