Hi All,
I recently purchased an old, 1985/87, SpaceSailer 27 with a raw water cooled Volvo Penta 2002 (2 cylinder diesel) and 120 SB sail drive.

I've an overheating issue and wish to inspect the raw water inlet that comes from the sail drive but the original inlet valve/seacock, on the sail drive is corroded open. As it's probably a globe valve, with the inlet and outlet at 90 degrees to each other it's not great as it will tend to block easily. I noted a dribble of water from the raw water pump when I checked the impeller with the corroded valve open.

Anyway, I was wondering if anyone knows what sort of thread the original valve screws into, is it a common BSP, NPT or some uncommon thread? I was hoping to have a ball valve with appropriate fittings ready to screw in when I remove the old original and inspect the internal passages.

The previous owners had extensive work on the cooling system of the engine that I've verified but as this has mainly been a Perth Swan river racer I need to check a bit further "upstream". Interestingly one of the SS27s I inspected had abandoned the raw water supply from the sail drive and converted to a through hull, also a river boat.

Thanks to anyone who may know such a specific bit of tech info.

I have a two cylinder raw water cooled Volvo and had a minor overheating problem a few weeks back. Mine is a traditional shaft drive but I'm sure there is no real difference except for the water intake. Pull the rubber hose off the output side of the water pump and crank over the engine. There should be a fairly instant flow of water into the boat. Not a great amount as the pipe is only about 1/2 an inch. If you have a good flow then the problem is further down stream. Pull out the thermostat and see if you still have one. It's probably corroded into an unrecognizable bit of rubbish. Pull off the exhaust manifold and remove the carbon build up that has blocked off the ports and the corrosion that has stopped the water flow to the head. It's all surprisingly simple and easy for the home mechanic to handle.
When it's all back together when you run the engine put a finger on the faceplate of the pump and it should always be cool to the touch. If there is a blockage the vanes will fold down and the pump body will get warm to the touch.

All the Volvo 2002 and 2003 have a common problem in that galleries into the exhaust mixer are small diameter and block with carbon.
pull of the mixer and clear the galleries.
You will get much greater water flow through the system.
This is where I would start.
I say this after having a 2003 for 15 years.
Cheers

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Ramona said..
I have a two cylinder raw water cooled Volvo and had a minor overheating problem a few weeks back. Mine is a traditional shaft drive but I'm sure there is no real difference except for the water intake. Pull the rubber hose off the output side of the water pump and crank over the engine. There should be a fairly instant flow of water into the boat. Not a great amount as the pipe is only about 1/2 an inch. If you have a good flow then the problem is further down stream. Pull out the thermostat and see if you still have one. It's probably corroded into an unrecognizable bit of rubbish. Pull off the exhaust manifold and remove the carbon build up that has blocked off the ports and the corrosion that has stopped the water flow to the head. It's all surprisingly simple and easy for the home mechanic to handle.
When it's all back together when you run the engine put a finger on the faceplate of the pump and it should always be cool to the touch. If there is a blockage the vanes will fold down and the pump body will get warm to the touch.

Hi Ramona,
I haven't checked the flow output of the pump and will do so as you suggest. The previous owners claimed to have had another manifold, elbow, thermostat and impeller fitted to resolve an overheating issue which it appeared to do for them. However for the last 6 months the motor has been used for about 15mins at a time to motor to and from the river based pen to hoist and furl sails etc so didn't get hot. It takes about 25mins before the alarm sounds. I've checked these items including cleaning out the injection elbow, which appears near new and wasn't blocked. I note the fairly small holes(2 of) and I fitted a new thermostat as a precaution finding the original appeared to work ok when I checked it. I found an issue with the alarm sensor to complicate things in that it was triggering before its rated temp of 95. I've fitted a temp gauge in its place to monitor the temp confirming it's overheating in that its getting to 100 with excessive exhaust "steaming" though it varies with speed.
Since my post I've had a swim under the boat and was amazed at the amount of weed with fronds growing on the "anti foul" right at and inside of the water inlet holes on the leg! The original valve/seacock is a poor design as it incorporates a 90 degree bend and is either a globe or needle type in construction. I note that Volvo Penta went to a sensible straight through ball valve on the later sail drives and is what I intend to fit as well as a water strainer.
Another item I want to check is the "distribution" pipe that runs through the cylinder head and has small holes to direct water through the engine proper once the thermostat opens. I used a piece of wire with a small hook and could feel some holes but I don't really know how many there are supposed to be.
Another challenge is the fitting of the engine and sail drive into my SpaceSailer 27 is such that access to, and being able to remove the inlet valve is near impossible and I will have to remove the engine to access it. As its only a little 2 cylinder I don't think it will be all that bad and I'll also add some access panels and enlarge the existing ones while its out. I also need to rehash the dodgy water lift muffler which hasn't been fitted well.
Be nice to do some sailing after all that, assuming I resolve my issue as I've no confidence in the boat as it is.

