Unfortunately, the paint on many engines makes a penetrating oil solution for bound up screws/bolts ineffective. What I have found to work is a hand held impact driver that, usually, will not "bugger" up the screw head. For me, one blow with the twist in the tighten direction (clockwise) and a second in the loosen direction (counter-clockwise) has often done the trick.I need to remove the cover on the hand crack shaft on our Yanmar 3gm30f.
The 2 screws on the cover are impossible to loosen (re the photo in which the upper screw in displayed)
Any tips on how the loosen them ?
or you could just buy a simple, inexpensive tool designed for the job.Impact and torque should do it. Get some friends and a case of beer. One holds the large square shanked Phillips .One puts a twist on the wrench or visegrips and you smack the driver handle with a hammer. A bit of forth and back in the torque department will help. Swearing in unison sometimes helps. If not, you've still got the beers so the day is good.
And after you break it loose using the impact driver, you can use the bit and adapter with your ratchet to back it out.
Did you try the impact drive or just move directly to drilling out the screws?I drilled out both screws with a special drill and was lucky not to ruin the threads.
The oil seal on the hand cranck shaft was leaking and I needed to remove the cover to replace it.
I have now replace the seal with a new one and hope this will stop the leak (The old seal looked OK to me).
Ah... FWIW the impact drive I referred to is manual requiring only a good sharp blow from a heavy hammer which tends to press the screw bit into the screw as well as applying the twist, which cuts down on the chance of buggering up the screw. With electric impact drivers, its sometime difficult to apply enough pressure to a screw head to avoid the problem. They do work well on bolts, however. N'any case, I'm glad you were successful and hope that resolves your leakage problem.I bought a DeWalt impact driver (had to bring my tool box up to date any way
The phillips notches were destroyed on both screws when using the impact driver. Cut a new one - which also broke.
Then there was nothing else to do than drilling out the screws. It was remarkably easy (and no cursing )
Below is a photo of the drill and the screw with the destroyed notch View attachment 34337
I can't speak to the patent issues. I can say that I have run into a lot of Frearson (also called Reed and Prince) screws on boats, particularly in good quality woodwork, including screws used to hold down the sole.FWIW, I was also told (and have not enquired further) that a lot of Japanese equipment did not use Philips screws. Electronics and camera equipment from Japan often used Reed-Prince and other screws that are very similar to Philips--but just different enough to mangle them.