Steam in Exhaust D2-40

[abouttime]

I've had the bubbles problem, and steam too (md22l) and as others have found, discovered it to be an ill fitting lid on the strainer. This was set so high, and was so large,  it was virtually impossible to achieve a good seal. The more I tried the more obvious it was the the rubber bit around the underlid had warped. I have to admit that in 7 years of sailing the Solent (though most sailing time was offshore) and another 9 in the Med, I have never found more than a small 'lettuce leaf' bit of seaweed in the strainer. As I was trying to get the seal sorted, a guy who was working on the boat suggested I just bypass the strainer altogether. He said that spare impellers was a better strategy than dodgy filter seals and local fishermen do just that!. I confess I did this and sailed for two years with absolutely no problems.
Eventually, I bought a smaller raw water filter (Vetus), both in terms of diameter and height. which is much easier to check and screw back down properly. No steam since. Although they are meant to be model specific, the Volvo md22 one is way too large for the flow it's likely to have to cope with.

Incidentally, saildrive mining, is a god idea. I bought a sink unblocking contraption. It is about 1.5 metres long and can be rotated via a little handle at the top. Regularly, I found all sort of slimy molluscs coming  up speared by the unblocker.

[Salty]

Because these molluscs don't work to any particular timetable, I've just purchased an exhaust temperature sensor and alarm. Intention is to fit it this coming weekend, so any rise in temperature resulting from newly arrived residents within the cooling water system, should hopefully not go unnoticed.

[Scorcher IV]

Salty, what type is it and how does it fit into the system?

[Salty]

Salty, what type is it and how does it fit into the system?

It's a NASA EX-1, though you can probably get something much cheaper from eBay.
I've not fitted it yet, but the plan is to take a live current from the push button power on/off supply on the engine control panel, with the negative going to a common negative. The display will probably be fitted into the binnacle mounted instrument panel.
As for the sensor, I will need to make a small hole through the exhaust hose using the drill bit supplied, locating it about 150mm aft of the cooling water injection. My exhaust hose is convoluted rather than plain, and following a discussion with one of the NASA engineers, it was recommended to fit the sensor between consecutive spirals of the reinforcing wire within the hose, and to build up the space between with silicone sealant.
So that's the plan, and I'll let you know how it went after the job is done, hopefully this weekend, but if not then it may have to wait for a fortnight.

[Salty]

As intended in reply 28 above, the exhaust temperature monitor system was fitted last weekend, taking a live switched supply from the push button on/off supply switch for the engine control panel located on the extreme right of the panel shown in the photo below. That live supply connected directly to a one amp fuse before being lead on to the display unit shown in the second photo below. The display was located on the main instrument panel as seen in that second photo, and in a few days will be fitted with a cover to ensure that it remains rain proof. The alternative was to locate this in a dry area such as just inside the companionway, and it may well get moved there, but I want to keep an eye on it for at least the rest of this season.
The temperature sensor was fitted into the exhaust hose about 150mm downstream of the cooling water injection. The exhaust hose on my B36 (2002) has convoluted hose, so a little silicone sealant was used to build up the space between the ridges in the area where the sensor was placed. This involved drilling through the hose wall using the drill supplied by NASA. The sensor was connected to the junction box seen in the next photo, and that was wired to the remaining two connections on the display unit.
Once connected the engine was run, but not on load at the time, and over a fifteen minute period the temperature shown remained mostly at around 16 - 17 degrees C. Increasing the revs up to 3000 brought the temperature up to 20 C, and by lowering the set alarm temperature from the factory setting of 85 deg C down to 19, resulted in the alarm sounding and proving that it worked. This was then returned back to the factory setting, but will be adjusted once the engine has been run on load for an hour or two.
The alarm makes a modest chirruping sound, enough to get ones attention while in the cockpit, but if you were on deck busy with sails or down below for some reason etc., it might possibly get missed.

[Scorcher IV]

Hi just as an update, went up to the boat yesterday and I replaced the anti-syphon valve and the sea water strainer with a Vetus unit. The clear top of the new strainer allows me to see inside. There is definitely a blockage in the saildrive, the water flow was even more reduced than normal. At tickover the water flow in and out of the strainer maintains the level, but as soon as the revs are increased the water is sucked out of the strainer by the impeller and lowers the level down to the bottom of the strainer, there was a reduced flow out of the exhaust at the same time exhaust gas. Boat comes out of the water next weekend so will know for sure then.