Volvo 120S Saildrive Raw Water feed

[jpd85]

Hi,

I have a Volvo 2001 with a 120s Saildrive leg that is Raw Water Cooled through the saildrive leg.
The engine has started overheating and I am trying to work out where/what the problem is. I suspect the bockage is between the raw water pump and the water intake holes in the leg as I think the amount of water coming out of the exhaust is less than it was. I measured the water flow from the pump with the engine off and the seacock(blue wheel type) open. It was about 400ml in 1 minute. Anyone know if this is too little? Unfortunately I haven't measured it when everything is ok to compare.

Thanks

 

[scottie]

The 120 drive is used with many bigger engines so should have plenty capacity for 9hp

The main water inlet is the vertical hole at the bottom of the housing not the slots
The tube can and does get blocked with crustations
You may be able to clear some blockages with a dinghy pump from the inside

Have you checked the tube that runs inside the cyl head and when you open the cyl block drain is it running well if not you may have silting in the block
It is also worth checking the exhaust elbow flow.

 

[colhel]

How did you check water flow with the engine off?
Genuinely curious as I have the same set up as you.
Could the thermostsat be stuck?

 

[Tranona]

These engines are prone to overheating - probably nothing to do with the saildrive or raw water supply. Usual problems need to be dealt with first and that is airlocks in the raw water supply, water pump impeller and blocked heat exchanger. If you are getting reduced flow out of the exhaust, it must be in the raw water system rather than the engine coolant. To eliminate the saildrive intake, connect the input hose up to another seacock such as your loo intake if nearby.

 

[colhel]

Sorry I'm a little confused now (easily done) . I didn't think the 2001 had an option of a heat exchanger and assumed the "raw" water was the coolant.

 

[Tranona]

Sorry I'm a little confused now (easily done) . I didn't think the 2001 had an option of a heat exchanger and assumed the "raw" water was the coolant.

Yes, sorry, if it is raw water cooled (should read the whole post) then ignore the heat exchanger bit. Still not likely to be water supply but more blocked waterways or exhaust injection point.

 

[Slowtack]

I have a 120SB saildrive and VP203 engine. It pumps about 10litres or two gallons per minute at idle speed. I gave up on trying to keep the saildrive clean and installed a new skin fitting to supplement the flow from the saildrive. Works fine.

 

[jpd85]

How did you check water flow with the engine off?
Genuinely curious as I have the same set up as you.
Could the thermostsat be stuck?

The water pump is below the waterline so open it and take out the impeller. When you open the seacock water will flow into the pump and out into waiting container.

It is raw water cooled. I was hoping to confirm whether the problem is before or after the pump by making sure i'm getting the correct flow of water as far as the pump. Looking at the amount of water coming out of the exhaust I think it is less than it was before the overheating problem. Should I get about the same amount of water in through the leg as comes out of thye exhaust?(assuming running at idle speed so not overheating with steam)

I have rodded from the pump to the saildrive seacock tonight and thinkgs seem to have improved. I will try rodding up from the bottom of the saildrive leg tomorrow and check again.

Next step would then be to run the engine without the thermostat and see if it still overheats.
Thanks for all the posts.

 

[colhel]

The water pump is below the waterline so open it and take out the impeller. When you open the seacock water will flow into the pump and out into waiting container.

.

I'd be too scared I wouldn't be able to put it back together quick enough! Bit like why I haven't cleaned the paddle wheel on my log transducer.

 

[jpd85]

I'd be too scared I wouldn't be able to put it back together quick enough! Bit like why I haven't cleaned the paddle wheel on my log transducer.

The water will not flow until you open the seacock and will stop once you close it again...the log is different ;-)

 

[colhel]

Of course. What a dumbo

 

[VicS]

If you have cooling problems one of the first things you should be considering is changing the water pump impeller!. But note the earlier suggestion to check the exhaust injection point.

AFAIK the instructions are in the owners manual You can download one from http://www.volvopenta.com/volvopent...lication_search/pages/publication_search.aspx if you have mislaid your copy.

there is also a workshop manual for the 2001 2002 series at http://www.bluemoment.com/downloads.html

 

[jpd85]

Thanks for the links Vic always handy to have them online aswell as at home.
I changed the impeller when I noticed the problem first but it didn't make any difference. The old impeller didn't show any signs of wear but best to rule out the obvious first.

