Volvo Md7a Rebuild or Repower

[grifteron]

Hi all!
I'm another MD7 nut scrounging around for parts etc. It's encouraging to see the level of interest that these motors still generate. I've got a Md7a in my boat and it goes very well starts first time everytime and goes and goes without issue of any sort. Result! and i love the heavy duty simplicity of these engines.
So, looking ahead to a time when things might not be so rosie i've aquired a spare md7a and a seized md7b. I've just managed to free up the B (head gasket fail was the root of it's problem i think) with the help of a soak in diesel Wd 40 cola and vinegar + sledgehammer. So now its apart it looks clean inside so i'm going to attempt to get it up and running. Gaskets.. found a place in sweden called Crom Marine.. full set of for around 170 dollars or de-coke set (head, exhaust etc) for around 80 don't know how that compares with US prices. Helpful staff aswell. Today i'm going to pull out the piston that was seized and see what the ring situation is. The Greek seller on ebay is the most cost effective i've seen so far..so eyes peeled for bargins.
As an aside..can anyone confirm the differences between the A and B models. I've been told its only the injector pump that differs.
Ok i'll be popping in to check developments.
Good luck!

[gjordan]

Grifteron, I took a quick trip round the internet and found that the MD7A and MD7B take the same block, so I would assume (as dangerous as that can be) that the bore and stroke are the same. The biggest thing I noticed was that it turns up to 3000 RPM, which that alone could account for the additional 4 HP. That would be a different, or differently adjusted injection pump, so what you were told may very well be true. It sounds like you have spare parts for a lifetime. Best of luck. ______Grant.

[hpeer]

Grant,
I went to Volvopenta workshop.com and for f the same part number for piston for both the 7a and 7b. But the injector pumps have different numbers.

Didn't look beyond that.

Safar is having a hissy fit and won't let me past links.

[manitu]

Ok.. MD 6/7 was designed by swedish Albin Motors in 1970 and was originally called albin X-2.

MD6A was delivered with a 100s saildrive, MD6B had a 110s saildrive (from Volvo)
Both rated at 10hp/2400rpm
MD6A had a dynastarter , MD6B separate starter and alternator.

MD7 had a larger piston but the same stroke as MD6. MD7A:110s saildrive,13,4 hp/2600rpm. MD7B: 120s saildrive, 17,5hp/3000rpm.

A little oddity: Volvo does not measure hp at the crank , but at the propshaft!
Another one: The engine serial numbers runs in one series for MD6-MD7!!
MD6A starts at nr. 100, MD6B at 8000, MD7A at 10975 and MD7B at 32550.

This engine is said to be the best volvo engine ever made , and like most small green engines , not designed by volvo...

Install Manual:
http://nf.broach.se/motorer/volvo-pe...on_sve_eng.pdf
User Manual:
http://nf.broach.se/motorer/volvo-pe...ion%20Book.pdf
Workshop manual:
http://nf.broach.se/motorer/volvo-pe...p%20Manual.pdf

.manitu

[hpeer]

Great info, thanks.

[jeffjd]

Working on the engine now. Exhaust manifold check out to have no leaks. The compression test with the proper tool is 340 😄.

Now what. Still have the white exhaust. I will start checking the fuel system.


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[Cheechako]

Well, things are looking up anyway!

[hpeer]

How did you come by the tool?

[hpeer]

I'm not sure if this is kosher, if not mods can kill it.

I found some other posts of interest on MD7's that I will post here. May be a it out of context.

Parting Out Volvo MD7A - SailNet Community

I am interested in the manifold in any condition, as I know how to remove the internal clogs & blockages. The problem is with the water main entrance hole at the bottom of the manifold. The channel between this entrance and the inner manifold volume is very small and easily blocked. You have to drill out two of the tapped holes holding the exhaust elbow flange and then drill a special hole in the body from which the blocking material is removed. This extra hole is then plugged with a screw, after tapping it.


, it is MARTEC International, Karlbergs Strand 4, S-171 62 Solna, SWEDEN, TEL. +46 8 826610 FAX +46 8 832540

SITE:
Martec - Martec / Volvo Penta

Kit model No. 901 - 1011

I have been installing fresh water cooling kits by Martec since 1987 on several Volvo motors and even on one old Yanmar and they reliability is excellent. I never had any problem. They use a Johnson Pump electric pump and have the added advantage water starts circulating as soon as you turn the key and keeps circulating when you stop the motor until you turn off the key. This feature allow water cooling inside even after you have stopped the motor thereby bringing temperature down and minimizing deposits in the heat exchanger.

Do try to revive your MD7: it is a fantastic little motor and as long as you use it regularly, use fresh water cooling and do regular maintenance it will last forever. If you let it stand for more than a few months then the injectors tend to clog (3 holes per injector) but with the cleaning kit (micrometric stainless steel wires) you can clean them yourself, or Service will clean them in the ultrasonic bath.


