Sunseeker portofino 31 Twin KAD44!!! 520hp

M

myultrasound

Active Member
Joined
8 Feb 2016
Messages
60
Visit site
Hi,
Took my friends boat over to hard standing, its having a refit before selling..
It had brand new KAD44's with edc fitted in 2002

Check out these figures: Its like a rocket!!

2000 rpm planing at 18knots

2500 rpm 25 knots

3500 rpm 38 knots

3800 rpm 47 knots

https://youtu.be/uFvR00LYHvE
 
myultrasound said:
Hi,
Took my friends boat over to hard standing, its having a refit before selling..
It had brand new KAD44's with edc fitted in 2002

Check out these figures: Its like a rocket!!

2000 rpm planing at 18knots

2500 rpm 25 knots

3500 rpm 38 knots

3800 rpm 47 knots

https://youtu.be/uFvR00LYHvE
Click to expand...

Hmmn I think you might have been a bit generous with your figures! 47 knots over the standard boat with 400hp that hits 30? The video looks like the boat has been stripped for the refit?
 
Hi,
Standard boat with 41's is 36 knots.

Any 31 owners disagree with that??

Yes its stripped.. All of it is in the cabin..

Thanks!
 
Last edited:
myultrasound said:
Hi,
Standard boat with 41's is 36 knots.

Any 31 owners disagree with that??

Yes its stripped.. All of it is in the cabin..

Thanks!
Click to expand...

I think the most I ever saw on mine (with 41s) was 34 knots but it's a long time ago that I sold it and memory may be faulty. I'm pretty sure that 30 knots was maintainable for long periods at WOT- X

I would have liked to have had KAD44s in back, tho' and that one looks excellent. :cool:
 
Not bad. Struggled to get 31 knots out of my Portofino 31 when I had her. Kad 44's in a Portofino sounds nice.
 
blimmen heck that thing is quick. Forget the figures, just look at her go. Surprised the bimini didn't rip off.
 
I have 42's. Unless I'm mistaken without the superchargers they are 41's. When I repaired and replaced my superchargers the difference the extra hp gave me was eye opening allowing me to put on a bigger prop etc. Without the superchargers the larger props restricted me from developing enough power to get on to the plane and the torque curve although the engine once it had reached it's optimal torque curve was more than capable of supporting these props as witnessed when the superchargers cut out currently. As such I cannot see the correlation of top end speeds based on HP alone and do not therefore question the OP's figures.
 
Your point is irrelevant (no disrespect) as the engine at that rpm is running with the supercharger disconnected, turbo engaged and the boat is already on plane.
 
Whilst I understand props "slip" in the water, I do not understand the significant jumps in speed compare to engine rpm.





2000 rpm to 2500 rpm = 500rpm increase and 7 knots speed increase = 71 rpm per knot

2500 rpm to 3500 rpm = 1000rpm increase and 13knots increase = 76rpm per knot

3500rpm to 3800rpm = 300rpm increase and 9 knots increase = 33rpm per knot
 
Last edited:
Stats007 said:
Your point is irrelevant (no disrespect) as the engine at that rpm is running with the supercharger disconnected, turbo engaged and the boat is already on plane.
Click to expand...

No, I think you missed my point. The 41 (or 42 without superchargers) cannot take a bigger prop or it will not get on the plane in the first instance so in a compromise lets say it's prop size is the equivalent of 2nd gear for simplicity sake, whereas with the superchargers on the engines can get on the plane with significantly coarser props. Say 4th gear. Same HP reached at WOT but a massive difference in top end because the finer coarse pitch props cannot make full use of, or translate the power of full HP at top end revs because of their compromise in being able to get the boat to the plane below the torque / hp curve
 
Last edited:
mlines said:
Whilst I understand props "slip" in the water, I do not understand the significant jumps in speed compare to engine rpm.





2000 rpm to 2500 rpm = 500rpm increase and 7 knots speed increase = 71 rpm per knot

2500 rpm to 3500 rpm = 1000rpm increase and 13knots increase = 76rpm per knot

3500rpm to 3800rpm = 300rpm increase and 9 knots increase = 33rpm per knot
Click to expand...

The first two are roughly synchronous, the third could equally be explained by a reduction in prop slip because the hull has reached a tipping point and is much higher out of the water reducing drag and slip. I know on my own boat she really seems to only break free and start skimming at ~25knts. As such I can be doing 3200 rpm and be sub 25 knts and if on calm waters she will suddenly lift and without increasing rpm improve her speed quite markedly.
 
Hi all, wow what a response..

Okay, the boat has all the exterior and interior taken out for re-upholstery.. Obviously a lot lighter now.
We are taking the boat to St feliu for the hull to be painted blue on Saturday.. I will take the boat to full rpm's with video..
The boat's props are not in great condition a little chipped, new ones on the way. Size B6.
Engines were brand new 2002 as were the drives and only done 450 hours since.. Previous engines were type 41a
Thrust from the hole shot is instant with no lag.
I cannot understand why the owner from 2002 would pay €72,000 (my friend showed my all the old bills)for this install, either the owner was rich, or the sales guy was very clever!!
I am not embellishing the truth, it planes out at 2000 rpm.. 25knots is a nick above 2500..
Best regards..
 
Are we talking GPS speed or paddle wheel speed?
Is there any tide to be taken into account?
Up or down hill?
Sorry for the questions but the top speed seems a bit unrealistic..........
 
BruceK said:
No, I think you missed my point. The 41 (or 42 without superchargers) cannot take a bigger prop or it will not get on the plane in the first instance so in a compromise lets say it's prop size is the equivalent of 2nd gear for simplicity sake, whereas with the superchargers on the engines can get on the plane with significantly coarser props. Say 4th gear. Same HP reached at WOT but a massive difference in top end because the finer coarse pitch props cannot make full use of, or translate the power of full HP at top end revs because of their compromise in being able to get the boat to the plane below the torque / hp curve
Click to expand...

No I understand completely, however it's still irrelevant. To make use of the extra power the drives obviously have courser pitch props or the engines would over-rev. My experience tells me that you need quite a bit more horsepower to get anywhere near 47 knots in a boat of that size and weight. I suspect 42 knots when refitted is more realistic.
 
myultrasound said:
I am not embellishing the truth, it planes out at 2000 rpm.. 25knots is a nick above 2500..
Best regards..
Click to expand...

If 2,500rpm is 25 knots then it follows (give or take a knot) that 3,800rpm (max revs) is 38 knots.

Which, to be fair, sounds a more realistic uplift from circa 33 knots max with twin AQAD 41 200hp for an extra 30% power.

Are you absolutely certain that the GPS wasn't reading MPH? 47mph is about 40 knots, give or take.
 
Last edited:
Hi,
If weather is good on Saturday, we will video WOT.. The video posted on here is at 3500rpm.
In answer to a question, no tides to talk of in South Spain and wind was about 12knots.
Props are B5's in quite poor condition, new ones are being fitted.
 
Stats007 said:
No I understand completely, however it's still irrelevant. To make use of the extra power the drives obviously have courser pitch props or the engines would over-rev. My experience tells me that you need quite a bit more horsepower to get anywhere near 47 knots in a boat of that size and weight. I suspect 42 knots when refitted is more realistic.
Click to expand...

Sealine s38 with the same motors has a top speed of 35knots.. Imagine the size and weight difference between the two..
 
Happy to stand corrected - will be interesting to see what she does when refitted.

I almost bought a Hunton 36 which had twin KAD300s - significantly narrower beam and lower weight than a Portofino and that would only do 45 knots so I'm a bit sceptical!
 
You must log in or register to reply here.

Share this page

Top