Mercruiser vs Volvo Penta

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Following on from my recent questions over single diesel S28 etc. A number of S28 have a Mercruiser 250hp which I guess was fitted because it being more power than the KAD42/43 230hp.

I know nothing about the KAD or the Merc, so to my point:

Which engine is best or are they both just as good, is one more reliable than the other. Who is Mercuiser what block is it based on.

I only have experience of the AD31 which has been served me well.

Thanks again.
 
Sealine is now a part of the same group as mercruiser so a pressure exists to fit the latter.

Look at boats fitted with either Mercruiser or Volvo Penta and generally VP sell for a better price second hand.

VP also have a better dealer net work.
 
The volvo is no doubt the better unit, but less reliable in its KAD form, the volvo 41 series is a purpose built marine unit and has never been used in any other application, so it was designed for the job intended.

The Mercruiser is and Italian based industrial and automotive unit made by VM, they are ok but not as good as the volvo though more popular in the us, massive range of engines all british builders have fitted them over the years offered as options to volvo, the d tronic engine is the 220 4.2 litre unit with electronic management fuel system.

Out of interest I have 2 secondhand 220 with gearboxes circa 1000 hours if anyone needs them, dash, gauges , looms etc.
 
I have owned the Volvo AQAD41 and had a lot of experience with the 42/43 range that followed it, it is basically the same.

Dependable yes but old hat in that smoke and soot is an issue and will cause hours of cleaning soot from your stern and tender.

The VM engine was the first of a new bread of lean burn engines.

The mercuiser 4.2 L was years ahead of anything else at the time, if mercruiser had got the reliability right 15 years ago then Volvo would not still be here, I believe Volvo have only just after 15 years caught up with the D3, D4 series and are also experiencing teething issues that mercruiser have now sorted.
This is in respect of smoke and smooth power.


The better engine to live with is the Cummins-mercruiser, it has hydraulic self adjusting valves, the volvo 41, 42,43 have tappets that may or may not be adjusted on a service, the 42 especially will go pop if the service engineer finds it too much trouble to adjust all the tappets.

If I had the choice between a Volvo D4 and a mercruiser 4.2L I would be hard pushed to choose.....the mercruiser should be more reliable but the Volvo will command a better residual value.

If I had my choice between the Volvo 41, 42, 43 and the mercruiser 4.2L there is no contest....it is like comparing a good old reliable mini and a new mini !

Just start the two up side by side and look at the stern of any Volvo boat after 100nm.........(D3,D4 excepted)
 
I also had the Merc 220's on my BMB and they were great. Servicing cost is exactly the same. The volvo Kads are quieter but an equivalent is 3.6 litres instead of 4.2 so the Volvo is working a little harder.

One inportant feature is that there is a remote oil reservoir for the Mercruiser outdrive which means you can check the oil level without lifting the boat out! A forumite here blew up a Volvo drive by not being aware of a low level.

My choice would be the overall boat not the engines, they are too similar to worry. If ALL else were equal, I'd choose the Mercs.

Mind you I'd bow to the experience of the people on here that actually fix 'em. /forums/images/graemlins/blush.gif
 
Theoretically impossible as the mercruiser is based on the lean burn VM engine.

This lean burn design (2.6 L engine ) was the first diesel engine to power a diesel car that felt like a petrol car to drive.


I think the problem when speaking to inexperienced boater about fuel consumption is the problem that few make passages of 200nm or more so a passage of 25 nm can include 15 miles of slow 7 knots harbour which will distort the mpg.


Lean burn means it has a fraction of the usual amount of fuel injected into it !
 
Yawn, /forums/images/graemlins/wink.gif

Just in case anyone wanted to know how Mercruisers 4.2L is so smooth and can rev to 4000 rpm

The block is built entirely from cast iron, in which a tunnel for the crankshaft is left open. The usual main bearing caps that support the crankshaft are integrated in the engine block.
In the direction of the sump the engine has barriers in between each cylinder. Through these barriers runs one single tunnel in which the crankshaft is built in. The crankshaft in its turn is supported by five strong aluminium main bearings. These bearings are in no way connected to the tunnel. With the engine running the expansion of the aluminium being three times greater than that of steel presses the bearing tightly to the block. And that's not all that happens. The thick layer of aluminium between the crankshaft and the iron block is a perfect 'sandwich panel' to reduce engine vibrations and noise. The barriers mentioned earlier run into the oil in the sump muffle vibrations effectively and add greatly to the stiffness of the block.

The cylinder heads are made of aluminium and are fully separated. They are absolutely identical and interchangeable pieces. This makes them harder to produce but is a key factor in making a strong reliable engine.
The greatest problems with this engine had been deformation of the cylinder heads and their seals so to attach the heads to the block the way of greatest freedom was chosen: every single cylinder head can expand in every direction, without raising pressure on the cylinder block and expand separately from the other cylinder heads.
The result being a diesel engine that will pass any heat/stress test without problems. It should be noted here that during heating up the difference in expansion between a single cylinder head and the head of the cylinder block exceeds 1 millimetre!