Volvo Penta MD6b Cold Start System - Page 4 - SailNet Community


website for the starter rebuilder - he did a great job at a low price

Buckeye Auto Electric if you have a Volvo starter ( probably Atomic or Westerbeke too) just ship it to him


Need Volvo MD6 Parts - SailNet Community

The MD6A&B models are virtually identical. And because this version of the Volvo small block diesels had such a short-lived ('75-'76) production run, it's almost impossible to find parts 37 years later for a cast exhaust manifold. I'm still able to find regular seals/impellers/filters/etc (small parts) for the motor.

I was able to track down a company on the east coast, French Creek Marine (NY), that made SS manifolds as an aftermarket replacement, but they're retailing for ~$1500.



milky oil in a volvo md7 - Page 3 - SailNet Community

Good thread on replacing a water pump, a joy if you've not done it.

MD6A compression test adaptor.. - SailNet Community

Source for compression adapter

[jeffjd]

Can someone with a md7a cav injector pump tell me what it sounds like at idle, 1/2 throttle and full throttle ?

Mine makes a ticking noise and I thinking that may be an issue. I am running out of options.


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[barnakiel]

There is no clicking on our boat. If I get real close to the pump (without having my head torn off by the fly wheel) I can hear the pump makes its own tick tack work (I am not sure this comes from the pump or from another element in the same area). But when I stand up in front of the engine, I cannot hear it even at idle.

I can hear the valves pretty clear though.

If you youtube there are MD7 at work videos there - perhaps they will give you a clew ooooppps clue.

Volvo Penta MD7 MD-7 - YouTube

Volvo MD7A Marine Engine - YouTube

Volvo Penta MD7B Cold start and run. Dreamfactory. - YouTube

Ours sounds like the top link. The other ones (esp the second one) sound smoother.

b.

[gjordan]

The second engine shown in the youtube video has the SENDURE fresh water cooling system on it. You will notice the extra pulleys, one on the hand crank, and one on the fresh water pump over on the right hand side of the engine. The SENDURE has the advantage over the MARTEC in that you dont need electricity(Martec uses a 12 volt water pump) to make it work. MARTEC has the advantage over the SENDURE in that if your starter packs up, you still have the hand start available. I think they are both good systems. ______Grant.

[gjordan]

weephee, and/or grifteron, have you folks had a chance to look and see if there are any manufacturer data, or part numbers on the backs of the rod bearing shells? It sometimes takes a magnifying glass, and a bright light to read the inscribed letters. I am still horrified at the thought of $400 for a set of rod bearings, and am sure there are some economical replacement if we can locate them. ________Grant.

[jeffjd]

Originally Posted by barnakiel

There is no clicking on our boat. If I get real close to the pump (without having my head torn off by the fly wheel) I can hear the pump makes its own tick tack work (I am not sure this comes from the pump or from another element in the same area). But when I stand up in front of the engine, I cannot hear it even at idle.

I can hear the valves pretty clear though.

If you youtube there are MD7 at work videos there - perhaps they will give you a clew ooooppps clue.

Ours sounds like the top link. The other ones (esp the second one) sound smoother.

b.

Mine sounds like the top video also. Thanks - I won't worry about the tick tack of the pump.

Oddly enough my valves are pretty quiet.


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[Greg Y]

I so feel your pain!

I bought a boat with a poorly running 25year old MD7A ten years ago. I think I have fixed, replaced, rebuilt and been stranded far too many times to recount. I even replaced the engine with a fresh water cooled one once. I finally had enough. That engine is a workhorse for sure, not dissing the MD7A. It will last forever if you maintain and repair it enough. But how much time do you want to spend working on your engine and how much time do you want to spend at sea?

As for value of your boat and maybe replacing her....I certainly thought about that too. Why buy someone else's problems? Any used boat you buy for what you can afford will just have tons of issues you will need to address....like another bad engine. You likely have all that addressed and figured out on your vessel.

I repowered with a Beta 14. I chose that after much research. Two things that made the decision for me were googling "MAKE MODEL engine problems" for all the various brands. The number of hits for a question kind of says it all! That and the fact that Beta will give you engine mounts that adapt perfectly for the Volvo. They fit with less than 1/16th offset.

I also sold my old MD7A to someone. (Hi Grant, how is the engine coming along, by-the-way?)

I have never felt more happy and more relaxed on my boat as I do now. Ten years of working on that MD7A was a learning experience for sure. One I don't regret really. But wow....it sure is nice to be fully relaxed and not always worried about what was going to break/wear out next. My boat is cleaner (emissions wise and bilge), way faster (picked up 2 full knots) and I am spending more time out enjoying the whales and scenery.

Sorry to be the only one to support re-power, but I just cannot express how pleased, relaxed and confident I am now on my boat. She was my nasty girl, now she's my mistress again!