Saildrive raw water intake

[Ammonite]

Having just experienced a complete blockage of the raw water intake with weed (the fibrous, matted type I think is called gutweed?) Ive decided to fit an additional seacock that won't collect weed in the way the saildrive does when its sat on the mooring. My question is whether I should isolate the existing intake, tee them together or fit a y valve between the two? Thanks.

 

[Crazy-Diamond]

I'm not an expert, but I think on my Yanmar SD20 saildrive the raw water coming up the leg is needed to cool the gearbox. If you bypass this then perhaps it will overheat?

 

[asteven221]

Yes I thought of doing that on my boat.

Someone mentioned gearbox cooling could be an issue, but have not yet investigated any further as the boat is in the water. What I have done is store a long hose in the bilge which I can use as an emergency cooling hose, by connecting it to the toilet seacock and running it to the raw water filter, thus bypassing the leg.

Another thing I came up with as the boat is in the water was to close the saildrive seacock, remove the hose, connect a new hose about 1m in lenght, then open the seacock. The hose was held vertically so I could get a straight prod with a long rod into the saildrive to try and clear debris. The idea of the hose was to try and stop water ingress in to the boat from the saildrive. It worked quite well although water did (slowly) come up the hose, but that could easily be emptied in to a bucket. I simply repeated the process until I reckoned the debris was clear. That is for internal debris, but for external weed I think a pole with a brush in the end of it might work to clear external weed. Other than that dive in and clean it!!

 

[asteven221]

BTW if is recall correctly, the drive on my boat is a Volvo 120S. The engine is D2-55.

 

[RichardS]

I'm not an expert, but I think on my Yanmar SD20 saildrive the raw water coming up the leg is needed to cool the gearbox. If you bypass this then perhaps it will overheat?

The small front intake is indeed supposedly for gearbox cooling but with the auxiliary engines we're talking about on yachts and the fact that the saildrive leg is fully immersed, I can't see that overheating would ever be an issue.

Richard

 

[Tranona]

Useful to fit a separate intake but not as a substitute for the standard one but for use if you do get a blockage as described. Therefore needs a T and a valve to change from one to another. Biggest challenge with many boats fitted with saildrives is finding a convenient location close to the engine that is not double skinned. I investigated this when contemplating taking my boat through the Canal du Midi which is notorious for weed and the only location was in the aft cabin in front of the fuel tank which meant a lot of work running the hose into the engine compartment. In the end we did not do the trip so went no further.

Actually in over 20 years of owning a saildrive, have only once had anything around the leg - a big plastic bag which got chewed up enough by the prop to clear the water intakes. Equally never had problems with lodgers in the water passages, but that problem is usually location specific.

 

[Ammonite]

Thanks for the replies. If the suggestion is to stick with the saildrive inlet under normal circumstances I think the most sensible option will be to carry a couple of metres of additional hose as I can easily swap over to the heads inlet. Not as quick as flipping a couple of valves but as everything is readily accessible it will only take a couple of minutes. Thanks

 

[Daydream believer]

You could disconnect the engine end of the hose & give a blast from the dinghy pump in reverse down the pipe to see if that helps. If in a marina then a hose pipe could be hooked up & ordinary water pressure might help clear small amounts of debries. But like Tranona, my usual culprit is polythen. Reversing tends to help. Otherwise a spare length of hose that I carry, hooked up to the sink seacock in the heads is the answer

 

[johnalison]

I’ve only had a blockage once, in Salcombe with weed. We limped back to the Bag and a kind gentleman left his companions with their drinks and dived for it. The bottle of wine that I was able to give him seemed a modest reward for the trouble he saved us, so, many thanks if he is a member here. I have used the dinghy pump once or twice to confirm that there was no blockage, when the water pump was playing up.

 

[Ammonite]

Fortunately I was close to the mooring when it happened and was able to reverse flush it with a hose. Otherwise I would have used a pump. Rodding didn't help and there was quite literally no water coming through it was that blocked. I've only been back in the water a week after having the saildrive replaced so Im hoping Ive just been unlucky. If it happens again I shall definitely go down the additional seacock route.

 

[Spirit (of Glenans)]

BTW if is recall correctly, the drive on my boat is a Volvo 120S. The engine is D2-55.

As is the saildrive on mine. When I had a similar problem I did the same as you did with the extra metre of hose, but I was unable to rod it either with a drain snake or a length of stiff wire, and eventually solved the problem by simply blowing down the hose.

 

[Slowtack]

I installed a valved skin fitting years ago piped into the raw water intake pipe from the saildrive. Rarely used it, mainly as a comparator to check on flow rate thru the saildrive.