Cruising.Boat Racing Engine. Why?

[Sneds]

I’ve been thinking, since spending, not an inconsiderable amount, last year on a super charger clutch and a new supercharger why do we we need these performance parts on a cruising boat.
On a sleek wave piercing dart I understand, but a boat designed more for accommodation than performance is it really necessary?
Who cares if it takes two seconds, five or ten to get on the plane you are out for a cruise not a drag race and so why do we need these over stressed high performance engines?
The more I think about it the less sense it seems to make

 

[vas]

I guess because you'd need a larger (in displacement and weight) engines in order to get you to the plane. do you have space to accommodate them?
If the answer is yes, then your argument is valid, but I thought that the turbo+supercharger ones are fairly small in size and high in power in order to fit in small circa 30ft engine rooms two up.
I doubt my two relatively relaxed 330hp 6.7lt straight sixes will fit in a 30ft hull.
OTOH, if you want/must have 30+kn cruising on a 30ft boat you wont be able to do that with 2X180hp relatively relaxed diesels.
[all # approximate, gonna hide and wait for the attack...]

 

[Sneds]

My boats is a Sealine F36 Kad44
Part of my point is I would be happy to sacrifice some performance for less stressed easier working engines

 

[pumpsmynads]

Some of those nordhavns have a 90hp diesel and they run forever.

 

[Momac]

The more I think about it the less sense it seems to make

I agree and suspect your boat may go okay without the superchargers since a F36 goes okay with less powerful kamd43's.
Maybe a displacement boat next time ?

As a matter of interest what caused the supercharger to fail?

.

 

[Mr Googler]

Space and speed.

Supercharger is there get the turbo charger spinning further down the Rev range than it otherwise would given its size.

F36 is a full planning 30 knot + boat...designed and sold as such.

Can’t imagine they would have sold as well if they had been a 15 knot boat and would have been designed differently.

If you want to go that speed...better to have a semi displacement etc....

 

[tico]

Kamd44 -supercharger= ad41= 200hpx2= 400hp
F36 will need a bit more than that to get over the hump and on to the plane.

Compare with phantom or princess 38..... twin tamd 63p=720hp
Supercharger great on targa type sports cruisers which need the short burst of power to get over the hump onto the plane. Not so good (imho) for heavier flybridge cruisers which are better suited with larger displacement lumps with more 'grunt'

 

[BruceK]

It's not just about power. It's also about heat transferral. Blowing more air through the engine helps keep it cool. Remember it's diesel not petrol. With the KADs it's a finely balanced system and you cannot remove a component thinking it will de-stress the engine. Quite the reverse. Remember, the coolant system is basically for the block, the pistons are cooled via oil and the pre-cooled charged air.
Also those so called relaxed lumps are actually operating at a higher compression which we compensate for by charged intake and so one could say, those relaxed lumps actually experience higher stresses (*EDIT which is one reason they dont rev as high). Not all is as it first appears.

 

[BruceK]

It's also worth noting what the KAD series was competing against. It's the diesel competitor to the petrol V8. That should tell you all you need to know as to the why's.

 

[rafiki_]

I’ve been thinking, since spending, not an inconsiderable amount, last year on a super charger clutch and a new supercharger why do we we need these performance parts on a cruising boat.
On a sleek wave piercing dart I understand, but a boat designed more for accommodation than performance is it really necessary?
Who cares if it takes two seconds, five or ten to get on the plane you are out for a cruise not a drag race and so why do we need these over stressed high performance engines?
The more I think about it the less sense it seems to make

Volvo we’re going through a transition when your engines were engineered Iain, before the D series were introduced. Nothing wrong with turbos as long as the oil and coolant are regularly serviced. I agree the supercharger are not great on a cruising boat, but I think Volvo were left with a torque hole in the curve before the turbos kicked in and made a difference. The Cats in the Azi are a fair bit larger in displacement than your Volvos, and I guess charged a significant premium over the Volvo price as fitted in Sealines?

 

[rafiki_]

It's not just about power. It's also about heat transferral. Blowing more air through the engine helps keep it cool. Remember it's diesel not petrol. With the KADs it's a finely balanced system and you cannot remove a component thinking it will de-stress the engine. Quite the reverse. Remember, the coolant system is basically for the block, the pistons are cooled via oil and the pre-cooled charged air.
Also those so called relaxed lumps are actually operating at a higher compression which we compensate for by charged intake and so one could say, those relaxed lumps actually experience higher stresses (*EDIT which is one reason they dont rev as high). Not all is as it first appears.

Bruce, the pistons are cooled by excess diesel as well as oil.

