Cruising.Boat Racing Engine. Why?

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.

Not 'to be able to tell your friends in the bar that you have the fastest boat' then..?

Interesting...
 
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! :D

Think it! I've seen it first hand... at the RMYC in Poole and when I worked for a CRANCHI dealer in the US.

I used to work as a commissioning engineer, we were sworn to secrecy when new engines were being released. The engine manufacturers work closely with the boat builders to ensure stock is run down on old models before the new ones are released as it became very hard to shift the "old" models as soon as there was a new variant. There are a few tricks employed to help out wit this (such as a boat builder launching e new model or model variant to coincide).

Hilarious it maybe, true it certainly is ;-)
 
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! :D

Well, maybe not, but there were plenty of people that wanted a 30kt boat, even if they cruised at 23kts.
 
My Hunton 36 had twin KAD 44's with worked Stainless steel props. Top speed of 48 knots and very quick on the plane. we used to get to the end of 6 knot limit on Southampton Water and then ease throttles and before you knew it you were doing 30 knots and increasing speed, Great fun. Would cruise at 32 knots for 3000RPM economical as well at that speed approx 30 Litres per hour per engine, WOT was only 57 Litres. did have a supercharger issue once when it would not cut in. Really struggled to get on the plane .
 
Well, maybe not, but there were plenty of people that wanted a 30kt boat, even if they cruised at 23kts.

Oh absolutely agree. The number of people who want the fastest boat certainly does not equal the number of people who use the potential. But that is rarely the point ;-)
 
Think it! I've seen it first hand... at the RMYC in Poole and when I worked for a CRANCHI dealer in the US.

I used to work as a commissioning engineer, we were sworn to secrecy when new engines were being released. The engine manufacturers work closely with the boat builders to ensure stock is run down on old models before the new ones are released as it became very hard to shift the "old" models as soon as there was a new variant. There are a few tricks employed to help out wit this (such as a boat builder launching e new model or model variant to coincide).

Hilarious it maybe, true it certainly is ;-)

And you think people wanted the newer model just to give them bragging rights in the bar? Remarkable. :)
 
Well, maybe not, but there were plenty of people that wanted a 30kt boat, even if they cruised at 23kts.

For sure there are, I'm one of them.

I also want a car that will cruise comfortably at 70mph and for the exact same reason, I don't buy a car that will do 71mph flat out because that's technically sufficient for my needs.

It had never occurred to me that anyone would believe for a second that this was purely for 'bar bragging rights' however. :)
 
And you think people wanted the newer model just to give them bragging rights in the bar? Remarkable. :)

No, please don't misunderstand me. I'm not trying to imply that this was the only reason, just that in the context of the thread, I was making the point that the engine manufacturers produce what the market wants, and not the other way around. Even though, as we have agreed the full performance potential is rarely fully used, it is is still demanded.
 
Some very enlightening replies and I now understand why we have the type of engines we have, I guess it’s true a slower reving normally aspirated engine could still have issues and not struggling to get on the plane does add to the driving experience
I wonder if my next boat may be a bit of a plodder, cruising at around 6-8 kts?
OK until you feel the need to push on I suppose, guess then I’ll be glad to have my turbos!
 
We had a sealine 360 statesman with kad42 on shafts and It didn’t really need the superchargers at at. It would plane with 8 adults on board and big rib hanging off the back with the super chargers disconnected , I would regularly pull the plug on chargers if we went into pool harbour because if you had tide going against you but you could only do 5/6k before the chargers kicked in and it would put belt dust all Over the the engine room not to mention the noise, and I’m sure it can’t be doing the engine much good to have the super charger running constantly, I always planned to put some switches on the dash but never got round to it
 
I understand it to be perfectly OK to run at such a speed that the supercharger s are constantly engaged
Although tend to throttle back a bit to below 1200rpm as the noise can be a bit off putting
Mind you, on the fly bridge with the wind blowing can’t hear the engines anyhow

PS. Think the KAD44 is a great motor and very happy, was just seeking opinions and thoughts of others
 
We had a sealine 360 statesman with kad42 on shafts and It didn’t really need the superchargers at at. It would plane with 8 adults on board and big rib hanging off the back with the super chargers disconnected , I would regularly pull the plug on chargers if we went into pool harbour because if you had tide going against you but you could only do 5/6k before the chargers kicked in and it would put belt dust all Over the the engine room not to mention the noise, and I’m sure it can’t be doing the engine much good to have the super charger running constantly, I always planned to put some switches on the dash but never got round to it

Poole harbour was a bugger for that - just on the limit where the compressors cycle. If there was any corrosion on the pulleys it would eat belts...

The other tip we would give was to run out on one engine and back in on the other. The load was then high enough to stop the cycling, and using each one each way kept the load and hours even.

I knew quite a few people who fitted switches to the mechanical KA(M)D's, it was a popular mod in Poole for inboard boats particularly :cool:
 
Poole harbour was a bugger for that - just on the limit where the compressors cycle. If there was any corrosion on the pulleys it would eat belts...

The other tip we would give was to run out on one engine and back in on the other. The load was then high enough to stop the cycling, and using each one each way kept the load and hours even.

I knew quite a few people who fitted switches to the mechanical KA(M)D's, it was a popular mod in Poole for inboard boats particularly :cool:


that’s good idea ? never thought of using just one engine and and keeping it above the revs that the supercharger kicked in ,
sold the boat in December ,going back on inland water ways for bit ,didn’t think it was good idea to run that kind engine on the river so bought boat more suited to the river without super chargers
 
that’s good idea ? never thought of using just one engine and and keeping it above the revs that the supercharger kicked in ,
sold the boat in December ,going back on inland water ways for bit ,didn’t think it was good idea to run that kind engine on the river so bought boat more suited to the river without super chargers
You should mention that to the 1000's of KAD engined boats pootling up and down the river (Thames), none seem to suffer that much.:)
 
You should mention that to the 1000's of KAD engined boats pootling up and down the river (Thames), none seem to suffer that much.:)

tell that to the person who bought our boat, he paid more to buy our boat ,
he was offered a similar boat on the Thames for cheaper but he bought ours specifically didn’t want one that had been pottering up and down the river at 6knots
 
My Hunton 36 had twin KAD 44's with worked Stainless steel props. Top speed of 48 knots and very quick on the plane. we used to get to the end of 6 knot limit on Southampton Water and then ease throttles and before you knew it you were doing 30 knots and increasing speed, Great fun. Would cruise at 32 knots for 3000RPM economical as well at that speed approx 30 Litres per hour per engine, WOT was only 57 Litres. did have a supercharger issue once when it would not cut in. Really struggled to get on the plane .
That’s incredible. What would she rev to at 48 knots ? Did she have a much higher gear ratio in the drive than normally found ? Maybe not...if she was also quick to plane too. Incredible numbers there. Fast hulls.
 
That’s incredible. What would she rev to at 48 knots ? Did she have a much higher gear ratio in the drive than normally found ? Maybe not...if she was also quick to plane too. Incredible numbers there. Fast hulls.
Duo props are also known for quicker acceleration. 48 knots was WOT at 3800. Used to cruise usually around 32 knots but did once come back from Studland bay at 40 knots all the way back to top of Southampton Water,

I had a friend ensure that all the blades were pitched exactly the same, Unfortunately I do not know what the gear ratios as I sold the boat in the summer and no longer have the information,

It was interesting hearing from the broker whom drove the boat to Poole for the new owner, he said of all the boats he had driven the Hunton was just effortless at speed. he was very impressed
 
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