Volvo MD1 single cylinder boat engine, some TLC required..

[Wightsparks]

This is off our small sailing boat (the big one has RR engines!) it's a late 60's Volvo MD1 puts out a whopping 5hp and weighs as much as the keel. Never worked when we bought the boat and the previous owners had installed a outboard on a drop plate on the transom, - which is horrible to use. Boat is due back in the water next week so left it to the last minute but thought I would take the lid off an have a look.

Hmm a bit of rust on the rockers, and a broken spring - which I assume was why it was abandoned.

Valve is jammed open but the bore looks OK. the top ring is stuck hard.



There is oil in it but will not turn over by hand even with the barrel off, I suspect it was left in gear to stop the prop rotating and that has seized. Next job to disconnect the cable and hammer the gear lever!

Top end parts will get chucked in the electrolysis/citric acid bath, if they look salvageable and I can find a valve spring then it might be saved.

 

[roofman]

They do live in the worst place imaginable for anything made of metal

 

[not done it yet]

Heat the piston in the oven. The ring may free off. Depends whether it is plain rusty or stuck with oil deposits.

If piston is aluminium it will expand more than the rings and that may help things to loosen up.

 

[frank horton]

seen worse......

at work we had a crawler crane that fell in at Camelairds in Liverpool......couldn't get at it for months.....
Air cooled Ruston Busyrus.....it went eventually....
still got the tools from the cab......

 

[AVI_8]

My guess is that at some point salt water has got into that.
How is it cooled? Most boat engines are cooled by salt water and if the riser manifold leaks water can get into the engine via the exhaust port and you’ve got salt water where it shouldn’t be, a common problem with poorly maintained boat engines.
Edited, just noticed your second picture and you said the cylinder was ok

 

[Keith 66]

When we bought our boat she was fitted with an MD1, back in the day 60's & 70's they were good engines. It was in a similar state & did not run as fuel pump bleed screw was snapped off,. It had had a fortune spent on it including new piston, rings & barrel liner, plus exhaust manifold & much more, Previous owner said it was still unreliable & still smoked. Today parts are crazily expensive even if you can find them. Many parts are pure unobtainium.
Cylinder heads are prone to waterways corroding through which may explain the rusty top end, I have seen at least 6 of these die this way in our club alone. Would you even find a new head? I doubt it.
First job i did when the boat came home was to rip it out, wire brushed it clean & gave it a coat of Buick green (same as volvo green), got it running & sold it for a few hundred quid.
It was replaced by a beta, half the weight & over twice the Hp.
At this age & state its in i would not even bother, rip it out & use it as a mooring sinker.

 

[jerrytug]

I had a 1970's Volvo MD3 in Marihøna, and the seals wore out on the timing-gear driven seawater pump. The sump filled up with salt water and unknown to me, the poor old thing spent a while lubing itself with seawater instead of oil, crossing from Denmark to Norway.
When I removed the sump dipstick, I was squirted in the face with boiling salt water! It still ran though, they are tough motors..
Spare parts from Volvo were extortionate or unavailable though, which meant it got scrapped and replaced by a Beta.

 

[Tinbasherdan]

As above, it’s a mooring sinker, get something in there you can trust

 

[Barking Mat]

As above, it’s a mooring sinker, get something in there you can trust

I'm 100% behind this comment.

Only suitable as an anchor.

Don't get me wrong I drive a volvo, my wife has one too.

But these engines are carp, the sleeves on the cylinders have seals at the base which fail, impossible to separate the liner from the block.

Go kubota, I recommend Nanni diesel.

 

[jerrytug]

I'm 100% behind this comment.

Only suitable as an anchor.

Don't get me wrong I drive a volvo, my wife has one too.

But these engines are carp, the sleeves on the cylinders have seals at the base which fail, impossible to separate the liner from the block.

Go kubota, I recommend Nanni diesel.

Have you got Nannies in the hire fleet, I think they are a French marinising company?
I considered one against a Beta, but the UK importers agents (somewhere in Norfolk if I remember) were rude and ignorant, compared to Beta who were helpful and knowlegable.

 

[Barking Mat]

Have you got Nannies in the hire fleet, I think they are a French marinising company?
I considered one against a Beta, but the UK importers agents (somewhere in Norfolk if I remember) were rude and ignorant, compared to Beta who were helpful and knowlegable.

I maintain a fleet of 13 Nanni's, a herd, good engines.

Beta, is what's left of Thornycroft, I believe.

 

[Barking Mat]

Thornycroft 1.5 + 2.5 litre diesel, good engines, not the 1.8.

 

[500e]

Look at Robin air cooled diesel 7.5 Hp then make up a water cooled exhaust flange.
We used one on a Albin Viggen with a swash plate pump hydraulic drive, to convert from outboard.
Made a light weight leg with direct drive hydraulic motor encased in CF & Kevlar.
Was super efficient on fuel, got rid of the 9.5HP Mercury hanging of the back with a thirst like it was in the pay of BP