Ask the Experts
Q
I have a Frances 34 Pilothouse, with two steering positions and a below decks electronic autopilot. The internal steering and autopilot are hydraulic – the cockpit wheel is connected directly to the Whitlock system and does not use the hydraulics.
It is a two-pipe unpressurised system.
Starting from the internal helm, there is a Hydraflex hydraulic fluid reservoir behind the wheel. Nylon hydraulic lines run down the binnacle, under the wheelhouse floor to a Raymarine 0.5 pump. The hydraulic lines connect to the pump via brass T-connectors.
Ahead of the pump is a solenoid valve from which the hydraulic lines run to a Hydraflex ram. This is a 35bar rated 170cc ram with a 19mm piston connected to the rudder stock.
Buttons at each helm control which wheel is in charge and there is a switch for the autopilot system too.
All this kit is 1997 and I doubt the ram has ever been serviced. The Raymarine onboard electronics, however, are all new.
After prolonged use, I get an error message on the Raymarine control head and the autopilot gives up.
There is evidence that air gets in to the system and I currently have what looks like half a cup of hydraulic fluid in the sump under the engine. But there’s no other obvious evidence of leakage: the shaft of the ram does not appear to be pitted and I have just drained and refilled the system. I got a lot of air out – possibly not all – and don’t seem to have got the requisite amount of fluid back in but it won’t take any more. It is currently working but it has not been put under pressure or used for many continuous hours since bleeding and refilling.
I have placed kitchen towel under the ram, steering pump and T-connectors to monitor leakage.
Questions:
1. After 21 years, is it better to replace or service the ram? Do I need 170cc? 2. The Raymarine pump should be the 1.0 model for a 170cc ram. Is it undersized? Might this be an issue?
3. Should the old brass T-connectors be replaced by a better modern equivalent?
TONY DAVIES REPLIES I’m not familiar with your system that uses buttons to select which wheel is used. I presume that is the purpose of the solenoid valve. Hydraulic systems usually automatically switch between wheels without any need for selection.
You clearly have a leak and until you find it you’ll never have a reliable system. I have never known a ram to wear out on a leisure vessel and the size of ram should not be causing any problems.
You should speak to Raymarine to ascertain the meaning of the error code and at the same time you can ask for their opinion on the suitability of the autopilot pump on your current system. Generally an undersized pump will have to work harder and may not provide optimum steering performance.
Brass T-connectors are standard for use on hydraulic steering systems so unless they are leaking should not need replacing.
If you have bled the system in the usual way by turning the helm fully to port then opening the bleed valve on the starboard side of the ram and removing air by turning the wheel further, then reversing the procedure for the other direction then doing the same with the autopilot the system should be free of air.
In any case when the boat is out of use air will slowly work its way up to the helm pump and then to your reservoir which will help the situation.
Once the leak is cured and you have spoken to Raymarine you’ll be able to decide what steps to take with regard to the autopilot pump. In general, hydraulic steering systems are quite simple. Finding problems such as leaks can be tiresome but once sorted should not cause further problems.
Q
Since I launched my Westerly Pageant after a restoration project, all was well with the Yanmar MG10 until the last trip, where having only travelled a few miles I noticed a change in the sound from the engine.
Suddenly there was smoke billowing out of the engine compartment! I stopped the motor and allowed the smoke to clear, which was when I discovered the exhaust inlet pipe had melted allowing the exhaust smoke and cooling water to discharge into the engine compartment.
I contacted Vetus and they suggested that the length of pipe from the manifold, which allows time for the exhaust gases and cooling water to mix, might be too short. They said it should ideally be 500mm, yet their installation illustration states a minimum of 300mm and mine is 360mm.
They also suggested another possible cause might be the size of the takeoff pipe that sends water to cool the prop bearing.
Clearly the meltdown was caused by the lack of cooling water, and while both of the above could have been the cause they would not explain the sudden loss of coolant as the system had been working for a number of months prior.
Any thoughts on what the cause could be?
STU DAVIES RESPONDS The cooling water is ejected from the engine and into the exhaust system through the water injection elbow. This water not only cools the exhaust system, it also silences the exhaust note. The change in the sound of the engine could have been the unsilenced exhaust, ie no water going through it. So why did it happen?
If it has run for much longer previously, then the system set-up sounds OK. Vetus could be right about the size of your outlet to the prop shaft bearing? With the boat pitching in rough weather it's possible that the water inlet was not picking up enough water and too much was going to the prop shaft instead of the exhaust...
Having said that, the first thing I would do is check for evidence of obstructions in the water inlet and the water pump impeller. You might have picked up a plastic bag on the intake which stopped the cooling water flow temporarily and gave you the change in note of the engine. With no cooling water flowing, the rubber and plastic would have melted, then the obstruction could have dropped off the intake and water would have resumed being pumped through again.
If all seems OK then some thought could be given to the outlet to the prop shaft. On my Beneteau with a 30mm Volvo Seal, the cooling water pipe connection is only 6mm wide to it. A simple pipe thread bushing in to that tee to reduce the size would perhaps slow the flow and allow more water to the exhaust.
MALCOLM SOTHERN FOLLOWS UP:
I hadn't done much rough weather sailing and as a DIY restoration project perhaps the shakedown was needed to show up a few weaknesses in my systems. But having said that, I checked the size of the pipes to the prop bearing and all is standard. I also checked for wear on the impeller plate, but found none. I have replaced the damaged section of waterlock, reconfigured the water intake, extended the exhaust to 400mm and installed an anti-siphon on the exhaust. Since installing a temperature alarm and correctly calibrating I have not had a single problem. So hopefully all sorted!