 

[BruceK]

deleted.

(I thought the documentation was in the manual but it isn't. However I do have the documentation or article somewhere and when I find it I will post it up.

 

[Portofino]

It's not just about power. It's also about heat transferral. Blowing more air through the engine helps keep it cool. Remember it's diesel not petrol. With the KADs it's a finely balanced system and you cannot remove a component thinking it will de-stress the engine. Quite the reverse. Remember, the coolant system is basically for the block, the pistons are cooled via oil and the pre-cooled charged air.
Also those so called relaxed lumps are actually operating at a higher compression which we compensate for by charged intake and so one could say, those relaxed lumps actually experience higher stresses (*EDIT which is one reason they dont rev as high). Not all is as it first appears.

Hang on Bruce high revs mean higher stress as they need far higher mean piston speeds esp if longer stroked .
Think about it the acceleration and more importantly the deceleration forces to “ lap “ 4 inches at 3400 rpm compare to 7 inches at 1800 rpm .
A quick Google of the compression ratios tends to suggest VP s KAD series pretty high not low as you say .
Its your KADs I would say hold the most stressed trophy compared to none SC .
few examples.

 

[BruceK]

So as not to stall the debate I will continue as I recalled reading it.

Porto, I was not singling out MAN or any other. Rather a traditional lump. So with Volvo if we follow the KAD lineage what we see starting at the MD31 is 18:1 moving to 17.5:1 for the 41 series and ending at 16.9:1 by the time the 44/300 evolved. The 42 interestingly showed a brief spike to the downward trend.

I presume you are all more familiar with the latest trend in diesel technology called LTC (Low Temperature Combustion?) If not it's worth a read. Anyway, the story went along these lines. A better burn was created if there was a premix of air and diesel. Remember we are still before the common rail and massively high injection pressures of a modern diesel. Dropping the compression ration and adding boost not only delivered more power but allowed for a change in valve and injection timings to advance and avoid knock and uneven combustion. In addition a lower compression ratio allowed a cooler compression cycle. What slack there was is taken up by charged air that has been pre-cooled. (inter-cooler CAC) So now you have less heat generated in the cylinder from compression while at the same time forcing in compressed cooled air from the charge sytems via the intercooler cooling the cylinder and piston crown vastly more than negative pressure of a normally aspirated engine. This in turn also went forward into allowing earlier injection and mixing without knocking occuring.
This is where LTC comes in on modern engines too. Because the resultant burn is as it states, lower in temp. Lots and lots or small refinements all balanced and stacked together to make a whole. As I said above, the KAD is a balanced engine. You need all those components. Remove the supercharger and you may induce knock during that transition phase.

 

[Hambleite]

Option Types:

1. TAMD 41 - 3.6 litres, 200hp - might or might not be enough to comfortably get a specific boat on the plane given the fact that getting on the plane needs a lot of torque.
2. Ford/Perkins/CAT/TAMD60/61/63 - typically 6.0 litres - enough torque to get on the plane but much heavier, bigger, more costly
3. TAMD41 with a supercharger (KAD42/43/44/300) - 3.6 litres, 230hp-285hp - lots of torque to get on the plane but without the weight, size and cost of the Ford/Perkins/CAT/TAMD60 variants.............jobs's a good'n!

I can remember a time when a lot of motorboats in the early 1980's basically had engjnes that weren't really powerful enough for the desired application. Think AQD40s (130hp), Perkins (145/175), Ford Sabres (180hp). Think early Princess / Fairline etc. Some of these boats would barely get on the plane and even if they did, a top speed of 20-23 knots seemed ok at the time.

Even a Sealine 305 Statesman with AQAD41s would take ages to get on the plane (short hull, heavy engines in the stern). On a AQAD31 with 150hp, these could also take ages to get on the plane in say an S28 or Targa 29. Adding a supercharger upped the HP to 170hp making the KAD32 but it made a world of difference in the usability of the engine.

 

[[2068]]

The short answer is that "taking some time to get onto the plane" is within a hairs breadth of "never being able to get onto the plane" with a bit of additional load or fouling.

You can compare the supercharged / non-supercharged versions of the current D4 ranges by looking at the sterndrive / inboard versions.

The non-supercharged inboard version has a torque peak that is higher, around 2600rpm.
The supercharged sterndrive version produces more torque at 2000rpm.

 

[QBhoy]

All to do with efficiency progression.
When I think of the sheer size and weight of something like a Tamd61a at 306hp at their highest rating...and the size of the modern equivalent VP producing this and more now. Half the size and weight nearly. Doesn’t mean better, I’d hasten to add ?

