Engine on CD 30

[Steve Linkinhoker]

I am looking for some information on the engine in my CD 30,hull# 241. I believe the engine is a Volvo Penta MD7A, but the specs I have on the MD7A show only one belt driven pulley and I have two, one which I believe could be the raw water impeller. Does anyone know if this engine has 2 impellers? I know where the cooling impeller is ,but I thought there has to be a raw water impeller some where. Could it be in the V-drive since the raw water enters there first? The CD30 I own is a V-drive engine and I have found no info on V-drives anywhere for Volvo Penta marine engines. Not being a marine diesel mechanic, I need more info to properly maintain my engine

[Queen Elvis]

Is it possible the 2nd pulley is to drive a 'fresh' water pump? I am in the process of replacing a siezed Volvo MD2B with a rebuilt one. The previous owner of my boat added a heat exchanger system so my engine is cooled by fresh water (actually anti-freeze just like in a car). My raw water goes the heat exchanger where it cools the fresh water, and then goes back out to the sea. This raw water is circulated by the Volvo-supplied pump installed on the stern end of the engine. A 2nd pump was added to the forward side on my engine, and is not standard as far as I can tell. Remember, though, it’s a different model so yours might be different. My other pulley is to drive the alternator.

Do you have a heat exchanger? If so, that would indicate you have a fresh-water cooled system (or half-system, where the exhaust is still raw water cooled. This is very common.)

I just figured all this out yesterday when I realized I had no way to install the fresh water pump on my rebuilt engine. I now have to add a 2nd pulley somehow, but you're not in that situation by the sound of things. You already have your pulley, I think.

(I have a post on marineengines.com in the 'Miscellaneous marine engine related topics' forum entitled 'Adding a second pulley to the flywheel' if anyone would like to help me with suggestions. Basically, instead of starting to take parts off my newly rebuilt baby to install this 2nd pulley, I'm considering adding it to the flywheel.)

You also might find answers on marineengine.com - give it a try.

And get the Peter Compton book Troubleshooting Marine Diesels. It was a huge help to be me in understanding this stuff. Clear diagrams and simple text. My kinda how-to book! And wonderful suggestions for maintenance, and steps to follow while troubleshooting. I'm going to get a second copy to leave on my boat.

Hope this helps.

Malcolm

[Ron M.]

I doubt you have an impeller in your raw water intake.
The 2nd pulley was probably added to run something else, aux. pump for water or bilge. Or even a 2nd alternator.
Your v-drive is most likely a Walter. Most CD30's had this transmission, be it a Volvo or Yanmar engine.
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MERCEDES-BENZ TN

[Queen Elvis]

Correction – my additional pulley is used to drive my raw water pump, not the fresh water pump. The existing pump, situated just above my transmission was originally for raw water, but now circulates the fresh water. The Volvo workshop manual refers to it by its original use (raw water pump), hence the error in my earlier post.

And Ron, my raw water pump does indeed have an impeller. Should I look at changing this for another pump altogether? If so, what?

And Steve, I know you have a different Volvo, but I have scanned my MD2B workshop manual and would be happy to share it, if you think it would be of any use to you. Let me know….

[Steve Linkinhoker]

Thanks Malcolm. I do have a cooling system driven by an impeller. I also have a hot water tank that I believe can be heated by the engine. I think you are right that only the exhaust is raw water cooled, but there must be something driving the water. The raw water enters the v-drive so maybe there is something in there that drives the water. I'll get that book you suggested and look some more for that v-drive online.

Steve