Designed for a turbo.

When the use of a turbo is already taken in to account in the early stages of the engine design there will be no limitations in performance. Any limitation will be merely caused by cost issues. If on a lean burn engine performance is pushed with a turbo this will lead to a mixture getting leaner with about 10-15%.
 
Weren't these straight six engines also, that would also account for the smooth running whereas the volvo's are straight fours??
 
I think the 31 was a 4 pot ?

The volvo 41, 42 and 43 have 6 pots as does the mercruiser 4.2L.


Having run the Volvo 41 for 5/6 years and having owned the Mercruiser 4.2L for 3 years the difference between the two is remarkable

If you imagine the Volvo 41 as an old sherpa van and then the Mercruiser 4.2L as a new Mercedes C220 diesel car , that is the sort of difference you can expect !

Volvos new D4 engines are completely different to the old 41,42,43 and are more comparable but still know how to smoke and shake under stress.
 
Hmm that is interesting, the boat I have now has a D4 260hp and it was avaialable with the Merc 4.2 and despite the marketing hype about the D4s i really am not impressed with just how noisy and rough the thing always sounds. I know this is a four pot but it is hyped as a quiet and smooth engine but I am not that impressed with it. It performs well though.
 
I have to disagree with the idea that the mercs are smoother than the Kads. I've been on a windy with 250 mercs and they are noticeably harsher than my Kad 43's. Even the owner of the windy has remarked how much quieter and smoother my kads are? Maybe it's down to my boat being better made than a windy... /forums/images/graemlins/grin.gif
 
Could be down to engine insulation ?

Smooth is holding your boat on the hump without vibration and clouds of smoke.

Clean is after the season I rinse salt water off my tender and there is no evidence of black soot on the white, even brand new Volvos soot tenders.

After you have cruised 100/200nm with your friend who has the jiff out on the stern ?
 
Sorry to disagree again but my dinghy hangs right off the back of my boat and I don't get any soot. I guess the difference may be mine are on legs (kad's not kamd's) with the exhaust under the water?
I will agree that they smoke a little when first started but after only a couple of minutes they are almost smoke free. They realy are.
720 hours relatively trouble free. Doh!! I shouldn't have said that.....
 
Volvo engines have kept me safe in some awful seas and I have often thanked the reliability of Volvos with a lump in my throat, usually as I am half way up a big wave..........

I would not hesitate in buying a boat with volvos in, they are marvellous engines.

The question I thought I was answering was a direct comparison between two engines that I have a great deal of experience with and in particular if someone should avoid a boat with a mercruiser 4.2L engine in.

As I have a pair of these year 2004 Cummin-Mercruiser 4.2 L D300s I thought I would give my response, after owning and covering 14000nm with 41s and 42s and moving on to 4.2L I found a stunning difference and find the Mercruiser a pleasure to own.

I notice Brand new volvo boats returning from a holiday of 200nm to 300nm and they have more soot on thier sterns than I have after a full season.

I helmed a boat with twin D4s last weekend and I was impressed with low smoke at start up and zippy performance, when I held it on the hump there was a shudder and black smoke plentiful.

That said I would not hesitate to buy a boat with Volvos, if three were identical side by side 41/42/43 , D4 and 4.2 L

The 41/42/43 would be ruled out as the D4 and 4.2L are far superior

Leaving the D4 and the 4.2 L /forums/images/graemlins/confused.gif

The mercruiser is im my opinion the better engine but I would probably buy the D4 just for the reason that you and other Volvo die hards will remain non believers and continue to bury your heads in the sand/smoke /forums/images/graemlins/wink.gif /forums/images/graemlins/wink.gif
 
Mercruiser have a bad press.
The engines are smooth and powerful. You can get a 200hp version of the 4.2 (instead of the 220) which is rated for commecial use and bulletproof. I've no experience of the 250 (Efi) version.
The old 180 is a 3.6 version. This is the VM version which they used in range rovers for a while, and it was sold as a BMW marine engine before being badged Mercruiser. It had separate little cylinder heads and I don't think this engine was as good, I had one only for a short while and it was nice and smooth too.
Spares are harder to buy in the UK but very easy to buy on the net from the states, so they are therefore cheaper and easier to come by than Volvo spares.
Engineers are harder to find, but I do my own maintenance anyway.
When you get stuck you go to Andy Judge on Hayling Island who is a brilliant engineer, offers loads of advice and is very fair with his pricing. He knows everything there is to know about mercruisers and you can trust him.
The bad press make Merc boats harder to sell therefore better value to buy if you intend to keep the boat.
If resale wasn't an issue i'd buy merc without hesitation, but for my next boat I just don't know.
 
[ QUOTE ]
Kev b the engine is an italian based vm motori unit, not a jap toyota block.

[/ QUOTE ]


Ah, it'll be the Yanmar that's based on the Landcruiser then?
 
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