 

[Moodysailor]

I worked as a VP mechanic at the time when the KAD 43/44/300 were new, and when the D series was introduced.

When the KAD300 was released, the main driver was the boat manufacturers, driven by the consumer - they all wanted to be able to advertise a higher speed, and [insert name of average customer here] wanted to be able to tell their friends in the bar that they had the fastest boat. Vanity was the means to this end, simple and inevitable.... as there was a demand, VP obliged.

The KAD range was always unapologetically a high power density engine - there wasn't much else to compete with it at the time except for petrol's at the high end and one Yanmar against the KAD32, as some alluded to above. It was never intended to compete directly with the higher displacement, much heavier engines as it was primarily a sport boat engine that gave manufacturers the design freedom they wanted without having to stick a V8 petrol in which a large chunk of the Euro market didn't want to do. IMO, they always worked best as a sterndrive - I was never a huge fan of the KAMD range as the type of boat (with some exceptions) which is designed for an inboard typically didn't need the high torque compressor.

The net effect of the higher power was that in the performance cruiser market (as the boat owned by the OP), the design envelopes were 'stretched' so that these boats were really at the limits of the engine and starting to reach into territory typically the reserve of the higher capacity, larger displacement engines. But the boats were designed with much greater cabin and entertaining space, and sold really well. In short, as as someone else said above - if you reduce the power (specifically, the torque) in a boat like this chances are it won't get on the plane at all. I've seen some examples so marginal that they had to have SS props fitted (on KAD44) and the bottom had to be clean or they simply would not plane - had a lovely cockpit and two large cabins though ;-)

As for the D4/6 series - I remember these words from someone at VP well - "if we could continue to make the same engines and just incrementally improve them, we would - after all they are proven, and make very good profit. But emission legislation changed, and our current range would not have met the targets without significant compromise - so we decided to build something new, and took the opportunity to re-think everything"

 

[kashurst]

I have a pair of KAMD 300s in a 38 foot flybridge (rodman 38) -absolutely brilliant! However the manufacturer has built the boat for reliable performance at the expense of reduced top speed. My boat is about 9 tons at 50% load and tops out at @ 24 knots. I cruise @ 17 -18 kns.
In the med we get loads of fouling very quickly - whatever you use. The Rodman never fails to leap onto the plane and is very confidence inspiring in bigger seas because the power curve is very linear and there is loads of torque from low revs up to near max revs. So if you have to slow down a bit, because of sea state, the boat is always very responsive to the throttles even in the on/off plane zone and eager to accelerate again.

I am comparing this behaviour with other boats I have owned with TAMD 63Ps in. The 63P is a terrific engine except the torque curve changes dramatically from 1400 rpm to 1600rpm. This is typically on or close to the engine speed at which a planing boat starts climbing the hump. I have had a few experiences when the boat was unable to get onto the plane because of med fouling and big waves. As a result having to motor out beam on to the sea (very rolly polly) then turn to run with the wave direction in order to get that extra push and climb over the hump. Then slowly do a 180 turn and go the direction I wanted to. Not nice and alarming for in experienced passengers. The problem with this behaviour is you don't know the boat is going to struggle until it does.
This as other posters have described is so manufacturers can claim the magic 30 knot top max speed. That same boat with different props could have been set up to max out at 28kns and be climbing onto the plane at 1600rpm+ when it would work very well. Unfortunately when you buy a boat you don't get to test out these issues and modding props is not simple or cheap.

I can see why Sneds (OP) is annoyed about the supercharger failing - expensive. (Question do you know why it failed)
However the bigger lazier engines sometimes break too and the bits for them are suitably higher and they cost quite a bit more to service every year. 63P turbos are @ £2k exchange. On balance I am very pleased with the KAMDs - very effective in my boat, easy to service because there is loads of room around and the few service items they need are relatively cheap compared to a 6L engine with multiple filters anodes etc.

They are more complex than an older mechanically injected engine but that unfortunately is the price for better emissions . I think on balance superchargers are a great addition to planing boat engines, You get a more responsive engine in a lighter package. Yes they are more stressed, but most boat engines fail through abuse/poor maintenance than actual wear.

 

[ari]

When the KAD300 was released, the main driver was the boat manufacturers, driven by the consumer - they all wanted to be able to advertise a higher speed, and [insert name of average customer here] wanted to be able to tell their friends in the bar that they had the fastest boat. Vanity was the means to this end, simple and inevitable.... as there was a demand, VP obliged.

Do you really think that? That people chose their engines 'to be able to tell their friends in the bar that they had the fastest boat'!?

Hilarious!