Volvo Penta D2-40 problem

[Peter Titze]

Hi
My mechanic at the marina here can not figure out what caused the problem.
Any suggestion would be appreciated.

Engine done 220 hours and was all running well. When I started up after 3 days idddle noted white smoke comming out and oil in exhaust. A fair amount of seawater had enterd the engine my mechanic here at marine can not figured out how it got there.
After flashing out the engine and changing the oil and filter engine still running well and after running for 2 hours no more water in oil but problem unsolved.

Peter

[skipperpete]

I'm happy to hear that your engine survived being flooded. The immediate suspect would be the exhaust vent loop. Also the water pump">raw water pump can act as a shutoff valve when the engine is stopped so no siphon can occur UNTIL the impeller gets worn or loses a blade or two and then its up to the anti siphon valve to stop the water by allowing air to enter the system. Check the operation of the valve with a bit of suction, the auto ones do stick sometimes.

[Peter Titze]

Hi
Thanks for this. My mechanic here actually changed the raw water pump but aparently there was nothing really wrong with the old one. Anyway noted with the exsource pipe removed that some water is dripping out of the engine if seacock is open. Should the raw water pump stop from any water running through system?
Peter

[skipperpete]

The vent loop is the main safety device and it really needs to work properly and the raw water pump will stop raw water siphoning but not by design and only if its in pristine condition ( good impeller and no endplate wear). In a different thread about wet exhausts, an engine rebuilder mentioned that the majority of his rebuilds were engines damaged by exhaust flooding so

[Tillsbury]

There is often much talk about the dangers of a stuck siphon loop. Has anyone put two in their loop? Seems to me one could very inexpensively loop from one to another then back down. Failure of one wouldn’t matter as long as the second worked.

I’m writing this without thinking. Is there a really obvious reason why this is a bad idea or do some boats have this installed? It would only cost a few dollars...

[skipperpete]

It seems like a good idea to have 2 on the loop if they are the automatic type. A different approach is to have a small hose tapped into the loop but no valve. The hose usually runs into the cockpit or overboard at the gunwhale and will always have a small flow of water out that shows that it is clear and able to break the siphon. No flow might mean the hose is blocked (mud wasps) or the raw water pump is ailing.
None of this will save the engine from flooding by over cranking though.

[kas_1611]

I presume you have the inline raw water filter between the seacock and impeller/water pump and the anti siphon valve between the water pump and heat exchanger same as I have on my D2-40.

If I am leaving the boat in the water for any length of time I always open the filter to check it and clean it. With the seacock open this allows the water in the filter pod to drain out of the pod and down the incoming hose to the seacock. I then close the seacock and drain the hose to the water pump by taking the hose off the water pump and check the operation of the siphon, sometimes draining the hose from the water pump to the siphon too (if leaving it a very long time and over winter).

Your comment about water coming from the engine with the exhaust off and seacock open is worrying as the filter and siphon should be sufficiently above the seacock/water intake to prevent any flow. If you have water coming through then either they aren't mounted high enough or you have some "vampire" suction somewhere. Either that or it is a leak in the heat exchanger and you are seeing coolant rather than raw (sea) water.

I'd suggest good practice is to close the seacock if you are not planning on using the engine for a few days and checking the filter plus siphon are high enough to prevent flow without the pump.

[Mayaluga]

With less than 100 hours on the engine, the previous owner of our beloved boat flooded our D2-40 multiple times resulting in material damage to cylinders 4 and 3 - we are now replacing the the two pistons and supporting connecting rods to bring the engine back into service (bent/compromised con-rods) - an expensive exercise when sitting in Suva, Fiji - albeit a known issue when I bought the boat. Our S&S design places the engine below the water-line right above the keel and susceptible to flooding if the siphon loop valve is stuck. The comments in the thread are spot on to preventing this reoccurring - and the sooner the better.

[jamhass]

We use a vented loop without the popit valve. The vent line exits the hull high on the outside of the hull just under the rub rail. Easy to see and provides an excellent indication of raw water flow. Has never been an issue, and the very small amount of water "removed" from the coolant stream is negligible.