Yanmar 3GM & multiple sea-cock

[Gazza]

I am in the process of buying a Vancouver 32 fitted with a Yanmar 3GM (30hp) engine. The impellor is situated with the cover facing away from the front of the engine, i.e. back into the engine compartment. I had a similar situation on my last boat, but there was sufficient room to get at the cover and I fitted a Speedseal for peace of mind.

However, there seems little, if any, room to get at the impellor cover without dismounting the whole unit. Is it possible to reverse the unit on a bracket?

The engine water inlet sea cock is located at the rear of the engine compartment, and is also awkward to get at. There is a sea cock located in front of the engine which is currently used for a deckwash powered by an engine driven bilge pump. I could, I suppose, swap these round, but am wondering if it is possible to use a sea cock with two pipes from it. Some sort of manifold would be necessary, and a valve in-line to shut off the deckwash hose when not in use. Would this work - particularly on the issue of whether a single sea cock could produce the necessary quantity of water for engine cooling and deck/anchor chain wash at the same time.

Any ideas gratefully received.

 

[Strathglass]

In theory yes but in practice may have problems.
The cooling impeller on most engines has a rather limited performance as a result of value engineering by the manufacturer. In the past I have found that, if you use too large an input seacock the impeller pump will have problemsin starting to pump. Also if the path from the inlet seacock to the impeller has too many obstructions (bends) and is very long you could have cooling problems. In your case the deck wash pump may be so much more powerful than your impeller pump to such an extent as to rob the impeller pump from gettimg any water for wngine cooling.
If you wished to pursue your idea you could use a Y shaped splitter which are readilyavailable.
I would sugest however that you proceed with caution.
Iain

 

[gunnarsilins]

On my Moody 42.....

...I have only one seacock under waterline. This single inlet supplies the engine (Perkins 4.236) cooling system, two Lavac toilets, one foot pump with tap in the galley and a deck washing pump.
The intake is one size bigger than the original "cooling only".

I have fitted non-return valves in all hoses exept the engines coolant hose. This to ensure that the engine does not draw water from elsewhere except the sea.

I made up this system for this yacht three years ago, because I keep the her afloat all year around in Stockholm/Sweden. I just want one single seacock to bother about and filling up with anti-freeze when it gets really cold.

I had exact the same installation on my previous yacht for almost ten years and it has always worked well.

 

[ccscott49]

Re: On my Moody 42.....

I agree with you, one seacock will do, after all your not continually pumping the heads, sea water and engine all at the same time, so if the toilet does take a little engine coolling water, so what its only for a minute or two. Non-return valves are an excellent idea. But keep am eye on them, they have a habit of sticking. But I guess you know that anyway.

 

[vyv_cox]

Re: Yanmar 3GM

I agree about the impeller cover and have posted something similar previously. I found it easier to take the pump off than to remove the cover in situ. It might be possible to design a bracket that would reverse the pump but the hose connections would then be on the wrong side. It's not a major job to remove the pump but a lot more time consuming than just taking off the cover. All I do to avoid problems is to fit a new impeller every season.

 

[Guest]

Re: Yanmar 3GM

Small point here folks, the 3GM pump is belt driven,surely if you reverse it on a bracket the pump would then run backwards? Anyway we have 2 of these engines in our club boats and I find it very easy to remove the pump from the engine and do any maintenance.