Volvo md2b to 2003 install?


New member
10 May 2006
Visit site
I am removing a volvo md2b and replacing it with a volvo 2003 with the ms2 gearbox, Can anyone tell me if the mounting holes are the same? Also does anyone have the dimentions, eg length of both engines with gearboxes? Im thinking i may need a longer shaft or extend the bearers as i think the ms2 gearbox is shorter


Well-known member
14 Nov 2001
Visit site
The engines are totally different in shape
The 2b has an exposed flywheel at the front and is deeper and narrower in the body
It also has an inline gearbox output.
The 2003 has a chunkier shape with an enclosed flywheel in the middle it may also have a down angle gearbox
It would make sense to check the infamous splines at this time.

It's not a slot in by any means the exhaust is on the other side and I think a different size
The propeller should be changed if you are going from 15- 28hp make sure you have enough room for it and that your shaft will take the power


Well-known member
12 Sep 2001
Home - Southampton, Boat - Gosport
Visit site
I replaced an MD1 with a 2003 (long story, but the 2003 was free) I didn't have any huge difficulties. The old 'uns are bulky, heavy lumps, so I doubt you'll have too many issues with space. Do check the length, though. Going from a single cylinder to a 3, I had to redesign the companionway steps which cover the engine, but going from 2 to 3, you shouldn't have too much of a problem.

Consider access before you fit the new engine. It may be easier to do any work to improve access to dip stick, impellor, etc with the engine out of the way.

You will almost certainly need to remove the old engine bearers. I made new ones from some "mahogany" 2X4 epoxied into place and bolted to the remains of the old ones. It isn't the prettiest job, but it seems to have worked for the last 5 years! Think about shaft alignment as you design the bearers and trry to position the engine so the output to the shaft is in the same as the old one as that will save you the cost of a prop shaft.

You may need to upgrade your water inlet. Check the pipe size.

Likewise the exhaust.

A 25mm shaft is up to the job as provided it isn't too long; I did a bit of research on shaft suppliers websites to confirm that my configuration was OK. OTOH my old flexible coupling (aged, and designed for 7HP) didn't last long!

You'll probably also want a new prop, but you can worry about that later. I ran the 2003 for several months with the original egg whisk, until I could find a second hand one of a more sensible size. You may not get the full benefit, of the extra power, but you'll be no worse off than you were before. Castle Marine's prop calculator will help you get the right one.

There will also be a fair bit of rewiring, but if you have a reasonable understanding of 12v electrics, it shouldn't be too challenging.

I found a couple of unexpected bonuses: The 2003 was so much lighter than the MD1 that I could add a dedicated starting battery and still be lighter, and I can now use a squirt of power to turn the boat in confined spaces. The old flywheel had huge inertia and the revs increases so slowly that the boat was moving before the wash over the rudder built up to turn me.

Good luck!