Select to expand quote

lydia said..
All the Volvo 2002 and 2003 have a common problem in that galleries into the exhaust mixer are small diameter and block with carbon.
pull of the mixer and clear the galleries.
You will get much greater water flow through the system.
This is where I would start.
I say this after having a 2003 for 15 years.
Cheers

Hi Lydia,
Thanks for that and if you read my reply to Ramona above, checking the claimed repairs was the first thing I did including inspecting the elbow as you suggest. Mine appears near new and was pretty clean and of course I cleaned what little carbon was there and yes the two holes are not that big and appears a common issue from what I've gleaned on other forums. Not just VP but can be a problem with any engine.
As a matter of interest is your installation a sail drive?
Interestingly one of the other boats I inspected originally had the same unit as mine and they modified it to a through hull raw water inlet, as I say above I believe the early 120 SB drives had a poor design valve, from a blocking perspective fitted.
Thanks again for your interest.

It sounds like a water flow problem. These engines don't have much flow through them and if you watch the exhaust outlet from the wet exhaust you should see a few squirts and not necessarily a steady flow. The exhaust elbow is unlikely to be blocked but the short running time and probably not many revs will soon build up the carbon crap in the ports. It takes surprisingly little to block the flow.
Drop off the hose after the pump first and run the engine and see how much water pumps out. Start there so you know which end the problem is at. You may have plenty of water but it is bypassing the head. Depending on how high your engine is mounted you may have a vent valve, check that this is free. The water is probably pumping OK just not getting to the right place. Check what you have compared to the workshop manual for your engine and ensure some "engineer" has not made any modifications in the thermostat area.

The PBO forums are particularly good for these sort of problems.
forums.ybw.com/index.php?forums/practical-boat-owners-reader-to-reader.13/

VicS is well worth following and he has a good webpage as well but I can't find it at the moment.

Hi Ramona,
Thanks once again.
I'll run the pump and check output as you suggest. The pump is quite small on this engine and as you say I doubt there is much water flow at the best of times.
I checked out the PBO forums and much useful info there to follow up on as well.
It appears a common issue with the 2000 series engines.
I checked the elbow and cleaned it, finding it wasn't that bad. When you refer to ports in it I assume you mean the holes inside the elbow where the cooling water is ejected into the exhaust? On mine there were two of them roughly rectangular in shape.

No I mean all the passages from the thermostat back. Have a look at an exploded diagram of your engine and see where the water has to flow and make sure you can see the same on your engine. This will probably mean pulling off the exhaust manifold off and scraping all the scale and crap out. Plenty of Youtube videos on 2002's. This one gives some idea of the water flow they should have.

Hi Ramona,
FYI I performed a flow test on the pump finding the output to be approx 350ml/min ie about a cup and a half! Looking at a Johnson pump catalog with an impeller of the same diameter, width etc the flow should be about 5 litres /min at approx the same RPM. I removed the impeller to make sure it wasn't moving on the drive hub and there is a pathetic drip out of the pump body which is below the water line.
I removed the engine to access the original Volvo Penta sea cock on the sail drive and found the valve to be full of a very hard brownish calcium or whatever deposit. For good measure the valve was not fully open and frozen in position by the mystery deposit.
I was game enough to remove the valve to be rewarded with a fountain of water gushing into the boat, usually bad but for me was very joyful!
It also proves the passages inside the sail drive leg are clear.
My next trick is to block the passages off underwater and clear out the passage from inside the boat and install a new ball valve and water strainer etc.
The photo is not great but you can see the brownish material.
I look forward to doing another flow test once its all back together!

Thank you all. I also have seacick problems with a VP 2002 120s. However it resists removal from the sail drive. I would value advice on how to do this without breaking it off.!

Sorry. Seacock - not seacick.