Mahe 36: Sail Drives and Props

[Jef & Marin, Netherlands]

Before making separate thruhulls, I'd spend some thoughts about the risk of drawing air in.
You only need to draw little air into your seawater cooling system to get overheating of your engine.

Could you alternatively use a spray can to spray some antifouling in the coolant intake of the saildrive, in high growth seas? You have to dry out the ship anyhow once a year to change your propellor anodes (with the Volvo folding props)

[colemj]

In 14 years with a separate thruhull instead of the saildrive intake, we have never had air lock or ventilation problems.

Even if one occasionally drew in air (lifting a hull while motoring?) it is not a problem as it will pass through the system immediately. Raw water circuits are actively pumped and do not have air trapping spots in them.

The fresh water side is different - it uses a passive circulation pump and has air traps - that is where a little bit of air can cause overheating issues.

Mark

[DotDun]

Originally Posted by colemj

In 14 years with a separate thruhull instead of the saildrive intake, we have never had air lock or ventilation problems.

Even if one occasionally drew in air (lifting a hull while motoring?) it is not a problem as it will pass through the system immediately. Raw water circuits are actively pumped and do not have air trapping spots in them.

The fresh water side is different - it uses a passive circulation pump and has air traps - that is where a little bit of air can cause overheating issues.

Mark

Correct! If your raw water system gets air locked, you have other issues that need addressed (pump sucking air from bad lip seal, etc). Rubber impeller pumps used on raw water systems are self-priming, occasional air getting into the system is not a problem.

With that said, one advantage of getting raw water from the saildrive is due to pulling water from ~10" deeper than a thru-hull. At this depth, it's less likely you'll suck in grass. Of course, just don't transit through those floating hay fields is another way to keep grass from plugging in the strainer.

I've been using raw water from the saildrives for 9+ years with no problem, but I'm ready to abandon it at the first sight of an issue. I revisit the idea at every haul out, but I'm one of those 'don't fix it if it ain't broken' types. The biggest irritant is the stupid brass gate valve that Yanmar uses, I swear it's pure brass the way it corrodes.

[tpkas]

Jacana,

Just recently we had very poor water flow through the tell tale. I'd only recently replaced the impeller so figured the problem was between the impeller and the saildrive water intake. I checked the raw water strainer , it was clean and left the lid off. I then disconnected the intake hose at the pump input and blew back through the hose towards the raw water stainer. As I was lying on the engine at the time this blew salt water all over my head .... reconnected the hose to the pump ... got towel for wet hair I then took the hose from the strainer input off and blew as hard as I could a few times back down the saildrive leg. Reconnected the hose and put the lid back on the strainer. Started the engine and after a few moments the water flow was excellent .... must've been a partial blockage of the saildrive leg.

I'm now thinking about putting in a Y valve in between the saildrive seacock and the raw water strainer so if the problem occurs again I can simply and very quickly open the Y valve and blow down the saildrive leg.

Regards,

Brian

[Jacana]

Hi Brian,after beaching then trying to clean up inside the legs I blew through the hose and little bits and pieces of shell etc came out however I still don't get enough water coming through on 1engine to keep cool enough to run at higher than 1000 rpms.

[Gordon]

Hi Brian,
On the Orana with the D2-40 engines we experienced reduced water flow and steam out the exhaust. The problem was quickly fixed by getting a piece of stiff wire, an old wire coathanger actually, jumping into the engine bay with this and the appropriate screwdriver, then turn off the inlet sea cock remove the inlet hose, use the wire to then poke down thru the sea cock which you have now opened and this should clear the shell and other life blocking the water flow. There will be a little water come in but this is quickly sponged out with the shell waste etc.
You quickly become used to checking the exhaust flow and will note the steam with the reduced flow if there is a blockage.

Cheers Gordon.

[DotDun]

Originally Posted by Jacana

Hi Brian,after beaching then trying to clean up inside the legs I blew through the hose and little bits and pieces of shell etc came out however I still don't get enough water coming through on 1engine to keep cool enough to run at higher than 1000 rpms.

The best way to clean the saildrive leg is with phosphoric acid. A commercial product to do this is Barnacle Buster. Either let is soak or rig up a pump in a bucket and circulate it.

