D1-30 heat exchanger

[Diverphil1]

  so, we have the usual problem of corrosion on the outlet. I went to do the service and decided to clean out the exchanger, after removing the elbow found a bit of corrosion so poked around a bit to reveal the damage. The reason for doing it was the bolts to the exhaust still had paint and no spanner marks,also the Allen bolts on the rear hadn't been touched. Anyway the damage is done and needs fixing, has anyone managed to get a good weld repair when they are holed through to the coolant drain area as in the photos
Or is it destroyed and needs a 2k new bit.

Next question is the cause, after speaking to volvo they say it's the o ring's causing it to let sea water into the coolant. Every one on Internet suggests its back splash from the exhaust being blocked a bit with carbon. To be honest I can't see how water from whare the o ring seats getting to the bottom bit that's corroded. 🤔
How is the water injected into the exhaust, is it just a straight hole into the exhaust pipe or does the casting have a separate water gallery so it enters the exh flow further down the casting than whare the inlet is. (I've not seen a new one to check)
Regards
Phil
 

[Yngmar]

That looks quite rotten, although things like this have been fixed, most workshops will say no. All depends on you finding (or becoming) someone with the right skills!

Stainless Bob in Brighton can probably do it.

What does your exhaust elbow look like? Blocked up except for a small hole?

[Diverphil1]

Yes it's blocked to about 20mm hole in the middle. But that doesn't now surprise me after reading up on it,
Had the boat a couple of years and thought it's one of the 4 or 5 yrs jobs as suggested 🤔
Looking at it ,it must be the first time ever been off. No tool marks on the flange nuts or intercooler hex bolts.

[IslandAlchemy]

Welcome to the wonderful world of VP heat exchangers. They are rubbish, and eye-waterlingly expensive unfortunately.

Looks like you're going to need a new one and a new exhaust elbow too.

[Diverphil1]

 IslandAlchemy, yes it looks that way, with elbow and joints paint etc the full unit is  2150, have ordered it and broke the bank for this year, but also wondering if its worth repairing if there so good a rotting away, it will be coming off regularly in the future, and i will be able to see how the water gets in on the new one, there may be a way of modifying to help stop this happening if i can work out what's causing it, as there is no corrosion on the tubes or the mating surface groove for the o rings. leaving me thinking a longer inlet to move any water splash back further down 

[Diverphil1]

as a side note i was on here as diverphil but for some reason i couldn't log in so had to re- create the account with a new email, so hello everybody again 

[Impavidus]

Hi Mate watch our video it will explain what happens.... https://youtu.be/cNV_-Vj8IeI

[Diverphil1]

Thanks impavidus, that explains it, I've now got just over 2k of bits sat in a box 📦 waiting for me to get back down to Wales to fit them.
As its Bank Holiday this weekend I think I will wait another week to go or it will take longer to get there than it will take to put on🤣🤣

[Diverphil1]

The new parts have been fitted and it's been run up and seems to be OK, no leaks and no fog,
I have been running this at between 1800 and 2200 rpm when we have used it(other than 15 minutes out and into the marina) is that rpm about right for keeping it free of carbon as I would like to avoid this happening again. Or should I be running it harder. 🤔

[IslandAlchemy]

Around 2/3 - 3/4 of WOT rpm is what you need to run at to keep it clean.

[symphony2]

No that is the very worst way to treat a small marine diesel. They need to be run hard and for long enough to get hot. Cruising for a D1 30 is 2200-2400rpm with occasional bursts up to at least 3000rpm - you should be able to get close to 3200rpm at maximum. To give you an idea the difference it makes to run hard, I had a 2030 in a 2001 37 used as a charter boat which did typically 600+ hours a year mostly at 2400rpm. It was still on its original exhaust elbow when I sold it with 3500 hours on it.

Clearly you can't replicate that with a weekend leisure boat which does typically less than 100 hours a year, but you can help by raising the rpm and particularly the short bursts at close to maximum.

[Diverphil1]

Symphony 2, I forgot to mention usually a 5 minute burst at full belt at the end once the sails were down and heading back to channel entrance, it was more the cruising revs I was concerned about.  Will start giving it a bit more.
Thanks
Phil

[symphony2]

If you have a standard prop you should get about 5.5 knots at 2200rpm. I had the same engine in my newer and heavier 33 and found 2200 the sweet spot.

[Diverphil1]

Thanks for input everybody, all done and taken it out for a run this weekend, was getting 6.2 kn at 2200rpm and 6.8 at 2400rpm. Heading into 20kn wind but had about.0.5 knt tide with me. Standard 2 blade prop.