Who's living in your sail drive leg?

[Nostrodamus]

I have a volvo sail drive and was told by the previous owner to check the raw water intake often as various boat families and sea dweller like to live there.

I know that there have been at least three raw water pumps fitted to the MD22 volvo engine and the previous ones all developed leaks. (boat is 14yrs old). They are very expensive to replace.

Now I have heard it mentioned that when the boat is hauled out it is a good idea to rod or back blast the raw water intake to try and clean the inhabitants out.

What I cannot understand is why there isn't a raw water filter fitted between the leg and the pump which would stop items going to the pump and allow you to see the flow.

Is it a good idea to fit one and why isn't there one in the first place or a filter over the intake holes on the leg?

This seems to be a problem with sail drive legs and I wondered if anyone else has come across this or added a filter.

Thanks

 

[xyachtdave]

Can you break the inlet hose between the leg and impeller and fit a Vetus strainer?

My MD 2020 and 120s leg had one retro fitted. I cleaned my out recently and small bits of what appear to be mussel shell are caught in the strainer.

Assuming these bits would go into the impeller housing possibly damaging seals before clogging up the heat exchanger.

An easy/cheap fix if you can mount one high enough above the waterline.

 

[yoda]

I have certainly seen sail drives with raw water filters fitted on smaller boats. I would have thought a quick call to your original boat builders would confirm this and fitting shouldn't be a difficult task. Probably the most important thing will be to ensure you fit one that enables the water flow rate to be maintained. The location for fitting it will be dependant on space and may be above or below the waterline, if above make sure bleeding/priming it is easy so it can be done quickly if required.

Yoda

 

[aluijten]

What I cannot understand is why there isn't a raw water filter fitted between the leg and the pump which would stop items going to the pump and allow you to see the flow.
Thanks

As far as i know the "official" statement of Volvo Penta is that because the saildrive leg sits quite deep in the water a raw-water strainer is not required.

Personally I think this just a silly argument to sell more saildrives (easier installing).
I've had two boats and in both I've installed a strainer.
In all honesty the first actually did not pick up a lot of dirt. In my current boat though, I do have to clean the strainer a few times per year.
So I would strongly advise to put one in. The Vetus model is a nice one, comes in many different sizes and is easy to inspect for dirt. If you put it slightly above the waterline cleaning is easy and does not require the sea-cock to be closed.

Cheers,

Arno

 

[Nostrodamus]

Not being an expert on legs, well sail drive legs anyway, or anything else come to that the reply has thrown something up i did not concider.
Does the raw water pump on the engine pull the water through the leg and does it matter if a filter is fitted above or below the waterline?
There is a inlet valve from the saildrive leg with a stopcock. from this there is about a meter of hose to the pump. It should be a easy job to cut the hose and fit a filter in line.
I hate it when I say an easy job.. that will mean something will always happen I had not concidered.

 

[Cantata]

Yes the cooling water gets pulled through the leg.
Yes you can fit a filter and IMHO you should.
Yes it's useful to fit it so that at least the top of it is above the waterline as that means you can take the top off to clean it without worrying too much about sinking the boat.

 

[vyv_cox]

Based upon my experience with a seawater cooled refrigerator I doubt that a strainer will be very effective in deterring marine growth. I use a small Jabsco pump with an upstream strainer to drive seawater through the refrigerator heat exchanger.

Over a period of a month or so the flow rate gradually deteriorates due to fouling inside the strainer. This is mostly the calcium deposits of Mediterranean worm but some other growths also occur. Much of it is downstream of the mesh. Some of this fouling also grows inside the pump downstream of the strainer and needs cleaning from time to time.

 

[Habebty]

Or bypass the saildrive leg altogether and fit a seperate seacock and strainer, as the builders did on my boat.

 

[Nostrodamus]

Looks like a strainer then.
Does anyone clean there saildrive leg raw water intake out and what is the best way?
Does a lot come out?

 

[savageseadog]

I did actually draw a small eel up my sail drive once which hermetically sealed the water pump inlet and stopped the flow completely. It's the only time I've had a problem though in 20 years.

 

[Tranona]

Very surprised if you do not have a water filter between the inlet and the pump. It is standard fitment on many boats (even my bargain basement Bavaria) and is any easy retrofit if not there. Mount it on a bulkhead above the waterline where it is accessible to remove the cap for cleaning. Run the hose from the fitting on the saildrive to the filter and another from filter outlet to the pump. The Vetus filter comes with full instructions.

Although it does happen, blockages from things growing in the water inlets are not common, but if you do suffer (and it tends to be location specific) then it is not difficult to have a separate inlet and valve. Ideally this should be vertically below your filter so that you can clear any blockages with a rod. It is also possible to retain the saildrive inlet and have a changeover valve for a real belt and braces job.

When the boat is out of the water, check the inlets. You can scrape the beasties out - they die out of the water and then blast through with water to clear debris.