[Cotemar]

Pulled into Block Island, RI this weekend and had to anchor with one engine with 22 knots of wind blowing.
Was not too bad. Just had to keep the boat moving to steer.
Not sure when we picked up a piece of floating line, but it held the blades closed. I had no thrust in forward or reverse.

It was getting dark as we pulled into the harbor, so I waited until morning to snorkel on it to see what happened. Most of the line came right off by hand, except for the short section that was lodged behind the prop and zinc.
Had to remove the two zinc halfs and pull the small piece of line out.

I should have replaced the zinc before the small lip wears away. That would have stopped the line from getting behind the prop. Looks like nothing touched the shaft seal. And a check of the drive leg oil looked good.

Sailed most of the 22 miles home and used the sail drive for about 20 minutes and all seems well again.

[Jacana]

Originally Posted by Jacana

Hi Brian,after beaching then trying to clean up inside the legs I blew through the hose and little bits and pieces of shell etc came out however I still don't get enough water coming through on 1engine to keep cool enough to run at higher than 1000 rpms.

Problem finally solved-after cleaning every little sea water entry nook and cranny even hooking another sea water inlet direct to water pump with no change I finally pulled the heat exchanger apart,guess what 2/3 rds blocked,now motoring along 2500rpms and singing like a canary,checked and cleaned sb side about 1/3rd blocked.4000 hours and my little 3gm30s are again running like new.
Thanks for all the suggestions.
Cheers Geoff

[Edmund]

Originally Posted by tpkas

I'm now thinking about putting in a Y valve in between the saildrive seacock and the raw water strainer so if the problem occurs again I can simply and very quickly open the Y valve and blow down the saildrive leg.

A great idea, Brian!

But I would use a 3-way T-valve on top of the original seacock.
Then you would have 3 positions:

1) -open from leg to engine- normal operation.
2) -open from leg to new intake - cleaning the leg by blowing air or water down the leg.
3) -open from engine to new intake - use it as filling point for freshwater for cleaning or antifreeze for winterconservating. You would also be able to get emergency cooling water in this way, if your saildrive got really clogged.

On my 2do-list. Thanks.
Edmund

[Edmund]

Done, but with a regular valve. Works great. I can now easily flush my engines with fresh water whenever a want to, and conserving for wintertime is of course much easier.
If I should need to flush the leg I will have to take the lid of the seawaterfilter and close the inlet pipe while flushing.

[Edmund]

Two sets of Volvo 18x13 folding blade sets are finally on their way, to replace the original 17x12. Plan to mount them mid May.

Anyone who would like to buy my old ones please let me know. They are in good condition, no damages, from 2010, 380 hours/3500 Nm. Only blade sets, no hub.
Price: Around 50% from new?

[Edmund]

Originally Posted by Edmund

If I should need to flush the leg I will have to take the lid of the seawaterfilter and close the inlet pipe while flushing.

Just ********, sorry. The seawater pump do of course hold against the pressure, so flushing the leg through the new valve is just as easy as flushing the engine.

Warning:
Do NOT put high pressure through the extra valve with both the inlet valve closed, and the engine not running.
In this situation both outlets are closed, so water pressure will build up, and may blow up the filter lid.
I have just tested it, it works.

[Edmund]

18x13 Volvo 3 blade folding props mounted, to replace the original 17x12.
Results are: (boat "empty" and clean):

Two engines:
Prop: RPM: Knots:
17x12 2400 7,9
18x13 2400 8,6

17x12 3250 9,5 top
18x13 2950 9,7 top

One engine:
Prop: RPM: Knots:
17x12 2400 7,0
18x13 2400 7,6

17x12 3050 8,2 top
18x13 2650 8,2 top

We had a little breeze going during testing, so I will try again later in calm conditions to confirm.

In general I'm very satisfied with everything, except for the price....
The big question is of course how she will perform when fully loaded in heavy winds. But the good performance shown on only one engine does show there is still quite a bit of torque left to handle heavy conditions, with both engines running.

[Cotemar]

Edmund,
Looks like good numbers from the 18x13 props. When I change my blades, I will go with them also.
Nice work.