Princess 435 questions

I had a 435 with 358hp TAMD71A engines and that would max out at about 28kts. With TAMD61As you'd be lucky to see 25-26kts. Cruising at 20kts you should get about 0.9nmpg. The 435 is an excellent boat with a huge amount of accommodation in a very good hull. As with most aft cabin boats access to the engine bay is tight in some areas so try to get into the less accessible areas to check the condition of the engines and ancillaries
 
Lovely boat...
My father has a 385 with the Tamd61A's. Probably slightly lighter but similar hull. He finds it most economical at around 10-14 knots in displacement form and at around 1200-1300rpm, from memory. Will top out at around 29knots but wouldn't even like to think about the diesel she sucks at that speed and the wake can be embarrassingly large when in close proximity to smaller boats in the Clyde !
I've serviced the engines annually for the past 7 or 8 years and touch wood run great as long as you keep on top of things.
Things to look out for would be;
leaking water pumps at the fwd end of the engine and spaying onto surrounding ancillaries and engine mounts, causing corrosion.
The starboard oil filter is a bugger to change if the remote kit isn't fitted. Best to remove oil pipes and while assembly to change.
Reverse gear oil cooler sw outlet pipes to shaft gland cooling can leak also causing corrosion
Stainless steel exhaust pipe from turbo weld seem can become weak through movement over the years. Had to get his re welded.
Change the injectors or better still get them overhauled. Any good fuel specialist can do this. Wasn't terribly cheap but well worth it, (Think it was £30-40 each x12) if they haven't been done already. Vastly reduced start up smoke and slight diesel carry over out the exhaust and evident in water at outlets.
Other than that, superb and silky smooth engines and don't worry about a bit of smoke at start up from cold. Soon disappears if the injectors have been done.
All the best, Allan
 
10-14 knots is way above displacement speed for a 435, never mind a 385.
Maximum displacement speed for a 435 is going to be somewhere around 8knts assuming a WLL of around 36ft (based on a ex-pulpit length of 41ft).

At 10-12 knots she'll be climbing the hump and likely burning more fuel than if on the plane
 
Thanks for all the info guys, quotes received so far to transport her back are around £8500 . Question I had a thought to bring her back in 3 or 4 stages over 12 to 18 months ,the challenge is 2900 miles. 300 hours cruising at displacement speed ,so would it be wise to run each engine in turn for 2or 3 hours or will this cause any issues with the other shaft,gearbox etc.
Ideas please.
 
Oh Jeez....always someone that knows better I suppose...
At the risk of a silly argument, the 385 will certainly sit at 10 knots, if not 12 in a displacement form. Fact.
Simply trying to offer some advice and knowledge given experience with a similar boat and around 20 years as a MCA certified Marine engineer
 
Hopefully my advice was helpful enough and I'd certainly be interested to hear how you get on....sounds like a great adventure. Just watch the temperature of the non running engines shaft gland if you run with one engine and the other prop spinning. Should be grand though, I'm sure at low speed.
Not sure of the props you have, but my fathers have fairly fiercely pitched 4 blades. She will do just under 7 knots at barely over tick over on both engines. Great for open water cruising, not so much for the Caledonian canal....as we recently found out !
Good luck, Allan
 
QBhoy said:
Oh Jeez....always someone that knows better I suppose...
At the risk of a silly argument, the 385 will certainly sit at 10 knots, if not 12 in a displacement form. Fact.
Simply trying to offer some advice and knowledge given experience with a similar boat and around 20 years as a MCA certified Marine engineer
Click to expand...

It will sit at 10knt or 12knts for sure - but that is above displacement speed.
Regardless of how long you have been an engineer, you can't beat physics.
 
I wound not bother alternating engines.

The fuel saving will be minimal, directional control less and if it has power steering this will be run by one engine making it difficult to steer when on the other.
 
QBhoy said:
Oh Jeez....always someone that knows better I suppose...
At the risk of a silly argument, the 385 will certainly sit at 10 knots, if not 12 in a displacement form. Fact.
Simply trying to offer some advice and knowledge given experience with a similar boat and around 20 years as a MCA certified Marine engineer
Click to expand...

The maximum displacement speed (hull speed) is given by 1.34 x the square root of the waterline length. Say the waterline length of your 385 is 33ft then the max displacement speed of the 385 is 7.7kts. Therefore whitelighter is quite correct. If your 385 is doing 10-12kts it is partially planing

https://en.wikipedia.org/wiki/Hull_speed
 
QBhoy said:
Oh Jeez....always someone that knows better I suppose...
At the risk of a silly argument, the 385 will certainly sit at 10 knots, if not 12 in a displacement form. Fact.
Simply trying to offer some advice and knowledge given experience with a similar boat and around 20 years as a MCA certified Marine engineer
Click to expand...
Define "sit". If you mean that she's not flying, she surely ain't also at 30 knots... :)
But since you mentioned facts, the FPB 64' is one of the fastest D monohull (of her size) that I'm aware of - capable of cruising at 9/9.5 knots. And that's with an extremely efficient D hull, just shy of 20m LWL.
If your father's P385 can outperform that, being "most economical at around 10-14 knots in displacement form", Steve Dashew might be interested to buy her...
 
MapisM, if not already aware, you may be interested to know the latest variant (FPB 78) is due to commence trials within the next week or so. I'm eagerly awaiting a full report on the finished product.

Sorry for off topic.
 
Surely he is just taking about semi-displacement speed, that is the point where the boat is climbing over its bow wave but not actually over it and planing on the surface of the water. Usually that is the most awkward speed for full planing boats, say 8 to 15knts or so and the most uneconomical speed to travel at pushing a huge bow wave with the bow pointing at the sky. Loads of SD boats designed to run specifically at those speeds, Broom, Nelsons etc.. however a P385 has full a planing hull but an old design so it might be comfortable at 10knts but its most economical speed will still be just below hull speed at 6/7knts.
 
I actually purchased my P435 two years ago, she has the 61a engines.

Deleted User is quite correct, with her engines now 25 years old its hard to push it up more than 22 knots. But speed is not really the point! The 435 is a fantastic boat for the money these days, lots of space and an aft cabin most modern boats of this size don't have. Lovely hull and a very comfortable ride. This boat was built to last and so speed is not really The issue. If you want speed buy a much newer and lighter boat.
 
Yes Whitelighter is right no problem with that sort of speed, but even Hurricane has told me he's quite happy to cruise at ten knots to save money on fuel and the same applies to the P435.
 
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