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Volvo penta md6b

5K views 9 replies 5 participants last post by  Rockter 
#1 ·
Hi guys I'm new to this forum and to sailing, I have a seamaster 23 which I have had for about a year and recently bought a md6b which im hoping to put in,
i have a couple of questions if anyone could possibly help me out...
1. I dnt have a gearbox for it at the moment as I'm struggling to find one as you can imagine but is there an alternative to a volvo penta I could use?
2. I have a small oil leak coming from the hollow threaded shaft? I have a bolt in there at the moment but has any1 any idea why it is a hollow and threaded shaft at the end?
Any help on this would be much appreciated thanks guys John
 
#2 ·
ZF/Hurth gears are often matched up with Volvos. Try them.

You'll either need to provide a better description of the threaded shaft or post a picture.

Is this the OEM engine that belongs in the boat or are you modifying. The later could be an extreme project. It could cost more than the boat is worth, after buying a gear and all the proper mating hardware, shaft, prop, etc. The original prop pitch, shaft length, gear reduction ratio, etc, could be matched differently.
 
#3 ·
I have an MD7. Just looking at pics and rough specs it seems to be a 2cylinder 10hp motor. It looks a lot like the MD7.

The MD7 is, I believe, a much more popular motor. Do some research and see if you can find out if they use the same transmission. That might open your chances of finding one. The MD7A is 13hp and md7b is 17hp. They are essentially the same engine with different piston bores or sow such thing. I think they both used the same transmission.

I’m sorry but I do need to ask what prompted you to look to installing that particular engine? Hopefully you got it for free or next to.

The ME7’s are great engines, known to be bullet proof. But they are salt water cooled, leading to some corrosion issues and, being very old, some parts are extremely hard to find. And they spin left handed. Not a bad thing but most props are right handed.
 
#4 ·
Great il have a look around for a gearbox of that type. No the engine was bought for next to nothing and listed as a non runner but with a bit of tlc she starts without a problem and runs a dream, so it's been a labour of love getting it running and would really like to try in the boat. I'm told the shaft that's in the boat with be compatible with most gearboxes and I have checked measurements and shouldn't be a problem, this is all a learning curve for me and really want to attempt it with this engine,if it doesn't work out it comes out and I start again with not too much of a loss in the wallet so yeah thanks for your replies guys much appreciated.
 
#6 ·
I have a MD6/MD7 workshop manual and a MD7 parts manual.

I can find no part numbers, they just say the reduction gear (1.91:1 in MD7) is integral to the engine.

Send me a PM with your email and I’ll send you copies of these manuals.
 
#7 ·
Hi, hpeer. Saw your reply and you seem to know about MD6B engines. I have one in my Farallon 29 that had been running well till this past weekend, when water stopped flowing through. I was lucky to sail almost all the way to my slip, so the motor didn't overheat, but now I have to figure out how to fix it. These old engines don't have impellers, like new ones, but I suspect the pump might've decided to quit. Do you have any ideas or suggestions? Thanks!
 
#8 ·
Here is a link to an MD6 exploded parts diagram showing an impeller.

There are a few failure modes.
1-Impeller
2-Air leak in suction side of water line or suction side blockage
3-Blockage in the thermostat
4-Blockage in the cooling jacket/exhaust manifold

First question, Is the engine still spitting out water? If YES 1 and 2 are ruled out. If No then first look to the impeller. Then make sure you have no blockage either in your strainer or before it. Then consider uou may have an air leak in the suction side, these engines can have an issue with that.
 
#10 · (Edited)
The oil leak is the aft crankshaft seal where the crank exits. The end plate should unbolt to you can get to the orange seal. They are not expensive to replace. You might be able to get the old seal out by drilling carefully, then threading a screw in there (probably 2 of them), then levering it out. Look carefully at the condition of the shaft. It sometimes shows a wee line of rust pits that are not easy to see. The new lip seal must not be allowed to ride on top of those again. You may need to use a double-lip seal to recover the oil integrity. On no account scratch the shaft where it meets the seal or it is game-over. There is a big rubber shock absorber that mates to the end of the shaft. The shock absorber needs to engage with a big star-like bladed component that is not there at present. In turn, the gearbox mates with that via its own castellated component. Be wary of Volvo spare prices, even second-hand. Some websites want $5000 for a used 'box. For 29 years I have used a Volvo MD17C, now 44 years old.. It has been quite a learning curve.
 
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