MD7A vs. MD7B

[John M.Sullivan]

I looked at a CD30 today that has a volvo MD7B. My CD28 has a Volvo MD7A. Can one of you savvy folks out there tell me the difference. Also, the transmission appears to be facing forward. So what's up with that? Thanks for the help.... I'd love to make this move up! It has hot and cold water, (read:shower). The Minister of Finance at my house likes all of that.

[Carl Thunberg]

The CD30 came with a V-Drive, which means that the engine is mounted "backwards" with the fly-wheel aft and the transmission fore. Someone explained to me once why the CD30 was built this way, but I forgot the explanation. I know it had something to do with saving space. It might have something to do with the fact that the early CD30's had worm-gear steering, and they didn't change the engine/transmission configuration when they switched to an Edson pedestal.

So, what you saw was normal for the CD30.

[fenixrises]

Hi all,

Far as I know
A = direct raw water cooling
B = heat exchanger with fresh water cooling

It is possible to add a seperate raw water pump and heat exchanger to an "A" and make it fresh water cooled but hardly seems worth the expense involved.

Take care,
Fred

[azucha]

MD7A 1976 - 1981 was 13.4 hp at 2600 rpm, 0.77 litres
MD7B 1981 - 1983 was 17.5 hp at 3000 rpm, 0.77 litres

Volvo must have made changes to the head to get the extra power. Different valves. Larger ports perhaps on the MD7B. The MD7B runs at higher rpms (faster) to generate more power and the gearbox ratio changed accordingly.

A = saltwater cooled
B = heat exchanger, freshwater cooling.

[John M.Sullivan]

Bravo !!!! youse guyz !!! What a Board !!!! Thank you.
- John Sullivan
"Anatrina" CD28

[Jack.Ducas]

Horsepower increases stated previously are correct however the 1982 CD30 Fayaway with the "B" version is raw water cooled. FWIW.

JD

[Steve_M]

Yes, and I have an A with FWC. No idea if this was an add-on or if the ship came from the factory with FWC.

[Jerry Hammernik]

My 1983 CD 28 is a MD 7B. It is raw water cooled (freshwater since she sails the Great Lakes No heat exchanger.

I concur with the RPM figures. Although to tell the truth by the time it got to 3000 rpms, it would sound like the pistons were trying to change cylinders. I never twist it that tight.