raw watter cooled Volvo diesel engine

[sibley]

I am considering buying an 1981 boat that has an original raw watter cooled Volvo diesel engine. Somehow it seems that an old raw watter cooled engine is just a problem waiting for an excuse to happer, but I may be wrong. Is there any way to convert it to fresh watter cooling at reasonable cost? Would it be worth the cost at this point in time? Or is it just fine the way it is? Anybody have any experience with this question that they would like to share?

[Faster]

It is possible to retrofit some engines with FWC, but unless you're doing it as a talented backyard mechanic I'm not sure the costs involved would be reasonable. You'd need the Heat exchanger, another pump, hoses, space to put it/mount it etc etc. I've seen it done to an old Yanmar by a very clever fellow, but he had access to lots of parts and/or made his own so the costs were down but the hours involved were considerable.

The other issue is that after 27 years of RWC, while you may stop any further deterioration, what shape is the waterjacket in now? Of course this does depend on the true hours on the engine too, and how well it's been looked after all this time.

[Lion35]

I have a raw water cooled Volvo that was installed in 1976 and it's still limping along. I thought about converting it but the realaility is I believe it would be better to replace the whole thing. Volvo sells the parts to convert to fresh water cooled and I know a guy who did this and is happy, but he found the kit used. Volvo part prices are very high and it would be prudent to check the price the conversion kit before buying the boat.

Time is against you with raw water cooled engines. Two years ago I pulled the heads and "decarbonized" them, but I think its only a matter of time before a jacket corrodes through.

The Volvos of that era are built heavy and thick and can last a long time, but if I was looking at a new boat with raw water cooling I would count it as a big negative.

Just my two cents...

[Rockter]

Sibley....

Well, there are diffeering opinions on this one.

I have got one, a 1977 MD17c, now 31 years old.

The motor is very well built indeed, but, as I have said many times, the price of spare parts is absoutely shocking. I will never buy another Volvo. Never.

The engine has spent 27 years in salt water, and the last 4 in fresh water.

In 1997, I had to split the barrels from the liners as one was leaking past an O-ring. It was corroded, but not too bad, and it went together ok, and has run well since.

If in fresh water, you can just about forget about corrosion as cast iron and fresh water virtually ignore one another chemically. Freshwater does freeze readily though, so beware frosts. I learned that one the hard way, at -14 degC, and a cracked block.

I thought of converting to fresh water cooling, but it needed an electrical pump as extra, the cost was high, the materials looked thin, and the coolling circuit diagram was far more complex. Raw water has a very simple circuit.... one pump.

Personally I would leave it. If it begins to take water in the oil, look first to the O-rings at the base of the liners. I will be surprised if the water jacket rusts through. It is rather thick on what is a very heavy engine.... about 780 lb on the MD17C.

Also, it is a very well-built motor. Just the spare parts is a very painful memory for me and I will never again give Volvo the chance to charge me £1300 (now $2600) for an exhaust manifold, then in 1997.

If ever you have to split the motor, send me a PM. I have some lessons learned in the one. Piston oversizes are available from Mahle (then £72 each) if you have to re-bore. Volvo will not sell them to you..... you have got to buy the liner kit (then £300, for me x3), and it is about 3 times the cost of a re-bore and new oversizes.

I found the gearbox reliable, if you always shift into gear at idle, and change the gear oil every now and again. If the final drive seal fails, again PM and I will steer you through that learning curve, three weeks long, but sealed in the end.

Rockter