 

[vyv_cox]

Overheating problems on raw water cooled engines are often due to deposits on the water passageways in and around the engine block.

I'm not an expert on Volvos but I am advised as follows: Look at this page, scroll down to three photos of Volvo engines. The third one shows the water pump and injector. Removing this will reveal a perforated brass injector tube which will be encrusted with salts. Clean these out, along with any other deposits in there. Some owners drill these slightly larger to improve coolant flow but someone else may be able to advise drill sizes.

In the second photo down you will see a pipe with a double right angle bend connecting the cylinder head to the exhaust manifold. This is connected to the aft end of the perforated pipe, and also becomes encrusted with salt sludge.

Please take some photos when you do the job, for the website!

 

[jpd85]

It's fixed!
I rodded down from the seacock on the saildrive leg and between the leg and the pump and the water flow has increased. It was about 350ml per minute and is now at about 500ml per minute. Will definitely look at putting in a separate skin fitting and a filter over the winter.

Thanks again for all the tips.

Vyv, next time I need to clear that pipe(and I will cos it's a volvo ) I'll take some pics.

 

[PabloPicasso]

No need to put in a seperate skin fitting. Prime and anti-foul the inside of the saildrive leg. Either spray paint or use pipe cleaners (I got a pack of long ones from the pound shop meant frokiddie artwork) to do this.

But make sure to clean all the critters out first

 

[Stig]

I have had a cooling problem and after cleaning the heat exchanger and the water connection into the exhaust have finally isolated the problem to the sail drive inlet.

Last time I had the boat out of the water I rodded out the saildrive from below with a coat hanger. There were mussels in it! Managed to break them up where I could see them but how do you know if you have got everything out above the holes in the side of the sail drive up to the seacock? Is it possible to rod down from the sea cock with a coat hanger?

If possible I need to do this while afloat.

 

[jpd85]

I have had a cooling problem and after cleaning the heat exchanger and the water connection into the exhaust have finally isolated the problem to the sail drive inlet.

Last time I had the boat out of the water I rodded out the saildrive from below with a coat hanger. There were mussels in it! Managed to break them up where I could see them but how do you know if you have got everything out above the holes in the side of the sail drive up to the seacock? Is it possible to rod down from the sea cock with a coat hanger?

If possible I need to do this while afloat.

Yes this is possible. I did it while afloat. Take off the pipe that runs from the water pump to the inlet on the leg at the inlet. Then open the seacock and rod down. Water will come in but the flow wasn't huge on ours but we had a bung ready just in case the seacock wouldn't close again.
Our inlet seacock as a 90 degree turn on it so it was tricky to get around this initially. I think volvo replaced this with an inline seacock on later models which makes this easier.

Doing this cured my overheating. The only thing was that because it was afloat I don't know how much crud was removed. Ideally if we did this while dried out we would see what the blockage was from what fell down the saildrive leg.

 

[Bav32]

my previous boat had a raw water cooled 2002 , just the 2 cylinder version of this. they were renowned to the passage ways in the cylinder block and head getting clogged up.
Quick way to check is to slacken off the drain on the side of the block. If no water try removing the fitting completely and clearing with a screwdriver etc. If you see lots of gunge on the screwwdriver the block is probably well clogged up.

How to fix? Some people have used brick acid ; strong stuff , always works but treat with care.
Others buy expensive stuff from the chandlers.
For a first try I would go for Screwfix's own brand of central heating cleaner. Won't break the bank either!

 

[cbsura]

I had a similar issue this season with a Vovo MD2020D and 120S saildrive. Last year I would get steam out of the exhaust at 3000 rpm (but fortunately not enough for the temperature alarm to go off). This season it happened at 2800 rpm, and over the course of 2 weeks would steam at only1500 rpm. During the winter I had cleaned the leg from the intake hole at the bottom using a 3 foot length of 3/8" threaded rod. (Use a cheap zinc rod, not stainless steel, so you don't leave any more noble metal bits in there.)

As it turns out, my real problem was bits of jellyfish that had become trapped in the leg! Low throttle was fine but as soon as I throttled up the mass of them would clog at the through hull. The marina mechanic fixed the problem by blasting compressed air through it. Since then I can cruise at full throttle without any sign of steam.