Ransomes Marquis 4A oil drain plug

Someone has certainly given that a mauling and even if you had the “ special tool” , it would no longer be able to engage onto it. It will be a steel plug so. First try a sturdy set of “ mole / vies grips” hard onto the flats of the mauled up plug having first warmed up the area of the crankcase around it. Note that the case is made of an aluminium alloy and it won’t go red like steel before it melts, so perhaps a hot air gun rather a naked flame.

If that fails And if you have access to welding kit you could drive a suitably sized nut over the damaged square and then weld it to the nut. The heat of the welding may assist so as soon as the weld has cooled a bit , try a good fitting single hex socket onto the nut. The alternative would be a fairly substantial bit of mild steel strip - say inch by quarter and about a foot long, drill a hole just big enough to tap over the plug and weld the two together. Then use it as a lever to turn the plug enough to loosen it.

I’m fairly sure that that one of the above will sort it but if all fails, cut the plug off flush and drill it out. That would require a certain amount of finesse to find the centre and then carefully work up through the drill sizes.

Thank you Wristpin. I tried molegrips bit they couldn't get enough grip without fouling the body of the machine. I haven't got any welding apparatus, but will try heating up the plug with a hot air gun and try the molegrips again.

Regarding the tool for using on the 18'' Marquis what does it look like?

I hear what you say about the limited swinging room for the Mole grips but I would think that once the plug has moved a quarter turn or less, you could switch the grips end on to complete the loosening. The alternative is to remove the engine  - just four 1/2” AF hex head screws ( bolts!) and pull it away from the clutch shaft. That’s what I do for any serious work. 

 I’ve never seen or heard of a specific Ransomes tool for the removal of those square drain plugs. I’ve just had a look at a couple Mk4 parts lists and there’s no mention of such a tool in the tool kit sections. If there was such a thing, it was possibly considered a workshop tool tother than an owner / operator one. If such a tool existed, I’m assuming that it would have looked like an old fashioned drum brake adjusting tool fro m the days when cars still had drum brakes.

If you remove the engine bolts and lift the engine to give better access, you can then try using a stillson type pipe wrench on the remains of the plug. I think you will find that a pipe wrench will grip the plug and remove it.

Thank you for the advice. I did try heating the area but the molegrip access was still a limiting factor. In the end I tilted the mower up and drained the very black and very thick oil out - not a glamorous sight. I may possibly remove the engine for other work and then tackle the drain plug.

The only reason I mention the drain plug tool is that in the Marquis 4A operator's instructions on page 3 under routine servicing it notes removal of the plug 'with the help of the special spanner included in the tool kit'. I assumed it would be as shown in Wristpin's photo but didn't know the size and especially the dimensions due to the damage to my drain plug.

The pragmatic answer to the problem!  Even if you don’t manage to remove the drain plug, and when you get the engine running with fresh oil, I would get it thoroughly warmed up , and drain it again. It will help to shift the remains of the sludgy oil. Meanwhile, I’ve found an operator’s manual with a Reprint date of 1973 and there’s that mention of “the special spanner included in the tool kit” , however in the equivalent parts manual that lists the Tool Kit makes no mention of it.

Possibly the answer to this apparent anomaly is that over the years Marquises have been fitted with several different engines, Clinton, Villiers Mk7/10, BSA and Villiers F12, the last two  commonly referred to as Slopers, and it was quite usual for the machine to come with an additional  manual to match the engine being supplied at the time.

Your engine could be either a BSA or, after the the acquisition of BSA, by Villiers , they were known as Villiers F12s. Just to confuse matters is that the engines made by BSA had those initials cast into the crankcase cover just below the crankshaft, but after the Villiers acquisition there was a transition period while the crankcases were still marked BSA. The other obvious external change , ( and there were some internal  differences) is the type of oil drain plug. I will just observe that there was the “early “ type like yours and then later ones which were a large slightly domed, flanged, slot head screw with a sealing washer. Whether or not that change coincided with the change of ownership, I’m not qualified to answer !

Thank you Wristpin. I did think about giving the engine another change of oil after I run it for a few minutes, which I will now do.

I will measure the relatively undamaged drain plug on the other Marquis I own and see if I can source a tool similar to the one you show in your photograph.