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DWT · 25-12-2011, 05:39

The water intake on saildrives are down on the foot of the unit. Has anyone by-passed this by installing a through hull fitting and feeding the engine this way?

Did you have to do it?

Did you just think it was a better way of water supply?

**witzgall** · 25-12-2011, 05:46

I know George on Sunspot Baby did this for both of his engines. I think he got freshwater marine growth inside the drives that clogged things up.

motion30 · 25-12-2011, 05:48

Never on a sail drive but on a high performance mercruiser this is a standard deal to bypass the outdrive where is the water pump on this?

**Cotemar** · 25-12-2011, 06:16

DWT,

You should never need to bypass the saildrive seawater inlet.

1) make sure you have a working temp gage for your engine, if not addd one.

Instruments

2) use a 12 gage piece of copper wire with a very small loop on one end and snake out all the passages once a month and when you store the boat on land.

Sail Drives and Props

DotDun · 25-12-2011, 08:21

Been sitting in salt water, 9 years old (haul out every 2-3 years), haven't had any problem. Diver cleans bottom monthly and the intake holes get clean, obviously the hollow passage way thru the sail drive doesn't get cleaned.

I was curious recently, so I connected a 5/8" garden hose and ran water backwards thru the drive @ 57lbs. pressure. It took all the water I could give it with little or no back pressure, so I figure if it can take that much water, it's plenty open enough for the small amount of water my 3GM30s require.

sailcruiser · 25-12-2011, 10:25

On my boat this was done by a PO. I never was able to obtain the reason but haven't seen problems so far. SC

**colemj** · 25-12-2011, 13:03

Yes, we have bypassed the saildrive intakes for proper throughhulls. Much better way to go - access is easier, the valves don't seize up, the handles don't rust and break, better water flow, easier to mount a strainer to, easier to clean out. And if you have a Volvo engine, this breaks the potential electrical path between the engine and the saildrive - leaving the saildrive truly electrically isolated. Also, if you have Volvo 20x0 series, the raw water pump and heat exchanger are marginal for the engine. A separate throughhull increases the water flow and reduces the potential for overheating (don't know about other series or engines).

Mark

DWT · 27-12-2011, 16:05

Quote:

Originally Posted by colemj

And if you have a Volvo engine, this breaks the potential electrical path between the engine and the saildrive - leaving the saildrive truly electrically isolated.

Mark

Mark,

I don't quite follow what your saying about an electrical path?

jackdale · 27-12-2011, 16:15

Does not a saildrive need cooling water?

DotDun · 27-12-2011, 16:17

Quote:

Originally Posted by jackdale

Does not a saildrive need cooling water?

No, it's used for a thru hull for the engine raw water.

jackdale · 27-12-2011, 16:44

Quote:

Originally Posted by DotDun

No, it's used for a thru hull for the engine raw water.

OK - I thought it also was needed to cool the lubricating oil for the drive.

Quote:

If the Sail-Drive oil temperature is too high,
stop engine immediately and check the Sail-
Drive oil level and check the oil cooler for
proper coolant and water flow.

http://marathondiesel.com/site/image...n%20Manual.pdf

**colemj** · 27-12-2011, 18:13

Quote:

Originally Posted by jackdale

OK - I thought it also was needed to cool the lubricating oil for the drive.

http://marathondiesel.com/site/image...n%20Manual.pdf

The saildrive is immersed in water - exactly like an outboard leg. The intake is simply a small throughhull that penetrates the hull flange of the saildrive to the water. No water is circulated through the saildrive from this throughhull.

Mark

**colemj** · 27-12-2011, 18:21

Quote:

Originally Posted by DWT

Mark,

I don't quite follow what your saying about an electrical path?

Volvo saildrives are electrically isolated from the engines by teflon gaskets and rubber drive plates to reduce electrolysis. Using a wire-wound hose to connect seawater to the engine intake provides an electrical connection and greater potential for electrolysis of the aluminum drive.

While this connection is weak enough that the zincs will usually take care of it, it is enough to require yearly replacement of the zincs and sometimes enough to cause more damage.

We change our zincs every 2-3 years and never have them less than 40-50% gone. I test the conductivity with a silver-chloride half cell probe, as well as general continuity test and the saildrives are electrically isolated and galvanically neutral. I have done the same tests on others connected through the water intake to the engine with different results.

Note that this is for Volvo saildrives. I don't think Yanmars are designed to be isolated.

Mark