How good those diesel engine marinized from car?

[taobsu]

I have seen quite a lot car engines has been convert for marine purpose.
Two relative new brand are: VW diesel and Marine Diesel (use Hummve diesel). I am wonder how they fare with other established brand in terms of duty cycle, weight power ratio,and price? For those two mentioned above, the HP top around 300HP. There are talks about use them as gas engine's repower option, due to their size and power range.

My question is, other than limitation power, are they worth to consider as designed-engine instead of replacement unit?

[StianM]

Manny engines are bolted to the hull without rubber betwen so the engine become stressed and I'm not shure how good car engines is in this case.

We have used some tractor engines and that woek well, but on a tractor the engine is a part off suporting structure.

[FAST FRED]

The usual problem is the automotive Hp rating has nothing to do with the ability of the engine in a boat.

The VW may be car rated at 60 hp but in a boat more than 25hp or so 24/7 will cause reliability hassles.

Some "marine engines" that come from light duty sources (Volvo) do not have any ratings BUT pleasure boat , 100 hours a year , 10 years expected life.

The style of boat and operation will detirmine if the engine swop is worth the effort.

For a water ski boat or brown water fun boat . why not?
Ina working trawler an auto engine might be iffy , although many truck engines WILL work just fine at rational RPM's .

FAST FRED

[mattosmond]

i have heard that some current maine diesel engines run at the redline limit most of the time, whereas car engines only touch the redline for short periods of time. surely this is a reason why on the whole marine leisue boats have some problems with reliability, especially when an automotiv engine has been used...

[fcfc]

You have to trust the builder/seller of the engine. It is very hard to know what is inside.

For VW, for the 1.9L block (I know it is lower power than what you need). VW has sold cars with variations upon this block from 60 hp to 170 hp, depending on models and countries of export, plus racing versions up to 210 hp.( as far as I know)

So when someone wants to sell you a marine engine based on a VW 1.9 block, sold for 80 hp, what is the crank inside ? cast iron from the 60 hp version ? the forged ultra high steel, hardened, nitrited, cemented from the 210 hp version. Or any intermediate version ?
Even if you had the engine open in front of you, you could not tell unless you had access to a metallurgist laboratory.
And even if you find it is the same alloy, same heat treatment. Is it the same manufacturing tolerances, same balancing ? Again, you do not know.

It is the same for every mechanical part inside. You are bound to trust the engine seller.

So, if garage joe says take a 80 hp VW wreck engine, buy my marinisation kit (mainly combo exhaust/cooler/exchanger/expansion tank + sea water pump), you will have a 80 hp marine engine, you may doubt.
When VW marine, subsidiary of VW, says we sell 80 hp marine engine from VW blocks, they have the ability to use any sligth (if we can say ) variations in parts, such as additional heat treatment, different alloy, additionnal machining, different cam timing, etc ... and at end have a true reliable 80 hp engine.

[FAST FRED]

i have heard that some current maine diesel engines run at the redline limit most of the time,

The GENUINE boat motors of say 300hp+ will frequently be used at a really good percentage of their ability.

Redline , almost never , but 80% of rated hp at 90% of rated rpm works for many thousands of hours .

Auto takeouts are fine IF their realistically loaded. The perkins 4-108 is an ex auto engine , that does really well in many sailboats , but they usually load them under 1gph , or about 16 hp to get 5000 hours.Much more than 25 cont hp spells a shorter service life .

FAST FRED

[lonestarcruiser]

Forged vs Cast Crank Identification
Take a file and hit one of the counterweights a few strokes with the edge of the file. If it cuts, its cast, if it doesnt its probably forged.
Lonestarcruiser

[burt2]

Auto motive diesels have a very easy life once a vehicle has reached its desired speed you can throttle back and barely use 25% of its HP, planning boats are like driving your car up hill its hole life although the amount of HP that is required to keep them on the plan is less than to amount needed to get them on you don’t throttle back any near as you do in a car if your lucky you will be planning at 70% throttle.

No offence to Americans but there Famous V8’s are quite cheaply made poor steel quality they rely on big displacement = HP, your lucky to get a 1000 hours out of a Petrol V8 before a complete rebuild most are around 600 hours and I fear Marine Diesel wont do much better. American auto engine manufacturing is almost advanced as Japan was in the 80’s new technology seems very slow to emerge in the states.

On the other hand marine diesels like cumins are very good and quite up to date in fuel advancements and electronic controls.

[FAST FRED]

"your lucky to get a 1000 hours out of a Petrol V8 before a complete rebuild "

This is no problem with most boat owners.

Few get to do 100 hours a year , and most have sold the boat before a decade is out.
The power density of the gas engine allows quick plaining and little intrusion in the boat , there also smooth and can be muffled to be really quiet.

Many of these marinized gas engines are used in the Great Lakes and other fresh water cruising grounds , where they don't even bother with heat exchangers .

As a new factory crate engine can be had for under $2000, simply swoping the "marinization" gear gets another 10 or 15 years of summer toy.

Not what one would need for a trip around the world , but they work just FINE for their owners.

FAST FRED

[Vikendios]

I think Fast Fred is right. The problem is that in New Zealand, as in Scotland and Greece which are my usual playgrounds, you face an entirely different kind of environment that most Americans face. Americans are blessed (or not ?) with a lot of protected inland waters, marinas, cheap fuel, well organised repair services, up to the minute weather forecast, and Coast Guard help, and 90 % of their boating public won't stray much from these facilities.

In the Eastern Med and Scotland (once away from the major towns) we have none of the above. We have what I consider to be the best cruising grounds in the World, but we have instant gales. lousy anchorages and very little outside help. We also have five or six weeks of vacations every year so we use our boats more, and on longer trips.

Every North European sailor who goes to the Med will have to cross the notorious Bay of Biscay, and thousands do so every year. So we have to use oversized all-chain ground tackle, extra heavy boat construction, and super reliable but efficient (fuel cost is huge) diesel engines. And my boat doesn't know what a slip in a marina is.

This is why I think a lot of the advice you will get on this site is not suited to European or New Zealand boating. But I envy the Americans because their boating is much cheaper (all things equally considered) and therefore accessible to a lot more people. And that's wonderful.

Vikendios

[burt2]

yes america is a differant kettle of fish New Zealanders use there boats alot and are very hard on there gear we have a little alloy boat with an evenrude outboard wihich has clocked 3500 hours been rebuilt once though. So i admit there cheap HP and preform very well its only the relyability i care about and if you only do 100 hours a year i supose you would get 5 years of use before it gives trouble.

Like Vikendois, in new zealand we do alot of long trips i think we would do around
200 hrs a year this would gives us only 2 or 3 years witout trouble after 500 hours these engines are getting tired.