Volvo D2 55 - smoky exhaust, lowish water flow

[dunedin]

As title says, have a Volvo D2 55 which normally runs perfectly (MDI willing!).
Now seem to have lowish water flow, resulting in clouds of white smoke when running engine. Also sounds slightly “rorty” at low revs, but other than smoke sounds fine when running.
This happens
This happened once before around 7 years ago - but that was after been lying in French marina for a few years and saildrive clogged with shellfish- ridding the seacock fixed.
This time boat has just been relaunched and very small amount of shellfish in saildrive was cleared out.
Have checked so far:
- impeller (new Feb) is fine
- take off inlet pipe and decent water flow in through seacock (messy!)
- found slight crack in Vetus filter lid and replaced lid, well sealed, but that isn’t the cure
- no water leaks into engine tray

Also have an anti siphon valve, with dribble pipe, but no water coming out of it

Thoughts as to what else might cause this?

Thanks

 

[dankilb]

Exhaust elbow carbon-ed up and blocked at the injection point perhaps?

 

[dunedin]

Exhaust elbow carbon-ed up and blocked at the injection point perhaps?

I feared somebody might say that! Can this cause it?
Any easy way of being able to confirm if that is the cause?
And how easy is this for a non-PBO type to do, as may be some weeks to get engineer to look at it (and was due to head off as winter berth now ended)?

 

[robmcg]

Exhaust elbow is a likely candidate. They are notorious for their lack of longevity. Not a difficult job to change - 4 bolts, as long as access is OK. Source new elbow from parts4engines if it is looking iffy. Use their composite exhaust gasket too as VP had a genius idea of using a stainless gasket on our MD22 which accelerates the corrosion in that area.

 

[dunedin]

Looks like you were both on the money. Can’t see how ANY water is getting through. And this is just 10 years old.

Fortunately access was only “bdy awful”, once removed air filter, not “need to remove engine, fkg impossible”

Got elbow mostly off, came off engine fine. But unable to detach from the “flexible” exhaust hose? If I can get that off then game on to order the Parts4engines s/s one.

Any brilliant ideas for splitting from the exhaust pipe?

Thanks again

 

[neilf39]

If my vetus filter cover is not absolutely airtight it makes a big difference to the waterflow as air gets sucked in. It won't leak water if it is above the waterline. Are you sure the crack in the lid is not leaking air? It doesn't take much at all.

 

[robmcg]

Push a flat headed screwdriver carefully down between the flexible exhaust pipe and the elbow. They have bonded together with rust . If you can, grab the elbow with both hands and twist and pull. Brute force required.
You have done well to get 10 years out of it btw.

 

[capnsensible]

Looks like you were both on the money. Can’t see how ANY water is getting through. And this is just 10 years old.

Fortunately access was only “bdy awful”, once removed air filter, not “need to remove engine, fkg impossible”

Got elbow mostly off, came off engine fine. But unable to detach from the “flexible” exhaust hose? If I can get that off then game on to order the Parts4engines s/s one.

Any brilliant ideas for splitting from the exhaust pipe?

Thanks again

I've sometimes had a result with a hot air gun. Off and on.

 

[dunedin]

If my vetus filter cover is not absolutely airtight it makes a big difference to the waterflow as air gets sucked in. It won't leak water if it is above the waterline. Are you sure the crack in the lid is not leaking air? It doesn't take much at all.

Thanks already replaced the Vetus lid and checked new one. The exhaust elbow is now in parts and can’t see how any water was getting through

 

[jwfrary]

Screw driver poked down the side squirt of wd, work your way around, then twist rather than pull to break the seal and then it will slip off!

 

[dunedin]

Push a flat headed screwdriver carefully down between the flexible exhaust pipe and the elbow. They have bonded together with rust . If you can, grab the elbow with both hands and twist and pull. Brute force required.
You have done well to get 10 years out of it btw.

Thanks, yes can get flat head screwdriver round about 15mm in but can’t get any leverage to remove

 

[2Tizwoz]

Thanks, yes can get flat head screwdriver round about 15mm in but can’t get any leverage to remove

Silicone grease in the gap made by the screwdriver and it may still be there when you have to push it on again.

