400 Sundancer Cruise Speed

[Graham Lorimer]

I am aware that my 350HP CAT diesel powered 400DA should achieve 22 knots at 2200rpm when it is clean and lightly loaded. It does this no problem, however I always like to check that everything is in order, by checking speed to RPM.

When we leave the Marina for a two week trip to the islands, with 1200 litres of fuel, 400 litres of water in the tanks, an extra 100 litres of water in solar shower bags, full food and drink lockers, two of us on board, RIB on the TNT Lift with 40 litres of fuel in it, and all the normal "stuff" including a 70 pound liferaft, needed for two weeks on the hook, what speed should the boat make at 2200 rpm on a flat sea.?

We always have a lift and clean before leaving for an extended trip, and being the Mediteranean, there is minimal tide or wind to allow for in the calculation. How many knots short of the optimum would be considered "normal", given the loading.

Grateful for anyones input on this, based on your own experiences.

Thanks

Graham

 

[osd9]

I have a 410DA with 3126-TA CATs. Very similar boat. I do NOT have a TNT lift. I carry an inflatable with a 5 hp outboard loaded on a pair of platform mounted Dinghy Davits.

A few things to clear up first...and be honest:
----With the boat FULLY loaded can you reach 2800-2825 RPMs?
----Are you reading your RPMs from the factory analog tachs or a set of very accurate Digital tachs?

If you can't reach rated WOT RPMs AND read the RPMs accurately, then my info below may or may not be helpfull.

Fully loaded I can easily reach a WOT of 2850 RPMs +/- a few Rs.

When I'm light on fuel, water and stuff, I can easily make 22 Knots at 2250-2275 (accurately measred) RPMs.

When I load up on fuel, water, dinghy and stuff, I would need to bump the RPMs up approximately 100-125 RPMs to achieve the same speed.

I hope that helps....

 

[indecision]

i had the 400 with same engines , 1999 , no lift , ran 28 MPH at 2600 rpms . wot was 2850 and speed was 33 MPH >.

 

[Searaybio270]

Interesting posts. I am headed to Florida to look at 4 Sea Ray 400 EC. One has CATS. All are between 1996 to 2000.
Is there a manual or something like that, that will give you what RPM at what speed?
I think this would be helpful to know if a boat is performing to SR specs or at least close to it due to age.
Thanks,
Crusing on the Cheseapeake Bay

 

[Graham Lorimer]

My boat makes 22 knots at 2,200rpm and 28 knots at 2,830rpm, this is all to spec. and when it is lightly loaded, ie going out for a day cruise.

My query is, based on previous experience, can someone tell me what it would therefore make with the loadings as described at 2,200rpm.

Thanks

Graham

 

[osd9]

I can't speak for the gas motors, but as to perfromance of the 400 EC with CATs, you need to be able to 'accurately' confirm that the motors reach a 'minimum' of 2800 RPMs at WOT with a full load. If the boat doesn't have full fuel, water and stuff, then grab a bunch heavy dudes at the dock and ask them to go for a boat ride.....keep in mind that a full load of fuel alone is close to 1 TON....Water another 1/4 TON....and Stuff....geesh....that could easily go over another TON.....

The EC is straight drive and should cruise at a higher speed then the DA. I'd guess in the mid/upper 20 knot range....say 24-27 kts....at 2400 RPMs.

HOWEVER....nothing will be more important than hull and engine surveys by competent and qualified professionals....CAT certified for the motors.

I'll go out on a limb and say the fwebster will surely help you if you decide move on the CAT powered vessel.....

 

[Searaybio270]

Thanks for the info. Time will tell