 

[Tranona]

Cut it off and replace the short length to the waterlock.

Life has nothing to do with age - it is determined by the way the engine is used. Short runs followed by long periods of inactivity and running at light load. Boats now tend to be overpowered so the engines are never really run hard and the hydrocarbon build up gets baked solid as you will see. Well under 1000 hours (less than 10 years leisure running) before clogging up is common. On the other hand my 2030 in my charter boat ran 3500 hours in 10 years still on the original elbow. steady running for long periods at 2400rpm (50% power around 70% revs).

 

[Bobc]

This is a typical problem on boats that have an engine which is too big for the boat, but especially with VP engines. It's been common practice for the past 20 years or so for manufacturers to specify "bigger" engines, as the naive buyer thinks it's better to have an engine that's too big rather than one that's too small.

Diesel engines need to be driven hard and need to get really hot in order to properly combust cleanly, so "ticking it along at 1500 rpm" is actually doing the engine more harm than good, and this is why they coke up. They also need to be run for at least 2 hours every so often at about 2500 revs+ in order to clean them out.

Just check inside the end of the heat exchanger that there isn't any corrosion in there, as if there is, you can end up with a hole forming between the raw water and coolant systems, which is not good.

 

[dunedin]

So the Parts4Engines s/s elbow has arrived and going to try to fit it - so battle will recommence with getting the exhaust pipe off.

As others have said, the new elbow comes with a gasket to avoid corrosion.

There seems to be a metal plate between the heat exchanger and the previous elbow, which is in good condition - see photo.
This looks to be fairly attached to the heat exchanger. I assume this does not need to be removed, just add the new gasket and elbow?

PS Our boat was specced by the original owner with the higher power 55hp engine, so a classic case of being run mostly at 1,500 rpm (and done around 1,750 hrs over 10 years)

 

[dunedin]

Well the heat gun plus flat screwdriver and silicone spray got the exhaust hose off - thanks for the tips. And from there it was easy to fit the new elbow.

The bad news is that in fact the old elbow wasn’t the fault. And indeed although slightly coked, when fully removed could get a reasonable water flow through. I then went systematically back through the basics - flow through the seacock, triple checking the impeller, Vetus strainer and no leaks into bilge and stumped.

Was suggested the next place to look was “take the heat exchanger end caps off”. Took a look at this, and a YouTube video of somebody attempting to this who ended up spending a week dismantling most of the engine for access - and decided this was beyond my limits.
After an inevitable wait at this very busy time of the year the engineer visited and
- dismantled various bits to access and checked the heat exchanger, including welding rod through the tubes - his view a bit of stuff, but by no means bad by his experience, specially after 10 years / 1,700 hours
- checked water flow at final hose out of heat exchanger into exhaust elbow - which apparently was good, filling his bucket very quickly

BUT The water flow at the exhaust is still low and the exhaust steaming. Engineer had no more time so not till next week before can look at, but we are both somewhat stumped.
If decent water flow past the heat exchanger and new elbow, not many more parts to the system thereafter.

Any more ideas ?

 

[Tranona]

Have you checked the cover plate for the water pump for wear? Sounds like the pump is not pumping enough seawater and wear on the cover plate reduces flow. Pretty sure you can turn the plate over if there is wear or replace with a new one.

 

[dunedin]

Have you checked the cover plate for the water pump for wear? Sounds like the pump is not pumping enough seawater and wear on the cover plate reduces flow. Pretty sure you can turn the plate over if there is wear or replace with a new one.

Plate is in perfect nick. And as noted, the engineer tested the water flow entering the elbow and said it was fine - so that largely eliminates all the upstream stuff including the water pump

 

[capnsensible]

I've had problems on boats (various) with sea water inlet valve blocked or partially so. Stuff grows on those external inlet filters.

With bucket and sponge ready, I've disconnected hose and then opened, briefly, the valve to prove water flow. Its possible to clear some stuff with a screwdriver internally but crud on the outside obviously needs a dive.

 

[Bobc]

I think you have a partially blocked saildrive inlet.